Discussion:
Problem obtaining IP from a cisco router
Brad Stockdale
2007-02-07 21:17:03 UTC
Permalink
Hello all,

I've ran into an interesting situation which may or may not be
related to dhclient. It could very possibly be a configuration issue
on my end, but I cannot seem to figure out what exactly is going on...

At my office I have a Cisco 2620 router acting as the network
DHCP server. On said router, I have a mix of both static and dynamic
IP allocations. The relevant configuration is below:

no ip dhcp conflict logging
ip dhcp excluded-address 172.16.208.1 172.16.208.100
ip dhcp bootp ignore
!
ip dhcp pool 172.16.208.0/24
import all
network 172.16.208.0 255.255.255.0
default-router 172.16.208.1
dns-server 67.135.184.20 67.135.184.21
!
ip dhcp pool computer1
host 172.16.208.58 255.255.255.0
client-identifier 0100.0475.99fe.e7
!
ip dhcp pool billing
host 172.16.208.15 255.255.255.0
INSERT LINE HERE...
!

The machine that is causing me grief is "billing". No matter what I
do, I cannot seem to get the router to recognize the
client-identifier that I specify. I have tried the following configs
to see if I could get anything to work...

hardware-address 00d0.b7a9.26c2
hardware-address 0100.d0b7.a926.c2
client-name 00d0.b7a9.26c2
client-name 0100.d0b7.a926.c2
client-identifier 00d0.b7a9.26c2
client-identifier 0100.d0b7.a926.c2
client-name "billing"

I forget any other ones...

In the dhclient.conf file, I have tried specifying the
dhcp-client-identifier option to all the various iterations above. I
have also tried setting the host-name to the same values.

Here's what I'm seeing on the router:

9w0d: DHCPD: checking for expired leases.
9w0d: DHCPD: DHCPREQUEST received from client 00d0.b7a9.26c2.
9w0d: DHCPD: Sending DHCPACK to client 00d0.b7a9.26c2 (172.16.208.129).
9w0d: DHCPD: child pool: 172.16.208.0 / 255.255.255.0 (172.16.208.0/24)
9w0d: DHCPD: pool 172.16.208.0/24 has no parent.
9w0d: DHCPD: child pool: 172.16.208.0 / 255.255.255.0 (172.16.208.0/24)
9w0d: DHCPD: pool 172.16.208.0/24 has no parent.
9w0d: DHCPD: child pool: 172.16.208.0 / 255.255.255.0 (172.16.208.0/24)
9w0d: DHCPD: pool 172.16.208.0/24 has no parent.
9w0d: DHCPD: creating ARP entry (172.16.208.129, 00d0.b7a9.26c2).
9w0d: DHCPD: unicasting BOOTREPLY to client 00d0.b7a9.26c2 (172.16.208.129).

So, it assigns it the address 172.16.208.129, instead of the hard
coded 172.16.208.15.

The client-identifiers will not match with what I have tried on the
router as far as the client-identifier or client-name or
hardware-address lines...

I have contacted Cisco about it, because my gut instinct is that the
problem is on the router, not the dhclient. After working on it for a
couple weeks on and off with Cisco, they came to the conclusion that
they didn't know what was going on and couldnt fix it.

Oh, here's a sh ip dhcp bind

Bindings from all pools not associated with VRF:
IP address Client-ID/ Lease expiration Type
Hardware address/
User name
172.16.208.3 0100.5004.d7c6.7c Infinite Manual
172.16.208.4 0100.104b.2b27.ca Infinite Manual
172.16.208.5 0100.0502.37e5.9f Infinite Manual
172.16.208.6 0100.e081.2e69.6a Infinite Manual
172.16.208.7 0100.0d60.11f4.89 Infinite Manual
172.16.208.8 0010.5aaa.8c7c Infinite Manual
172.16.208.9 0100.9027.3a4c.55 Infinite Manual
172.16.208.10 0100.0502.8e16.10 Infinite Manual
172.16.208.11 0100.6097.bbfe.e6 Infinite Manual
172.16.208.12 0010.4b21.5e02 Infinite Manual
172.16.208.13 0100.3018.a5ea.1a Infinite Manual
172.16.208.14 0100.1485.1e82.85 Infinite Manual
172.16.208.15 00d0.b7a9.26c2 Infinite Manual
172.16.208.58 0100.0475.99fe.e7 Infinite Manual
172.16.208.101 0050.04d7.c67c May 03 1993 12:26 PM Automatic
172.16.208.102 0100.c0b6.01b5.a3 May 03 1993 05:13 PM Automatic
172.16.208.129 00d0.b7a9.26c2 May 03 1993 08:06 PM Automatic

As you can see above, some of the Client-ID's have the 01 prepended,
and some do not... I cannot figure out why the router detects some of
then like that and others not. I know a Client-Identifier is partly a
microsoft invention, but even when I use the hardware-address
command, I cannot get dhclient to get the assigned address...

I was hoping that maybe someone out there has ran into this before
and can point me towards a solution or work-around.


Thanks in advance,
Brad
--
This message has been scanned for viruses and
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Rohit Jaini
2007-02-08 05:12:44 UTC
Permalink
Hi Brad,

I don't know much about Cisco routers, but looking into your mail, I have some thoughts which you can validate.

If I understand configuration correctly all the details are correct. But if you look into router table
both 172.16.208.15 and 172.16.208.129 IP leased to same Client-ID.

IP address Client- ID/ Lease expiration Type
172.16.208.14 0100.1485.1e82.85 Infinite Manual
172.16.208.15 00d0.b7a9.26c2 Infinite Manual
172.16.208.58 0100.0475.99fe.e7 Infinite Manual
172.16.208.129 00d0.b7a9.26c2 May 03 1993 08:06 PM Automatic
Tim Philips
2007-02-08 05:49:17 UTC
Permalink
Hi All,


[sorry for the lengthy e-mail below]



I'm trying to diagnose a very weird problem for a client. They several
Windows Vista clients on their network and they are having problems
obtaining an IP address via DHCP (all other Windows XP and Linux clients
are working fine).

To try and diagnose this outside of the clients production network I
have managed to replicate the problem in my personal network using my
XBOX and Nintendo Wii (based on the information below) (all other Linux,
Mac OSX and Windows clients work like a charm).

The ISC DHCP version is 3.0.1-58.EL4 (installed from RPM on CentOS 4.4).
The basic configuration for the DHCP server is as follows:

server-identifier router;
option domain-name-servers 192.168.2.1;
option routers 192.168.2.1;
option subnet-mask 255.255.255.0;
option broadcast-address 192.168.2.255;
default-lease-time 7200;
max-lease-time 50000;
ignore client-updates;
ddns-update-style none;
next-server 192.168.2.1;
authoritative;

subnet 192.168.2.0 netmask 255.255.255.0 {
range 192.168.2.100 192.168.2.150;
}

host xbox {
hardware ethernet 00:0D:3A:4E:F4:DA;
fixed-address 192.168.2.252;
}

When I enable DHCP on the XBOX and bring up the clients Ethernet
interface I see the following (as example) loops 12 times in the
messages file:

Feb 8 18:28:37 thinktank1 dhcpd: DHCPDISCOVER from 00:0d:3a:4e:f4:da
via eth0
Feb 8 18:28:37 thinktank1 dhcpd: DHCPOFFER on 192.168.2.252 to
00:0d:3a:4e:f4:da via eth0

There is no firewall between the XBOX and the DHCP server.

I have put another client (Linux) on the network and executed tcpdump
and I don't see anything coming back from the client after the DHCPOFFER
has been sent. Looking on several mailing lists and google (and
friends) it indicates that the client may be expecting some additional
options that the DHCP server isn't sending but I can't for the life of
me figure out what.

I have downloaded a Win32 DHCP client and installed that on a spare
Windows XP computer and right away the client was able to obtain an IP
address from the DHCP server, so I'm picking I have miss configured
something with the options for the given clients under ISC. I have even
attempted to set a static IP address on the client (which works fine).


Any clues that would help me solve the problem would be much appreciated!


Cheers ;)
--
Thanks
Tim Philips (RHCE)
RND GROUP LIMITED
Rudy Zijlstra
2007-02-08 08:29:52 UTC
Permalink
Post by Tim Philips
Hi All,
[sorry for the lengthy e-mail below]
I'm trying to diagnose a very weird problem for a client. They several
Windows Vista clients on their network and they are having problems
obtaining an IP address via DHCP (all other Windows XP and Linux clients
are working fine).
To try and diagnose this outside of the clients production network I
have managed to replicate the problem in my personal network using my
XBOX and Nintendo Wii (based on the information below) (all other Linux,
Mac OSX and Windows clients work like a charm).
The ISC DHCP version is 3.0.1-58.EL4 (installed from RPM on CentOS 4.4).
server-identifier router;
option domain-name-servers 192.168.2.1;
option routers 192.168.2.1;
option subnet-mask 255.255.255.0;
option broadcast-address 192.168.2.255;
default-lease-time 7200;
max-lease-time 50000;
ignore client-updates;
ddns-update-style none;
next-server 192.168.2.1;
authoritative;
subnet 192.168.2.0 netmask 255.255.255.0 {
range 192.168.2.100 192.168.2.150;
}
host xbox {
hardware ethernet 00:0D:3A:4E:F4:DA;
fixed-address 192.168.2.252;
}
When I enable DHCP on the XBOX and bring up the clients Ethernet
interface I see the following (as example) loops 12 times in the
Feb 8 18:28:37 thinktank1 dhcpd: DHCPDISCOVER from 00:0d:3a:4e:f4:da
via eth0
Feb 8 18:28:37 thinktank1 dhcpd: DHCPOFFER on 192.168.2.252 to
00:0d:3a:4e:f4:da via eth0
There is no firewall between the XBOX and the DHCP server.
I have put another client (Linux) on the network and executed tcpdump
and I don't see anything coming back from the client after the DHCPOFFER
has been sent. Looking on several mailing lists and google (and
friends) it indicates that the client may be expecting some additional
options that the DHCP server isn't sending but I can't for the life of
me figure out what.
I have downloaded a Win32 DHCP client and installed that on a spare
Windows XP computer and right away the client was able to obtain an IP
address from the DHCP server, so I'm picking I have miss configured
something with the options for the given clients under ISC. I have even
attempted to set a static IP address on the client (which works fine).
Any clues that would help me solve the problem would be much appreciated!
Cheers ;)
When you are sniffing the DISCOVER packets, take a look at which options
the client is requesting, and which options are offered by the server.
That might give you a clue.

You can also compare with the OFFER made by the Win DHCP server.

Cheers,

Rudy
shunmugakrishnan
2007-02-08 05:40:15 UTC
Permalink
Hello all,
In the configuration file, you have specified a line
"ip dhcp excluded-address 172.16.208.1
172.16.208.100". The addresses in this range are not
available for DHCP server to assign to the client.
You have hard coded this 172.16.208.15 address to
billing. But since this falls in the range of excluded
address the server is not assigning this address.

If you want to exclude only those two address, try
giving it in seperate lines
ex:
ip dhcp excluded-address 172.16.208.1
ip dhcp excluded-address 172.16.208.100

I dont know much about cisco routers, but I just went
through their documentation, and it reads
"ip dhcp excluded-address low-address [high-address]"
So I thought this might be the problem.

Am I missing something? :)

Thanks & Regards,
S.Shunmuga Krishnan
Post by Brad Stockdale
Hello all,
I've ran into an interesting situation which may
or may not be
related to dhclient. It could very possibly be a
configuration issue
on my end, but I cannot seem to figure out what
exactly is going on...
At my office I have a Cisco 2620 router acting
as the network
DHCP server. On said router, I have a mix of both
static and dynamic
no ip dhcp conflict logging
ip dhcp excluded-address 172.16.208.1 172.16.208.100
ip dhcp bootp ignore
!
ip dhcp pool 172.16.208.0/24
import all
network 172.16.208.0 255.255.255.0
default-router 172.16.208.1
dns-server 67.135.184.20 67.135.184.21
!
ip dhcp pool computer1
host 172.16.208.58 255.255.255.0
client-identifier 0100.0475.99fe.e7
!
ip dhcp pool billing
host 172.16.208.15 255.255.255.0
INSERT LINE HERE...
!
The machine that is causing me grief is "billing".
No matter what I
do, I cannot seem to get the router to recognize the
client-identifier that I specify. I have tried the
following configs
to see if I could get anything to work...
hardware-address 00d0.b7a9.26c2
hardware-address 0100.d0b7.a926.c2
client-name 00d0.b7a9.26c2
client-name 0100.d0b7.a926.c2
client-identifier 00d0.b7a9.26c2
client-identifier 0100.d0b7.a926.c2
client-name "billing"
I forget any other ones...
In the dhclient.conf file, I have tried specifying
the
dhcp-client-identifier option to all the various
iterations above. I
have also tried setting the host-name to the same
values.
9w0d: DHCPD: checking for expired leases.
9w0d: DHCPD: DHCPREQUEST received from client
00d0.b7a9.26c2.
9w0d: DHCPD: Sending DHCPACK to client
00d0.b7a9.26c2 (172.16.208.129).
9w0d: DHCPD: child pool: 172.16.208.0 /
255.255.255.0 (172.16.208.0/24)
9w0d: DHCPD: pool 172.16.208.0/24 has no parent.
9w0d: DHCPD: child pool: 172.16.208.0 /
255.255.255.0 (172.16.208.0/24)
9w0d: DHCPD: pool 172.16.208.0/24 has no parent.
9w0d: DHCPD: child pool: 172.16.208.0 /
255.255.255.0 (172.16.208.0/24)
9w0d: DHCPD: pool 172.16.208.0/24 has no parent.
9w0d: DHCPD: creating ARP entry (172.16.208.129,
00d0.b7a9.26c2).
9w0d: DHCPD: unicasting BOOTREPLY to client
00d0.b7a9.26c2 (172.16.208.129).
So, it assigns it the address 172.16.208.129,
instead of the hard
coded 172.16.208.15.
The client-identifiers will not match with what I
have tried on the
router as far as the client-identifier or
client-name or
hardware-address lines...
I have contacted Cisco about it, because my gut
instinct is that the
problem is on the router, not the dhclient. After
working on it for a
couple weeks on and off with Cisco, they came to the
conclusion that
they didn't know what was going on and couldnt fix
it.
Oh, here's a sh ip dhcp bind
IP address Client-ID/ Lease
expiration Type
Hardware address/
User name
172.16.208.3 0100.5004.d7c6.7c Infinite
Manual
172.16.208.4 0100.104b.2b27.ca Infinite
Manual
172.16.208.5 0100.0502.37e5.9f Infinite
Manual
172.16.208.6 0100.e081.2e69.6a Infinite
Manual
172.16.208.7 0100.0d60.11f4.89 Infinite
Manual
172.16.208.8 0010.5aaa.8c7c Infinite
Manual
172.16.208.9 0100.9027.3a4c.55 Infinite
Manual
172.16.208.10 0100.0502.8e16.10 Infinite
Manual
172.16.208.11 0100.6097.bbfe.e6 Infinite
Manual
172.16.208.12 0010.4b21.5e02 Infinite
Manual
172.16.208.13 0100.3018.a5ea.1a Infinite
Manual
172.16.208.14 0100.1485.1e82.85 Infinite
Manual
172.16.208.15 00d0.b7a9.26c2 Infinite
Manual
172.16.208.58 0100.0475.99fe.e7 Infinite
Manual
172.16.208.101 0050.04d7.c67c May 03
1993 12:26 PM Automatic
172.16.208.102 0100.c0b6.01b5.a3 May 03
1993 05:13 PM Automatic
172.16.208.129 00d0.b7a9.26c2 May 03
1993 08:06 PM Automatic
As you can see above, some of the Client-ID's have
the 01 prepended,
and some do not... I cannot figure out why the
router detects some of
then like that and others not. I know a
Client-Identifier is partly a
microsoft invention, but even when I use the
hardware-address
command, I cannot get dhclient to get the assigned
address...
I was hoping that maybe someone out there has ran
into this before
and can point me towards a solution or work-around.
Thanks in advance,
Brad
--
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.
__________________________________________________________
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Jeremy Bessee
2007-02-08 15:39:24 UTC
Permalink
S.Shunmuga,
The ip dhcp-excluded address just tells the router that these addresses are not part of the DHCP pool and cannot be offered. There is nothing that prevents them from being leased statically. If you look back at Brad's config, you will see that the workstation that works fine is receiving a 172,16.208.58 address, which is also inside the excluded range.

Hope this helps clarify the command.

Sincerely,


Jeremy Bessee
A+, CCNA, CCAI
Glendale Community College
Glendale, AZ USA
Post by Brad Stockdale
Hello all,
In the configuration file, you have specified a line
"ip dhcp excluded-address 172.16.208.1
172.16.208.100". The addresses in this range are not
available for DHCP server to assign to the client.
You have hard coded this 172.16.208.15 address to
billing. But since this falls in the range of excluded
address the server is not assigning this address.
If you want to exclude only those two address, try
giving it in seperate lines
ip dhcp excluded-address 172.16.208.1
ip dhcp excluded-address 172.16.208.100
I dont know much about cisco routers, but I just went
through their documentation, and it reads
"ip dhcp excluded-address low-address [high-address]"
So I thought this might be the problem.
Am I missing something? :)
Thanks & Regards,
S.Shunmuga Krishnan
Post by Brad Stockdale
Hello all,
I've ran into an interesting situation which may
or may not be
related to dhclient. It could very possibly be a
configuration issue
on my end, but I cannot seem to figure out what
exactly is going on...
At my office I have a Cisco 2620 router acting
as the network
DHCP server. On said router, I have a mix of both
static and dynamic
no ip dhcp conflict logging
ip dhcp excluded-address 172.16.208.1 172.16.208.100
ip dhcp bootp ignore
!
ip dhcp pool 172.16.208.0/24
import all
network 172.16.208.0 255.255.255.0
default-router 172.16.208.1
dns-server 67.135.184.20 67.135.184.21
!
ip dhcp pool computer1
host 172.16.208.58 255.255.255.0
client-identifier 0100.0475.99fe.e7
!
ip dhcp pool billing
host 172.16.208.15 255.255.255.0
INSERT LINE HERE...
!
The machine that is causing me grief is "billing".
No matter what I
do, I cannot seem to get the router to recognize the
client-identifier that I specify. I have tried the
following configs
to see if I could get anything to work...
hardware-address 00d0.b7a9.26c2
hardware-address 0100.d0b7.a926.c2
client-name 00d0.b7a9.26c2
client-name 0100.d0b7.a926.c2
client-identifier 00d0.b7a9.26c2
client-identifier 0100.d0b7.a926.c2
client-name "billing"
I forget any other ones...
In the dhclient.conf file, I have tried specifying
the
dhcp-client-identifier option to all the various
iterations above. I
have also tried setting the host-name to the same
values.
9w0d: DHCPD: checking for expired leases.
9w0d: DHCPD: DHCPREQUEST received from client
00d0.b7a9.26c2.
9w0d: DHCPD: Sending DHCPACK to client
00d0.b7a9.26c2 (172.16.208.129).
9w0d: DHCPD: child pool: 172.16.208.0 /
255.255.255.0 (172.16.208.0/24)
9w0d: DHCPD: pool 172.16.208.0/24 has no parent.
9w0d: DHCPD: child pool: 172.16.208.0 /
255.255.255.0 (172.16.208.0/24)
9w0d: DHCPD: pool 172.16.208.0/24 has no parent.
9w0d: DHCPD: child pool: 172.16.208.0 /
255.255.255.0 (172.16.208.0/24)
9w0d: DHCPD: pool 172.16.208.0/24 has no parent.
9w0d: DHCPD: creating ARP entry (172.16.208.129,
00d0.b7a9.26c2).
9w0d: DHCPD: unicasting BOOTREPLY to client
00d0.b7a9.26c2 (172.16.208.129).
So, it assigns it the address 172.16.208.129,
instead of the hard
coded 172.16.208.15.
The client-identifiers will not match with what I
have tried on the
router as far as the client-identifier or
client-name or
hardware-address lines...
I have contacted Cisco about it, because my gut
instinct is that the
problem is on the router, not the dhclient. After
working on it for a
couple weeks on and off with Cisco, they came to the
conclusion that
they didn't know what was going on and couldnt fix
it.
Oh, here's a sh ip dhcp bind
IP address Client-ID/ Lease
expiration Type
Hardware address/
User name
172.16.208.3 0100.5004.d7c6.7c Infinite
Manual
172.16.208.4 0100.104b.2b27.ca Infinite
Manual
172.16.208.5 0100.0502.37e5.9f Infinite
Manual
172.16.208.6 0100.e081.2e69.6a Infinite
Manual
172.16.208.7 0100.0d60.11f4.89 Infinite
Manual
172.16.208.8 0010.5aaa.8c7c Infinite
Manual
172.16.208.9 0100.9027.3a4c.55 Infinite
Manual
172.16.208.10 0100.0502.8e16.10 Infinite
Manual
172.16.208.11 0100.6097.bbfe.e6 Infinite
Manual
172.16.208.12 0010.4b21.5e02 Infinite
Manual
172.16.208.13 0100.3018.a5ea.1a Infinite
Manual
172.16.208.14 0100.1485.1e82.85 Infinite
Manual
172.16.208.15 00d0.b7a9.26c2 Infinite
Manual
172.16.208.58 0100.0475.99fe.e7 Infinite
Manual
172.16.208.101 0050.04d7.c67c May 03
1993 12:26 PM Automatic
172.16.208.102 0100.c0b6.01b5.a3 May 03
1993 05:13 PM Automatic
172.16.208.129 00d0.b7a9.26c2 May 03
1993 08:06 PM Automatic
As you can see above, some of the Client-ID's have
the 01 prepended,
and some do not... I cannot figure out why the
router detects some of
then like that and others not. I know a
Client-Identifier is partly a
microsoft invention, but even when I use the
hardware-address
command, I cannot get dhclient to get the assigned
address...
I was hoping that maybe someone out there has ran
into this before
and can point me towards a solution or work-around.
Thanks in advance,
Brad
--
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.
__________________________________________________________
Yahoo! India Answers: Share what you know. Learn something new
http://in.answers.yahoo.com/
Brad Stockdale
2007-02-08 17:26:06 UTC
Permalink
Jeremy is correct. The dhcp-excluded prevents them from being
dynamically leased.

Unfortunately, I still cannot figure out the problem that I'm
having... I've ran into this about a half dozen times over the past
six years, and it usually is with linux boxes...

I guess I'll just use a temporary fix for now -- install another NIC.

Thanks,
Brad
Post by Jeremy Bessee
S.Shunmuga,
The ip dhcp-excluded address just tells the router that these
addresses are not part of the DHCP pool and cannot be
offered. There is nothing that prevents them from being leased
statically. If you look back at Brad's config, you will see that
the workstation that works fine is receiving a 172,16.208.58
address, which is also inside the excluded range.
Hope this helps clarify the command.
Sincerely,
Jeremy Bessee
A+, CCNA, CCAI
Glendale Community College
Glendale, AZ USA
Post by Brad Stockdale
Hello all,
In the configuration file, you have specified a line
"ip dhcp excluded-address 172.16.208.1
172.16.208.100". The addresses in this range are not
available for DHCP server to assign to the client.
You have hard coded this 172.16.208.15 address to
billing. But since this falls in the range of excluded
address the server is not assigning this address.
If you want to exclude only those two address, try
giving it in seperate lines
ip dhcp excluded-address 172.16.208.1
ip dhcp excluded-address 172.16.208.100
I dont know much about cisco routers, but I just went
through their documentation, and it reads
"ip dhcp excluded-address low-address [high-address]"
So I thought this might be the problem.
Am I missing something? :)
Thanks & Regards,
S.Shunmuga Krishnan
Post by Brad Stockdale
Hello all,
I've ran into an interesting situation which may
or may not be
related to dhclient. It could very possibly be a
configuration issue
on my end, but I cannot seem to figure out what
exactly is going on...
At my office I have a Cisco 2620 router acting
as the network
DHCP server. On said router, I have a mix of both
static and dynamic
no ip dhcp conflict logging
ip dhcp excluded-address 172.16.208.1 172.16.208.100
ip dhcp bootp ignore
!
ip dhcp pool 172.16.208.0/24
import all
network 172.16.208.0 255.255.255.0
default-router 172.16.208.1
dns-server 67.135.184.20 67.135.184.21
!
ip dhcp pool computer1
host 172.16.208.58 255.255.255.0
client-identifier 0100.0475.99fe.e7
!
ip dhcp pool billing
host 172.16.208.15 255.255.255.0
INSERT LINE HERE...
!
The machine that is causing me grief is "billing".
No matter what I
do, I cannot seem to get the router to recognize the
client-identifier that I specify. I have tried the
following configs
to see if I could get anything to work...
hardware-address 00d0.b7a9.26c2
hardware-address 0100.d0b7.a926.c2
client-name 00d0.b7a9.26c2
client-name 0100.d0b7.a926.c2
client-identifier 00d0.b7a9.26c2
client-identifier 0100.d0b7.a926.c2
client-name "billing"
I forget any other ones...
In the dhclient.conf file, I have tried specifying
the
dhcp-client-identifier option to all the various
iterations above. I
have also tried setting the host-name to the same
values.
9w0d: DHCPD: checking for expired leases.
9w0d: DHCPD: DHCPREQUEST received from client
00d0.b7a9.26c2.
9w0d: DHCPD: Sending DHCPACK to client
00d0.b7a9.26c2 (172.16.208.129).
9w0d: DHCPD: child pool: 172.16.208.0 /
255.255.255.0 (172.16.208.0/24)
9w0d: DHCPD: pool 172.16.208.0/24 has no parent.
9w0d: DHCPD: child pool: 172.16.208.0 /
255.255.255.0 (172.16.208.0/24)
9w0d: DHCPD: pool 172.16.208.0/24 has no parent.
9w0d: DHCPD: child pool: 172.16.208.0 /
255.255.255.0 (172.16.208.0/24)
9w0d: DHCPD: pool 172.16.208.0/24 has no parent.
9w0d: DHCPD: creating ARP entry (172.16.208.129,
00d0.b7a9.26c2).
9w0d: DHCPD: unicasting BOOTREPLY to client
00d0.b7a9.26c2 (172.16.208.129).
So, it assigns it the address 172.16.208.129,
instead of the hard
coded 172.16.208.15.
The client-identifiers will not match with what I
have tried on the
router as far as the client-identifier or
client-name or
hardware-address lines...
I have contacted Cisco about it, because my gut
instinct is that the
problem is on the router, not the dhclient. After
working on it for a
couple weeks on and off with Cisco, they came to the
conclusion that
they didn't know what was going on and couldnt fix
it.
Oh, here's a sh ip dhcp bind
IP address Client-ID/ Lease
expiration Type
Hardware address/
User name
172.16.208.3 0100.5004.d7c6.7c Infinite
Manual
172.16.208.4 0100.104b.2b27.ca Infinite
Manual
172.16.208.5 0100.0502.37e5.9f Infinite
Manual
172.16.208.6 0100.e081.2e69.6a Infinite
Manual
172.16.208.7 0100.0d60.11f4.89 Infinite
Manual
172.16.208.8 0010.5aaa.8c7c Infinite
Manual
172.16.208.9 0100.9027.3a4c.55 Infinite
Manual
172.16.208.10 0100.0502.8e16.10 Infinite
Manual
172.16.208.11 0100.6097.bbfe.e6 Infinite
Manual
172.16.208.12 0010.4b21.5e02 Infinite
Manual
172.16.208.13 0100.3018.a5ea.1a Infinite
Manual
172.16.208.14 0100.1485.1e82.85 Infinite
Manual
172.16.208.15 00d0.b7a9.26c2 Infinite
Manual
172.16.208.58 0100.0475.99fe.e7 Infinite
Manual
172.16.208.101 0050.04d7.c67c May 03
1993 12:26 PM Automatic
172.16.208.102 0100.c0b6.01b5.a3 May 03
1993 05:13 PM Automatic
172.16.208.129 00d0.b7a9.26c2 May 03
1993 08:06 PM Automatic
As you can see above, some of the Client-ID's have
the 01 prepended,
and some do not... I cannot figure out why the
router detects some of
then like that and others not. I know a
Client-Identifier is partly a
microsoft invention, but even when I use the
hardware-address
command, I cannot get dhclient to get the assigned
address...
I was hoping that maybe someone out there has ran
into this before
and can point me towards a solution or work-around.
Thanks in advance,
Brad
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Glenn Satchell
2007-02-08 11:54:30 UTC
Permalink
Try capturing the requests from the client using tcpdump something like this:

tcpdump -n -v -i eth0 udp port 67 or 68

You're looking for the "dhcp-parameter-request-list", option 55. This
lists all the parameters that the client wants. You need to make sure
that you're specifying all of them. Probably the best way i sto look at
an outgoing packet.

In ISC dhcpd the options are given names, rather than being referred to
by a number. You can see the names and numbers in the file in the
source distribution common/tables.c

{ "dhcp-parameter-request-list", "BA", &dhcp_universe, 55 },
David W. Hankins
2007-02-08 21:33:22 UTC
Permalink
Making sure you have all (reasoanble) options listed on the PRL
configured is one good thing to try.

Another good thing is to make sure the SUBNET_MASK option appears
on the client's PRL. Some clients do not specify it, and some
servers always force it to be delivered (so clients have grown
accustomed to this). ISC dhcpd 3.0.x does not force it to be
delivered by default, 3.1.x does (at lowest priority).

Finally, make sure the dhcp server is sending the offer to the
IP address 255.255.255.255, and an all-ones ethernet destination
address.
--
David W. Hankins "If you don't do it right the first time,
Software Engineer you'll just have to do it again."
Internet Systems Consortium, Inc. -- Jack T. Hankins
David W. Hankins
2007-02-08 21:47:37 UTC
Permalink
Post by David W. Hankins
Another good thing is to make sure the SUBNET_MASK option appears
Sorry, I'm stuck thinking in C-syntax. That's subnet-mask option,
code 1.
--
David W. Hankins "If you don't do it right the first time,
Software Engineer you'll just have to do it again."
Internet Systems Consortium, Inc. -- Jack T. Hankins
Tim Philips
2007-02-09 07:28:04 UTC
Permalink
Glenn Satchell wrote:

Hi Glenn,

First off thanks very much for your very informative e-mail. I have
executed the tcpdump as suggested and get the following:

20:23:50.813845 IP (tos 0x0, ttl 64, id 17681, offset 0, flags [none],
proto 17, length: 328) 0.0.0.0.bootpc > 255.255.255.255.bootps:
BOOTP/DHCP, Request from 00:0d:3a:4e:f4:da, length: 300, xid:0xf4509737,
flags: [none]
Client Ethernet Address: 00:0d:3a:4e:f4:da [|bootp]
20:23:50.827838 IP (tos 0x10, ttl 16, id 0, offset 0, flags [none],
proto 17, length: 328) 127.0.0.1.bootps > 192.168.2.252.bootpc:
BOOTP/DHCP, Reply, length: 300, xid:0xf4509737, flags: [none]
Your IP: 192.168.2.252
Server IP: 192.168.2.1
Client Ethernet Address: 00:0d:3a:4e:f4:da [|bootp]


Once again it loops over 12 times with the only change of the id (from
the client) being incremented by 1 each time it loops.

I can't see anything regarding options from there I presume the flags
[none] is what I'm supposed to be paying attention to?


Also thanks Rudy and David for your suggestions.


Look forward to any further thoughts.


Cheers.
Post by Glenn Satchell
tcpdump -n -v -i eth0 udp port 67 or 68
You're looking for the "dhcp-parameter-request-list", option 55. This
lists all the parameters that the client wants. You need to make sure
that you're specifying all of them. Probably the best way i sto look at
an outgoing packet.
In ISC dhcpd the options are given names, rather than being referred to
by a number. You can see the names and numbers in the file in the
source distribution common/tables.c
{ "dhcp-parameter-request-list", "BA", &dhcp_universe, 55 },
Tim Philips
2007-02-09 08:18:22 UTC
Permalink
Glenn Satchell wrote:

Hi Glenn (once again),

Thanks Andy for your advice on increasing the capture size. Below is a
tcpdump of the output:

21:10:56.334328 IP (tos 0x0, ttl 64, id 19400, offset 0, flags [none],
proto 17, length: 328) 0.0.0.0.bootpc > 255.255.255.255.bootps:
BOOTP/DHCP, Request from 00:0d:3a:4e:f4:da, length: 300, xid:0x889c873,
flags: [none]
Client Ethernet Address: 00:0d:3a:4e:f4:da
Vendor-rfc1048:
DHCP:DISCOVER
CID:[ether]00:0d:3a:4e:f4:da
VC:"XBOX 1.0"
PR:SM+DG+NS
RQ:192.168.0.4
21:10:56.441805 IP (tos 0x10, ttl 16, id 0, offset 0, flags [none],
proto 17, length: 328) 127.0.0.1.bootps > 192.168.2.252.bootpc:
BOOTP/DHCP, Reply, length: 300, xid:0x889c873, flags: [none]
Your IP: 192.168.2.252
Server IP: 192.168.2.1
Client Ethernet Address: 00:0d:3a:4e:f4:da
Vendor-rfc1048:
DHCP:OFFER
SID:127.0.0.1
LT:7200
SM:255.255.255.0
DG:192.168.2.1
NS:192.168.2.1
David W. Hankins
2007-02-09 16:06:01 UTC
Permalink
Post by Tim Philips
21:10:56.441805 IP (tos 0x10, ttl 16, id 0, offset 0, flags [none],
^^^^^^^^^
Post by Tim Philips
BOOTP/DHCP, Reply, length: 300, xid:0x889c873, flags: [none]
Your IP: 192.168.2.252
Server IP: 192.168.2.1
Client Ethernet Address: 00:0d:3a:4e:f4:da
DHCP:OFFER
SID:127.0.0.1
^^^^^^^^^
Post by Tim Philips
LT:7200
SM:255.255.255.0
DG:192.168.2.1
NS:192.168.2.1
That doesn't work.

The client has to unicast their renewals to the DHCP server as
identified by the SID option.

Probably the client is smart enough to know this and doesn't bother
binding.

Possibly the client also has a firewall applied that keeps out
martians (IP source address of loopback).
Post by Tim Philips
Post by Tim Philips
server-identifier router;
I'm guessing 'router' resolves to 127.0.0.1 due to /etc/hosts.
--
David W. Hankins "If you don't do it right the first time,
Software Engineer you'll just have to do it again."
Internet Systems Consortium, Inc. -- Jack T. Hankins
Tim Philips
2007-02-09 22:34:47 UTC
Permalink
David W. Hankins wrote:

Hi David,
Post by David W. Hankins
Post by Tim Philips
21:10:56.441805 IP (tos 0x10, ttl 16, id 0, offset 0, flags [none],
^^^^^^^^^
Post by Tim Philips
BOOTP/DHCP, Reply, length: 300, xid:0x889c873, flags: [none]
Your IP: 192.168.2.252
Server IP: 192.168.2.1
Client Ethernet Address: 00:0d:3a:4e:f4:da
DHCP:OFFER
SID:127.0.0.1
^^^^^^^^^
Post by Tim Philips
LT:7200
SM:255.255.255.0
DG:192.168.2.1
NS:192.168.2.1
That doesn't work.
The client has to unicast their renewals to the DHCP server as
identified by the SID option.
Probably the client is smart enough to know this and doesn't bother
binding.
Possibly the client also has a firewall applied that keeps out
martians (IP source address of loopback).
Post by Tim Philips
Post by Tim Philips
server-identifier router;
I'm guessing 'router' resolves to 127.0.0.1 due to /etc/hosts.
You were dead right, I have used an IP address as the server-identifier
now and the clients are picking up their IP address's.

Thanks everyone for your help.

Cheers.
--
Thanks
Tim Philips (RHCE)
RND GROUP LIMITED
Jeremy Bessee
2007-02-08 18:48:08 UTC
Permalink
Brad,

I just ran through your configuration on a 2611XM, IOS version
12.2(15)T16, and it ran flawlessly. The only thing I am not able to
test is Linux. Our labs are purely Windows XP.

Sincerely,


Jeremy
Post by Brad Stockdale
Hello all,
I've ran into an interesting situation which may or may not be
related to dhclient. It could very possibly be a configuration issue
on my end, but I cannot seem to figure out what exactly is going on...
At my office I have a Cisco 2620 router acting as the network
DHCP server. On said router, I have a mix of both static and dynamic
no ip dhcp conflict logging
ip dhcp excluded-address 172.16.208.1 172.16.208.100
ip dhcp bootp ignore
!
ip dhcp pool 172.16.208.0/24
import all
network 172.16.208.0 255.255.255.0
default-router 172.16.208.1
dns-server 67.135.184.20 67.135.184.21
!
ip dhcp pool computer1
host 172.16.208.58 255.255.255.0
client-identifier 0100.0475.99fe.e7
!
ip dhcp pool billing
host 172.16.208.15 255.255.255.0
INSERT LINE HERE...
!
The machine that is causing me grief is "billing". No matter what I
do, I cannot seem to get the router to recognize the
client-identifier that I specify. I have tried the following configs
to see if I could get anything to work...
hardware-address 00d0.b7a9.26c2
hardware-address 0100.d0b7.a926.c2
client-name 00d0.b7a9.26c2
client-name 0100.d0b7.a926.c2
client-identifier 00d0.b7a9.26c2
client-identifier 0100.d0b7.a926.c2
client-name "billing"
I forget any other ones...
In the dhclient.conf file, I have tried specifying the
dhcp-client-identifier option to all the various iterations above. I
have also tried setting the host-name to the same values.
9w0d: DHCPD: checking for expired leases.
9w0d: DHCPD: DHCPREQUEST received from client 00d0.b7a9.26c2.
9w0d: DHCPD: Sending DHCPACK to client 00d0.b7a9.26c2 (172.16.208.129).
9w0d: DHCPD: child pool: 172.16.208.0 / 255.255.255.0 (172.16.208.0/24)
9w0d: DHCPD: pool 172.16.208.0/24 has no parent.
9w0d: DHCPD: child pool: 172.16.208.0 / 255.255.255.0 (172.16.208.0/24)
9w0d: DHCPD: pool 172.16.208.0/24 has no parent.
9w0d: DHCPD: child pool: 172.16.208.0 / 255.255.255.0 (172.16.208.0/24)
9w0d: DHCPD: pool 172.16.208.0/24 has no parent.
9w0d: DHCPD: creating ARP entry (172.16.208.129, 00d0.b7a9.26c2).
9w0d: DHCPD: unicasting BOOTREPLY to client 00d0.b7a9.26c2 (172.16.208.129).
So, it assigns it the address 172.16.208.129, instead of the hard
coded 172.16.208.15.
The client-identifiers will not match with what I have tried on the
router as far as the client-identifier or client-name or
hardware-address lines...
I have contacted Cisco about it, because my gut instinct is that the
problem is on the router, not the dhclient. After working on it for a
couple weeks on and off with Cisco, they came to the conclusion that
they didn't know what was going on and couldnt fix it.
Oh, here's a sh ip dhcp bind
IP address Client-ID/ Lease expiration Type
Hardware address/
User name
172.16.208.3 0100.5004.d7c6.7c Infinite Manual
172.16.208.4 0100.104b.2b27.ca Infinite Manual
172.16.208.5 0100.0502.37e5.9f Infinite Manual
172.16.208.6 0100.e081.2e69.6a Infinite Manual
172.16.208.7 0100.0d60.11f4.89 Infinite Manual
172.16.208.8 0010.5aaa.8c7c Infinite Manual
172.16.208.9 0100.9027.3a4c.55 Infinite Manual
172.16.208.10 0100.0502.8e16.10 Infinite Manual
172.16.208.11 0100.6097.bbfe.e6 Infinite Manual
172.16.208.12 0010.4b21.5e02 Infinite Manual
172.16.208.13 0100.3018.a5ea.1a Infinite Manual
172.16.208.14 0100.1485.1e82.85 Infinite Manual
172.16.208.15 00d0.b7a9.26c2 Infinite Manual
172.16.208.58 0100.0475.99fe.e7 Infinite Manual
172.16.208.101 0050.04d7.c67c May 03 1993 12:26 PM Automatic
172.16.208.102 0100.c0b6.01b5.a3 May 03 1993 05:13 PM Automatic
172.16.208.129 00d0.b7a9.26c2 May 03 1993 08:06 PM Automatic
As you can see above, some of the Client-ID's have the 01 prepended,
and some do not... I cannot figure out why the router detects some of
then like that and others not. I know a Client-Identifier is partly a
microsoft invention, but even when I use the hardware-address
command, I cannot get dhclient to get the assigned address...
I was hoping that maybe someone out there has ran into this before
and can point me towards a solution or work-around.
Thanks in advance,
Brad
Brad Stockdale
2007-02-08 19:06:16 UTC
Permalink
Jeremy,

Thank you very much for testing it. That was incredibly kind of you.

I ended up putting in another network card (a 3com) and used its
hardware address. It worked, albeit it's a bit of a kludge.

Thanks,
Brad
Post by Jeremy Bessee
Brad,
I just ran through your configuration on a 2611XM, IOS version
12.2(15)T16, and it ran flawlessly. The only thing I am not able to
test is Linux. Our labs are purely Windows XP.
Sincerely,
Jeremy
Post by Brad Stockdale
Hello all,
I've ran into an interesting situation which may or may not be
related to dhclient. It could very possibly be a configuration issue
on my end, but I cannot seem to figure out what exactly is going on...
At my office I have a Cisco 2620 router acting as the network
DHCP server. On said router, I have a mix of both static and dynamic
no ip dhcp conflict logging
ip dhcp excluded-address 172.16.208.1 172.16.208.100
ip dhcp bootp ignore
!
ip dhcp pool 172.16.208.0/24
import all
network 172.16.208.0 255.255.255.0
default-router 172.16.208.1
dns-server 67.135.184.20 67.135.184.21
!
ip dhcp pool computer1
host 172.16.208.58 255.255.255.0
client-identifier 0100.0475.99fe.e7
!
ip dhcp pool billing
host 172.16.208.15 255.255.255.0
INSERT LINE HERE...
!
The machine that is causing me grief is "billing". No matter what I
do, I cannot seem to get the router to recognize the
client-identifier that I specify. I have tried the following configs
to see if I could get anything to work...
hardware-address 00d0.b7a9.26c2
hardware-address 0100.d0b7.a926.c2
client-name 00d0.b7a9.26c2
client-name 0100.d0b7.a926.c2
client-identifier 00d0.b7a9.26c2
client-identifier 0100.d0b7.a926.c2
client-name "billing"
I forget any other ones...
In the dhclient.conf file, I have tried specifying the
dhcp-client-identifier option to all the various iterations above. I
have also tried setting the host-name to the same values.
9w0d: DHCPD: checking for expired leases.
9w0d: DHCPD: DHCPREQUEST received from client 00d0.b7a9.26c2.
9w0d: DHCPD: Sending DHCPACK to client 00d0.b7a9.26c2 (172.16.208.129).
9w0d: DHCPD: child pool: 172.16.208.0 / 255.255.255.0 (172.16.208.0/24)
9w0d: DHCPD: pool 172.16.208.0/24 has no parent.
9w0d: DHCPD: child pool: 172.16.208.0 / 255.255.255.0 (172.16.208.0/24)
9w0d: DHCPD: pool 172.16.208.0/24 has no parent.
9w0d: DHCPD: child pool: 172.16.208.0 / 255.255.255.0 (172.16.208.0/24)
9w0d: DHCPD: pool 172.16.208.0/24 has no parent.
9w0d: DHCPD: creating ARP entry (172.16.208.129, 00d0.b7a9.26c2).
9w0d: DHCPD: unicasting BOOTREPLY to client 00d0.b7a9.26c2 (172.16.208.129).
So, it assigns it the address 172.16.208.129, instead of the hard
coded 172.16.208.15.
The client-identifiers will not match with what I have tried on the
router as far as the client-identifier or client-name or
hardware-address lines...
I have contacted Cisco about it, because my gut instinct is that the
problem is on the router, not the dhclient. After working on it for a
couple weeks on and off with Cisco, they came to the conclusion that
they didn't know what was going on and couldnt fix it.
Oh, here's a sh ip dhcp bind
IP address Client-ID/ Lease expiration Type
Hardware address/
User name
172.16.208.3 0100.5004.d7c6.7c Infinite Manual
172.16.208.4 0100.104b.2b27.ca Infinite Manual
172.16.208.5 0100.0502.37e5.9f Infinite Manual
172.16.208.6 0100.e081.2e69.6a Infinite Manual
172.16.208.7 0100.0d60.11f4.89 Infinite Manual
172.16.208.8 0010.5aaa.8c7c Infinite Manual
172.16.208.9 0100.9027.3a4c.55 Infinite Manual
172.16.208.10 0100.0502.8e16.10 Infinite Manual
172.16.208.11 0100.6097.bbfe.e6 Infinite Manual
172.16.208.12 0010.4b21.5e02 Infinite Manual
172.16.208.13 0100.3018.a5ea.1a Infinite Manual
172.16.208.14 0100.1485.1e82.85 Infinite Manual
172.16.208.15 00d0.b7a9.26c2 Infinite Manual
172.16.208.58 0100.0475.99fe.e7 Infinite Manual
172.16.208.101 0050.04d7.c67c May 03 1993 12:26
PM Automatic
Post by Brad Stockdale
172.16.208.102 0100.c0b6.01b5.a3 May 03 1993 05:13
PM Automatic
Post by Brad Stockdale
172.16.208.129 00d0.b7a9.26c2 May 03 1993 08:06
PM Automatic
Post by Brad Stockdale
As you can see above, some of the Client-ID's have the 01 prepended,
and some do not... I cannot figure out why the router detects some of
then like that and others not. I know a Client-Identifier is partly a
microsoft invention, but even when I use the hardware-address
command, I cannot get dhclient to get the assigned address...
I was hoping that maybe someone out there has ran into this before
and can point me towards a solution or work-around.
Thanks in advance,
Brad
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Jeremy Bessee
2007-02-08 19:42:25 UTC
Permalink
My pleasure to help.
Jeremy
Post by Brad Stockdale
Jeremy,
Thank you very much for testing it. That was incredibly kind of you.
I ended up putting in another network card (a 3com) and used its
hardware address. It worked, albeit it's a bit of a kludge.
Thanks,
Brad
Post by Jeremy Bessee
Brad,
I just ran through your configuration on a 2611XM, IOS version
12.2(15)T16, and it ran flawlessly. The only thing I am not able to
test is Linux. Our labs are purely Windows XP.
Sincerely,
Jeremy
Post by Brad Stockdale
Hello all,
I've ran into an interesting situation which may or may not be
related to dhclient. It could very possibly be a configuration issue
on my end, but I cannot seem to figure out what exactly is going on...
At my office I have a Cisco 2620 router acting as the network
DHCP server. On said router, I have a mix of both static and dynamic
no ip dhcp conflict logging
ip dhcp excluded-address 172.16.208.1 172.16.208.100
ip dhcp bootp ignore
!
ip dhcp pool 172.16.208.0/24
import all
network 172.16.208.0 255.255.255.0
default-router 172.16.208.1
dns-server 67.135.184.20 67.135.184.21
!
ip dhcp pool computer1
host 172.16.208.58 255.255.255.0
client-identifier 0100.0475.99fe.e7
!
ip dhcp pool billing
host 172.16.208.15 255.255.255.0
INSERT LINE HERE...
!
The machine that is causing me grief is "billing". No matter what I
do, I cannot seem to get the router to recognize the
client-identifier that I specify. I have tried the following configs
to see if I could get anything to work...
hardware-address 00d0.b7a9.26c2
hardware-address 0100.d0b7.a926.c2
client-name 00d0.b7a9.26c2
client-name 0100.d0b7.a926.c2
client-identifier 00d0.b7a9.26c2
client-identifier 0100.d0b7.a926.c2
client-name "billing"
I forget any other ones...
In the dhclient.conf file, I have tried specifying the
dhcp-client-identifier option to all the various iterations above. I
have also tried setting the host-name to the same values.
9w0d: DHCPD: checking for expired leases.
9w0d: DHCPD: DHCPREQUEST received from client 00d0.b7a9.26c2.
9w0d: DHCPD: Sending DHCPACK to client 00d0.b7a9.26c2 (172.16.208.129).
9w0d: DHCPD: child pool: 172.16.208.0 / 255.255.255.0 (172.16.208.0/24)
9w0d: DHCPD: pool 172.16.208.0/24 has no parent.
9w0d: DHCPD: child pool: 172.16.208.0 / 255.255.255.0 (172.16.208.0/24)
9w0d: DHCPD: pool 172.16.208.0/24 has no parent.
9w0d: DHCPD: child pool: 172.16.208.0 / 255.255.255.0 (172.16.208.0/24)
9w0d: DHCPD: pool 172.16.208.0/24 has no parent.
9w0d: DHCPD: creating ARP entry (172.16.208.129, 00d0.b7a9.26c2).
9w0d: DHCPD: unicasting BOOTREPLY to client 00d0.b7a9.26c2 (172.16.208.129).
So, it assigns it the address 172.16.208.129, instead of the hard
coded 172.16.208.15.
The client-identifiers will not match with what I have tried on the
router as far as the client-identifier or client-name or
hardware-address lines...
I have contacted Cisco about it, because my gut instinct is that the
problem is on the router, not the dhclient. After working on it for a
couple weeks on and off with Cisco, they came to the conclusion that
they didn't know what was going on and couldnt fix it.
Oh, here's a sh ip dhcp bind
IP address Client-ID/ Lease expiration Type
Hardware address/
User name
172.16.208.3 0100.5004.d7c6.7c Infinite Manual
172.16.208.4 0100.104b.2b27.ca Infinite Manual
172.16.208.5 0100.0502.37e5.9f Infinite Manual
172.16.208.6 0100.e081.2e69.6a Infinite Manual
172.16.208.7 0100.0d60.11f4.89 Infinite Manual
172.16.208.8 0010.5aaa.8c7c Infinite Manual
172.16.208.9 0100.9027.3a4c.55 Infinite Manual
172.16.208.10 0100.0502.8e16.10 Infinite Manual
172.16.208.11 0100.6097.bbfe.e6 Infinite Manual
172.16.208.12 0010.4b21.5e02 Infinite Manual
172.16.208.13 0100.3018.a5ea.1a Infinite Manual
172.16.208.14 0100.1485.1e82.85 Infinite Manual
172.16.208.15 00d0.b7a9.26c2 Infinite Manual
172.16.208.58 0100.0475.99fe.e7 Infinite Manual
172.16.208.101 0050.04d7.c67c May 03 1993 12:26
PM Automatic
Post by Brad Stockdale
172.16.208.102 0100.c0b6.01b5.a3 May 03 1993 05:13
PM Automatic
Post by Brad Stockdale
172.16.208.129 00d0.b7a9.26c2 May 03 1993 08:06
PM Automatic
Post by Brad Stockdale
As you can see above, some of the Client-ID's have the 01 prepended,
and some do not... I cannot figure out why the router detects some of
then like that and others not. I know a Client-Identifier is partly a
microsoft invention, but even when I use the hardware-address
command, I cannot get dhclient to get the assigned address...
I was hoping that maybe someone out there has ran into this before
and can point me towards a solution or work-around.
Thanks in advance,
Brad
--
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David W. Hankins
2007-02-08 21:46:43 UTC
Permalink
Sorry I missed your original message.
Post by Brad Stockdale
172.16.208.15 00d0.b7a9.26c2 Infinite Manual
172.16.208.129 00d0.b7a9.26c2 May 03 1993 08:06 PM Automatic
ISC dhclient will 'remember' the most recent lease it had.

If dhclient had gotten this address from your Cisco before you assigned
the static, it will store a record of this in 'dhclient.leases' somewhere
on the client system (where depends on the system).

When it reboots, or is forcibly restarted, it will attempt to request
this address (using the requested-address option, #50).

So it may be that the Cisco is allowing the client to request an
address that is not statically configured for it (pretty reasonable
behaviour). Because the address is available, it lets the client
have it, even though it would give out a static normally.

That's my theory, anyway. ISC dhcpd does the same thing by default.

It's a good default.

In ISC dhcpd, we combat this "client stickiness" to leases by
providing explicit allow/deny syntax. In dhcpd.conf, you would
put "deny known;" or "deny members of classname;" in the relevant
dynamic pool, so that the client would not be offered leases from
the dynamic pool (it would be NAKed, and later OFFER'ed the fixed
address).

I don't know anything about Cisco DHCP config syntax, much less
enough to provide guidance on how to procede.

For dhclient's end, a simple fix would be to kill dhclient, remove
dhclient.leases, and start dhclient. It would accept whatever the
server OFFER'ed in that case then.
--
David W. Hankins "If you don't do it right the first time,
Software Engineer you'll just have to do it again."
Internet Systems Consortium, Inc. -- Jack T. Hankins
Andy Hood
2007-02-09 07:42:08 UTC
Permalink
Tim,
Post by Tim Philips
Client Ethernet Address: 00:0d:3a:4e:f4:da [|bootp]
The [|bootp] means your packets are truncated and all the interesting stuff
is missing.

You need to specify the snap length to tcpdump.

tcpdump -s 1500 -n -v -i eth0 udp port 67 or 68

Regards,
Andrew J Hood
Glenn Satchell
2007-02-09 12:34:46 UTC
Permalink
Date: Fri, 09 Feb 2007 21:18:22 +1300
Subject: Re: Clients not recieving IP's via DHCP
Hi Glenn (once again),
Thanks Andy for your advice on increasing the capture size. Below is a
21:10:56.334328 IP (tos 0x0, ttl 64, id 19400, offset 0, flags [none],
BOOTP/DHCP, Request from 00:0d:3a:4e:f4:da, length: 300, xid:0x889c873,
flags: [none]
Client Ethernet Address: 00:0d:3a:4e:f4:da
DHCP:DISCOVER
CID:[ether]00:0d:3a:4e:f4:da
VC:"XBOX 1.0"
PR:SM+DG+NS
RQ:192.168.0.4
21:10:56.441805 IP (tos 0x10, ttl 16, id 0, offset 0, flags [none],
BOOTP/DHCP, Reply, length: 300, xid:0x889c873, flags: [none]
Your IP: 192.168.2.252
Server IP: 192.168.2.1
Client Ethernet Address: 00:0d:3a:4e:f4:da
DHCP:OFFER
SID:127.0.0.1
LT:7200
SM:255.255.255.0
DG:192.168.2.1
NS:192.168.2.1
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