DHCP / Manually assigned ip issue

Unanswered Question
Jul 23rd, 2010
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I am actually having an issue with manually assigned IP addresses by a DHCP server on a Cisco 2621XM (12.3.25).

We are actually using a central UNIX DHCP server without any problem since a few years but, for IP Telephony (a Nortel IP phone long story) purposes, I had to move the DHCP server hosting the branch segment to the local router. We actually provide random DHCP addresses to pc's and phones but, we always assign static adresses to printers. It seem that Cisco DHCP has some issue in those cases and, I just wan't an "official confirmation" so I'll stop searching for the solution.

So, here is the situation on a technical point of view.

This is the MAC I see on the printer switch port ..

Vlan    Mac Address       Type        Ports
----    -----------       --------    -----
  49    0014.38dc.324a    STATIC      Fa0/1

.. and my DHCP server config ..

! ------MAIN POOL------

ip dhcp pool FLAT-DRM
   option 128 ascii "Nortel-i2004-A,,1,5."
   option 191 ascii "VLAN-A:12."
   lease 3


! ----- STATIC POOL -----

ip dhcp pool IPDRM0002
   client-identifier 0100.1438.dc32.4a (or with hardware-address 0014.38dc.324a)
   client-name IPDRM0002
   lease infinite

It seem that this configuration (with client-identifier) work's fine with a few printers but, I remark that most of them have all different ways to do the DHCPDiscover process. Here what I am getting in the debug for this specific printer ..

Jul 23 09:35:55: DHCPD: DHCPDISCOVER received from client 0000.1438.dc32.4a on interface FastEthernet0/0.49.
Jul 23 09:35:57: DHCPD: Sending DHCPOFFER to client 0000.1438.dc32.4a (
Jul 23 09:35:57: DHCPD: creating ARP entry (, 0014.38dc.324a).
Jul 23 09:35:57: DHCPD: unicasting BOOTREPLY to client 0014.38dc.324a (
Jul 23 09:35:57: DHCPD: DHCPREQUEST received from client 0000.1438.dc32.4a.
Jul 23 09:35:57: DHCPD: Sending DHCPACK to client 0000.1438.dc32.4a (
Jul 23 09:35:57: DHCPD: creating ARP entry (, 0014.38dc.324a).
Jul 23 09:35:57: DHCPD: unicasting BOOTREPLY to client 0014.38dc.324a (

It seem that some devices send a media-type before the mac-address and some don't. Also, they can put 01 as ethernet media-type and 00 (for this specific case) wich is ... no idea ...

I searched on many forums and, found this thread where someguy have the exact same issue than me.


Here's the easiest way to do your manual bindings.

1. on your DHCP server, turn on:


ip dhcp server events
debug ip dhcp server packet

2. reboot your printer and watch its DHCP (or possibly BOOTP)
request come in

3. issue the command "show ip dhcp binding"

If the printer got the manual binding, then that's great.
If it got an address from the pool instead, then use
its client ID / hardware address instead.

Note: if "show ip dhcp binding" shows the "hardware address"
in MAC address format, a la 0001.e667.92ad, then use that
as hardware-address rather than as client-identifier. If
binding shows some other format, then that's a

Our documentation on this could use some work I'm afraid.



The DHCP reply to the client using the media-type and, create a APR entry without it but, why do I need to debug just to be able to assign an IP address. Unix just don't care about the media-type and, assign the address using the MAC address only.

host ipdrm0002      { hardware ethernet 00:14:38:dc:32:4a; fixed-address; }

Is the DHCP service better on a more recent IOS?

Thank for your help or comments.

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