Dhcp Relay problem on 876

Unanswered Question
Sep 17th, 2007

Hi all,

I've configured an 876 (IOS: advipserv 12.4(6T)) as dhcp relay.

The 876 is connected to a backbone MPLS via ADSL and ISDN (backup to POP).

When the router works on ADSL...seems that the dhcp requests are not forwarded towards the DHCP server...On the contrary, on isdn line all works fine.

With a debug ip packet detail I can see the dhcp packet originated by the 'relay': ( is the dhcp server; is the ip lan of my router; Bvi1 is the wan interface bridged on Atm interface

Sep 17 16:40:54.046: IP: tableid=0, s= (local), d= (BVI1), routed via FIB

Sep 17 16:40:54.046: IP: s= (local), d= (BVI1), len 604, sending

Sep 17 16:40:54.046: UDP src=67, dst=67

but on the central site I can't see these packets.

My SP told me that any drop is done by the network.

If i try doing icmp request towards the dhcp server ( with source the IP Lan, all works fine..

I'm lost...

Any idea?

Many thanks in advance


I have this problem too.
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umedryk Fri, 09/21/2007 - 10:04

DHCP automatically assigns IP addresses to devices whenever you plug them in. For example, you can connect multiple Cisco IP Phones anywhere on the IP network and DHCP automatically assigns IP addresses to them. If DHCP is not enabled on a device, you must assign it an IP address.

Cisco IP Phones are DHCP-enabled by default. If you are not using DHCP, you need to disable DHCP on the phone and manually assign it an IP address.

DHCP is always enabled for Cisco Analog Access and Cisco Digital Access gateways.

For Cisco Catalyst 6000 8 Port Voice T1/E1 and Services Modules, the Network Management Processor (NMP) on the Catalyst 6000 may or may not have DHCP enabled. If DHCP is not enabled, you will need to configure the IP address through the Cisco IOS command-line interface on the Cisco Catalyst 6000


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