dhcpd and IPIP tunnels.

Kelvin Williams kelvin-lists at geniusnetworks.net
Thu Mar 23 16:41:42 UTC 2006

I have been reading the archives and have seen that others have encountered
this problem yet I have not found a solution.  

We have an established tunnel between a Cisco router and a Linux box.  
Cisco Interface Tunnel0 ( <=> Linux tunnel0 (

Behind the Cisco router we have a CMTS (cable modem termination system) with
the "ip helper-address" set to for all DHCP requests.  We have
verified connectivity between the CMTS and the Tunnel0 interface on the
Linux box.  We have additionally verified that the requests are surviving
their journey through the tunnel using tethereal.  

However when we run dhcpd with the -f -d flags, and point it to the tunnel0
interface we get:

[root at sandbox ~]# /usr/sbin/dhcpd -f -d tunnel0
Internet Systems Consortium DHCP Server V3.0.3
Copyright 2004-2005 Internet Systems Consortium.
All rights reserved.
For info, please visit http://www.isc.org/sw/dhcp/
Wrote 0 deleted host decls to leases file.
Wrote 0 new dynamic host decls to leases file.
Wrote 0 leases to leases file.
Listening on LPF/tunnel0//
Sending on   LPF/tunnel0//
Sending on   Socket/fallback/fallback-net

Is it not possible for the dhcpd to listen to the tunnel interface?

Thanks in advance.

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