[c-nsp] Limiting DHCP on a Bridge Group

Garry gkg at gmx.de
Wed Feb 10 12:50:09 EST 2010


I've got a setup that could use some tweaking ...

CPE is a 876W, with the 4 wired switch ports (read: VLAN1) and the WLAN
being in a bridge group, LAN ip on the BVI1 interface.

LAN ports are only for designated boxes, while there are select users
that may use the WLAN link to connect. For those, the router is running
as a DHCP server, too.
Anyway, I would like to limit the DHCP answers to just the WLAN link. I
know I could go ahead and just split up the bridge group, with routing
between the networks, but due to some other requirements, WLAN and wired
lan needs to be in the same broadcast domain (at least unless the
customer goes through some major reconfiguration).

I've received some suggestion as to using a policy map with class maps
matching on proto dhcp and the incoming interfaces, dropping the traffic
when it matched, while still forwarding the class default ... anyway, I
tried setting that up, but still got DHCP on the FE ports ...

Any other suggestions? Or some hint on what I missed? Here's an excerpt
from the config ...

class-map match-all NODHCP
 match protocol dhcp
 match input-interface FastEthernet0
class-map match-all NODHCP1
 match protocol dhcp
 match input-interface FastEthernet1
class-map match-all NODHCP2
 match protocol dhcp
 match input-interface FastEthernet2
class-map match-all NODHCP3
 match protocol dhcp
 match input-interface FastEthernet3

policy-map NODHCP
 class NODHCP
 class NODHCP1
 class NODHCP2
 class NODHCP3
 class class-default
interface BVI1
 ip address
 service-policy input NODHCP

Help appreciated, -garry

More information about the cisco-nsp mailing list