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Old 11-22-2003, 01:18 PM   #1
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Registered: Jul 2003
Location: Texas
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Passing DHCP over a transparent bridge

Okay, I've run into a problem here and I cant seem to find anything at all out there specific to this, I'm running a router w/ a dhcp server on it, and I'm attempting to insert a transparent bridge in between the network and the router to do firewalling/content filtering. I've got everything working put this one specific thing, I cannot for the life of me figure out how to pass dhcp traffic over this bridge, not entirely at least, the initial request response goes over just fine, but getting the acknowledge back is just not working in any mode whatsoever, I've tried ISC's dhc-relay, I've got ebtables on the machine, none of the rulesets I tried there worked, nothing in netfilter/iptables has worked, so I'm wondering if anyone out there has any ideas or has gotten this successfully implemented.

System Specifics:
Kernel 2.4.20 w/ bridge-nf-bds 0.0.10, ebtables 2.0.03 and ptrace patches
iptables 1.2.7a
iproute2 2.4.7
ebtables userspace tools 2.0.5
bridge-utils 0.9.6
Old 11-23-2003, 02:33 PM   #2
Registered: Mar 2003
Distribution: Slackware
Posts: 234

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run tcpdump on the other side of your bridge, see if you can see a dhcp server response come back across the bridge. Run tcpdump on the dhcp server side of the bridge, see if you see the request hitting your side. Then you can pinpoint where it's failing and how to resolve it.

Hope this helps.
Old 11-24-2003, 10:17 PM   #3
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got it..

Had already done that the response was getting through, just not back across the bridge, finally got it early this morning
Solution was to setup netfilter/iptables to allow traffic over udp 67/68, coupled with running dhc-relay on the bridge interface(br0), had only tried dhc-relay on the individual interfaces themselves instead of letting it run on the bridge interface


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