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= Bridge doesn't forward packets = Sometimes a bridge can mysteriously drop the packets and not forward them.e.g. eyck user experienced a problem when some of the broadcasts were not delivered to VE container via the bridge.
VE Container #101 with veth interface (veth101.0) connected to eth0 physical interface via bridge.
→Another Problem Case
Original report and the thread: [http://forum.openvz.org/index.php?t=tree&th=4052& forum thread]
== Simplest configuration ==
== Problem statement ==
We faced a situation when some of the broadcast packets were not delivered to the VEcontainer.Actually it could happen with any packets, not with the broadcasts only. But broadcasts aresimpler and obviously should have been delivered to all the networking interfaces with no doubt.
Using tcpdump we see that BOOTP/DHCP request is visible on br0 interface in the host system (VE0[[CT0]]):
15:21:52.258220 00:1b:d5:2c:bf:38 > ff:ff:ff:ff:ff:ff, ethertype IPv4 (0x0800), length 350: 0.0.0.0.68 > 255.255.255.255.67:
BOOTP/DHCP, Request from 00:1b:d5:2c:bf:38, length 308
BOOTP/DHCP, Reply, length 300
However, eth0 inside VE receives the container received only 2nd packet with a BOOTP/DHCP reply and doesn't see the 1st one with the request itself:
15:21:52.291145 00:08:02:ac:36:20 > ff:ff:ff:ff:ff:ff, ethertype IPv4 (0x0800), length 342: 172.17.8.254.67 > 255.255.255.255.68:
BOOTP/DHCP, Reply, length 300
== Resolution ==
It is not obvious at all, but bridges (though they have their own ebtables filters) do also call iptables FORWARD chain when forwarding packets between interfaces.
Thus your FORWARD iptables rules should allow all the packets which are supposed to go through.
iptables -A FORWARD -d 255.255.255.255 -j ACCEPT
to fix the issue.
== Another Problem Case ==
I had setup a bridge and got the same problem, but iptables was setup well. In my case the problem was lying in /proc/sys/net/bridge/.
Everything inside had value "1". Changing them to "0" solved the problem. This stopped ARP and bridge packets from being
passed through the FORWARD chain. These settings can be placed inside /etc/sysctl.conf (Debian) so that they are persistent.
== Credits ==