I'm trying to get bridging to work with a RedHat 8.0 system (kernel
2.4.18-19.8.0) and I'm not having much success.

I have a Linux Firewall (RH 8.0) connected to an Adelphia cable modem on
eth0 and my home network hub on eth1.  The bridge machine and 4 Windows
machines are connected to the hub.

I reconfigured as follows:

Remove the firewall eth1 connection to the hub and connect it with a
crossover cable to eth0 on the bridge machine.  The eth1 interface on the
bridge machine remains connected to the hub.

I'm attempting a simple experiment first so I've set my Netfilter rules as
follows:

iptables --policy INPUT   ACCEPT
iptables --policy OUTPUT  ACCEPT
iptables --policy FORWARD ACCEPT

iptables -t nat --policy PREROUTING  ACCEPT
iptables -t nat --policy OUTPUT      ACCEPT
iptables -t nat --policy POSTROUTING ACCEPT

iptables -t mangle --policy PREROUTING  ACCEPT
iptables -t mangle --policy OUTPUT      ACCEPT

# Remove any existing rules from the built-in chains
iptables --flush
iptables -t nat --flush
iptables -t mangle --flush

# Remove any pre-existing user-defined chains
iptables --delete-chain
iptables -t nat --delete-chain
iptables -t mangle --delete-chain

I configure the bridge as follows:

ifconfig eth0 down
ifconfig eth1 down
ifconfig eth0 0.0.0.0 promisc
ifconfig eth1 0.0.0.0 promisc
brctl addbr br0
brctl stp br0 off
brctl addif br0 eth0
brctl addif br0 eth1
ifconfig br0 192.168.0.2 up
route add default gw 192.168.0.100

"brctl showmacs br0" shows the ethernet addresses of all machines as
expected and using gbrctl the ethernet interfaces go from listening to
learning to forwarding as expected.

None of the Windows machines can see the firewall with the bridge enabled.
Ethereal shows
packets being on eth0 but no responses from either the bridge machine or the
firewall.

/var/log/messages contains:

Jan 12 15:45:44 Polo-Morgan kernel: ip_conntrack (512 buckets, 4096 max)
Jan 12 15:47:30 Polo-Morgan kernel: NET4: Ethernet Bridge 008 for NET4.0
Jan 12 15:47:31 Polo-Morgan kernel: device eth0 entered promiscuous mode
Jan 12 15:47:31 Polo-Morgan /etc/hotplug/net.agent: invoke ifup br0
Jan 12 15:47:31 Polo-Morgan kernel: device eth1 entered promiscuous mode
Jan 12 15:47:31 Polo-Morgan kernel: eth0: Setting promiscuous mode.
Jan 12 15:47:31 Polo-Morgan last message repeated 4 times
Jan 12 15:47:31 Polo-Morgan kernel: eth1: Promiscuous mode enabled.
Jan 12 15:47:31 Polo-Morgan last message repeated 3 times
Jan 12 15:47:31 Polo-Morgan kernel: br0: port 2(eth1) entering listening
state
Jan 12 15:47:31 Polo-Morgan kernel: br0: port 1(eth0) entering listening
state
Jan 12 15:47:46 Polo-Morgan kernel: br0: port 2(eth1) entering learning
state
Jan 12 15:47:46 Polo-Morgan kernel: br0: port 1(eth0) entering learning
state
Jan 12 15:48:01 Polo-Morgan kernel: br0: port 2(eth1) entering forwarding
state
Jan 12 15:48:01 Polo-Morgan kernel: br0: topology change detected,
propagating
Jan 12 15:48:01 Polo-Morgan kernel: br0: port 1(eth0) entering forwarding
state
Jan 12 15:48:01 Polo-Morgan kernel: br0: topology change detected,
propagating
Jan 12 15:50:20 Polo-Morgan kernel: eth0: Setting promiscuous mode.
Jan 12 15:54:52 Polo-Morgan ntpd[657]: synchronisation lost
Jan 12 16:05:47 Polo-Morgan kernel: br0: port 2(eth1) entering disabled
state
Jan 12 16:05:47 Polo-Morgan kernel: br0: port 1(eth0) entering disabled
state
Jan 12 16:05:48 Polo-Morgan kernel: br0: port 1(eth0) entering disabled
state
Jan 12 16:05:48 Polo-Morgan kernel: br0: port 2(eth1) entering disabled
state

It looks like it should be working but I've probably overlooked something
stupid.  Can someone enlighten me?

Thanks,

Brad Morgan


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