Hello. I'm trying to get an ethernet bridge running, and after
following the simple instructions in the FAQ I'm stuck.
My test bridge machine has three network cards:
- eth0 is the "normal" interface, a SIS900 on the motherboard, and has
an IP address (10.134.1.188) assigned by DHCP. Everything works fine
with that.
- eth1 and eth2 are both intel eepro100 cards, untouched by the system
startup scripts.
The network config is: I have a small 10/100 switch on my desk with an
uplink to the company router. Both eth0 and eth1 are attached to the
switch. eth2 is attached to a single machine I'll call "client".
|--------| |-----------------------| |--------|
| switch |<------->|eth0 bridge machine | | client |
| |<------->|eth1<------------->eth2|<-->|--------|
|--------| |---------------------- |
The goal is to have my bridge machine do all it's own network
communication through eth0, and have an eth1<-->eth2 bridge which allows
the client to see the network. (Later on I plan to add filtering to
this bridge, but for now it's just a stock 2.4.19-pre2 kernel without
any filtering or firewalling options.)
I don't want the bridge machine to do any of it's own communication
using the bridge. This is important: the bridge interfaces must be used
ONLY for bridging. If the bridge machine wants to talk to the client,
it should communicate out eth0 to the switch.
So, to begin with the bridge machine is working fine. The startup
scripts configured eth0 as 10.134.1.188, it is running, and the eth1 and
eth2 cards for the bridge don't even have drivers loaded.
Then, as root I do this:
# modprobe eepro100
(driver finds both cards, and ifconfig -a now shows eth1 and eth2)
# brctl addbr br0
(ifconfig -a now also shows br0)
# brctl addif br0 eth1
# brctl addif br0 eth2
dmesg shows both cards entering promiscuous mode, and "brctl show"
indicates:
bridge name bridge id STP enabled interfaces
br0 8000.0002b3102680 yes eth1
eth2
So I try to bring up the bridge by assigning it an unused IP
address on the subnet (I still don't understand why this is
necessary, by the way, but that's what the instructions say):
# ifconfig br0 10.134.1.2
Now, I see:
# ifconfig -a
br0 Link encap:Ethernet HWaddr 00:02:B3:10:26:80
inet addr:10.134.1.2 Bcast:10.255.255.255 Mask:255.0.0.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
[ as well as eth0, eth1, eth2, and lo. Everything looks correct,
eth1 and eth2 do not have IP addresses of their own.]
So everything looks right, I think. The problems are:
1. "route -n" on the bridge machine shows that the bridge has been
added to the routing table:
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
10.134.0.0 0.0.0.0 255.255.254.0 U 0 0 0 eth0
10.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 br0
127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 lo
0.0.0.0 10.134.0.1 0.0.0.0 UG 0 0 0 eth0
I don't want that. In fact, the bridge machine can't communicate
over the net anymore, it seems to have quit using eth0. If I try
to delete that route, "route del 10.0.0.0" I get
SIOCDELRT: No such process
2. Packets are not forwarded.
When the client machine on the eth2 side of the eth1--eth2 bridge tries
to DHCP, with the DHCP server on the eth1 side of the bridge, nothing
crosses the bridge.
"tcpdump -i br0" only shows arp from the bridge machine trying to find
the nameserver (10.128.0.50):
"16:15:31.970200 arp who-has 10.128.0.50 tell 10.134.1.2"
but no other packet traffic...
"ifconfig -a" shows the TX and RX counts on eth1 and eth2 stay at zero,
while the TX count on br0 seems to just show the arp packets going out.
Any hints on how to make this work? I'm stuck.
Thanks...
Torrey Hoffman
[EMAIL PROTECTED]
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