topic Re: Linux bridge in Operating System - Linux

Linux bridge

Werner_14 — Sat, 17 May 2003 13:17:24 GMT

How correct configure bridge functionality
by using brcfg.
The "how to-Man" with description how to build up the bridge by activating kernel bridging capability and going the interfaces into promiscous doesn??t work in my configuration. Using kernel 2.4.15 SuSe Vers.8.0 and checking the same by Red Hat 7.2 give no sucess.
HW= 4 Network-Interfaces (dec, 2x 3com, olicom)
eth0 + eth1 have to be bridged. eth2 has the access to the internal sniffer LAN (No routing-
no firewall enabled)
eth3 has an direct IP-acess to corporate LAN (via DHCP)
I need a bridge to build up a sniffer-proxy.
Therefore the corporate LAN-station uses promiscous network-acess. The sniffing tools are located on to a pc using IPSec Features.

Re: Linux bridge

Nicolas Portais — Mon, 19 May 2003 11:57:01 GMT

Hi,

there is a HOWTo for Ethernet Bridge:
http://www.tldp.org/HOWTO/Ethernet-Bridge-netfilter-HOWTO.html

And about your error, are you verify that your linux kernel have the appropriate configuration:

"
Networking options:
[*] Network packet filtering (replaces ipchains)
[*] Network packet filtering debugging

IP: Netfilter Configuration --->:
802.1d Ethernet Bridging
[*] netfilter (firewalling) support
"

Regards,
Nicolas

Re: Linux bridge

Werner_14 — Sun, 01 Jun 2003 11:03:17 GMT

Hey dear Nicolas Portais,
first of all thank you for the hint and your answer.
The problem was??nt solved. The reason is I have to use brcfg without any participating netfilter (IPtaples) options.
Give me a hint, if you have experiences using the PC as an bridging device, using to eth-interfaces (real eth0 an eth1 - different products - 3com an olicom) in promiscous mode, without any protocol.
the common orders are
ifconfig eth0 promisc and
ifconfig eth1 promisc
brcfg ena
the bridge reacts only with arp data-streams.
the kernel options bridging enable 802.1 was set.
If you have an idea please contact me.

thanks herbert

Re: Linux bridge

Nicolas Portais — Mon, 02 Jun 2003 07:46:15 GMT

Hi,

Personally, I don't have a experience with bridging but an ethernet bridge works as a router: connect two networks.

try these commands:

$ brctl addbr br0
$ brctl stp br0 off
$ brctl addif br0 eth0
$ brctl addif br0 eth1
$ ifconfig eth0 down
$ ifconfig eth1 down
$ ifconfig eth0 0.0.0.0 up
$ ifconfig eth1 0.0.0.0 up
$ echo "1" > /proc/sys/net/ipv4/ip_forward

do you have errors ? do you ping a host through the bridge ?

but to set up a proxy, the another solution is to use squid and iptables (forwarding port 80 to 8080).

Regards,
Nicolas