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Old 06-30-2010, 09:41 AM   #1
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Question Can a bridge be configured to act as hub not a switch?


I have a hub with some VoIP phones attached as well as a machine that is used to record the calls. This all works fine as all packets coming to/from the voip phones are also seen by the recorder so it can process them as necessary.

What i want to do is put another machine between the hub and recorder and have it act as a transparent firewall. So far i've managed to successfully set up a bridge on ports eth1 and eth2 and all the packets destined for the recorder go through the bridge fine. The problem is that the bridge is acting as a switch so the packets from the phones are received on eth2 but don't get retransmitted on eth1. Is there any way to configure the bridge so that all packets received on eth2 are transmitted on eth1, i.e. have it act as a hub instead?
Old 06-30-2010, 10:16 AM   #2
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It can't be a firewall and a hub, any reason you can't use iptables on the monitor machine itself ? .. or use something like a cisco switch with monitor mode turned on to duplicate all traffic from the hubs port to the monitor machines port plus some outbound acl's ?

Old 06-30-2010, 10:32 AM   #3
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Typical, this has been bugging me for 2 days and within 20mins of posting i solve it! Thanks for the reply though.

The solution was to set the ageing of the bridge to 0 so it basically never has a list of learnt MAC addresses forcing it to transmit the packets regardless of whether the destination is connected via that port or not

brctl setageing 0 br0
Old 08-12-2014, 11:42 AM   #4
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This contradicts what the previous post says:

"Setting ageing time to zero makes all entries permanent."
Old 08-15-2014, 03:34 PM   #5
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All permanent entry is static, no dynamic entry anymore.


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