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List:       ipfilter
Subject:    Re: Transparent Bridge with 3 nics.
From:       Jim Sandoz <sandoz () lucent ! com>
Date:       2001-07-26 2:58:02
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maikel,

you will need to use an OS and version that supports the spanning-tree
bridge protocol-- else you are facing and will continue to face the
classical looped ethernet network problem.

according to
http://www.openbsd.org/29.html
openbsd 2.9 now supports spanning tree, see
http://www.openbsd.org/cgi-bin/man.cgi?query=bridge&sektion=4

for more info on spanning tree itself, see for example
http://www.cisco.com/warp/public/473/5.html
http://www.cisco.com/warp/public/473/16.html

and the product/catos/ios-specific info at
http://www.cisco.com/univercd/cc/td/doc/product/lan/cat5000/rel_5_2/config/spantree.htm

http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/12cgcr/ibm_c/bcprt1/bctb.htm

you may be interested in the mechanics of cisco's "portfast" function.

the foundation of spanning tree is found in IEEE 802.1D-1998.

n.b.
be sure that your ipf rules on the bridge can pass the BPDU's.

jim

ps
the "other" question is-- why does the first bridge break? and if
you want you can save time booting the second machine by just
unplugging the CAT5 cables at the network interfaces... :*)

pps
according to
http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/bridging.html
http://www.FreeBSD.org/cgi/man.cgi?query=bridge&sektion=4
freebsd does not have native support for spanning tree.
there may be some patches or packages which do so.
the default on freebsd is that the interface is muted upon
detection of a loop.  see
http://www.FreeBSD.org/cgi/man.cgi?query=ng_bridge&sektion=4&apropos=0&manpath=FreeBSD+4.3-RELEASE







Maikel Verheijen wrote:

> Hi all,
>
> Regarding to this question, I have another one concerning a bridge:
>
> I want to create a fail-over situation by using two identical filtering
> (openbsd) bridges like this:
>
> +---------------------------------------------------------------------+
> |                  Internet (Attached through cisco catalyst, vlan 1) |
> +---------------------------------------------------------------------+
>              |                                           |
>         +---------+    B-1: Bridge 1                +---------+
>         |   B-1   |    B-2: Bridge 2                |   B-2   |
>         +---------+                                 +---------+
>              |                                           |
> +---------------------------------------------------------------------+
> |                  LAN (Attached to Cisco catalyst, vlan 2)           |
> +---------------------------------------------------------------------+
>
> However, this situation gives me a headache, because whenever both bridges
> are enabled, the complete network gets cluttered by a broadcast storm. I am
> not familiar enough with openbsd and bridging to sort this out, so I hope
> someone on the list can help me out here.... I would REALLY like to get
> this thing up and running smoothly,  booting the second machine whenever
> the first machine breaks takes too long :(
>
> Thanks in advance,
>
> Maikel Verheijen.

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