From: StudyManiac (groupstudy1@xxxxxxxx)
Date: Wed Feb 13 2002 - 17:27:32 GMT-3
The BVI represents a group of bridged interfaces to the rest of the routed
interfaces. In other words, bridged interfaces stop at layer 2, and the BVI
adds the layer 3 component to those bridged interfaces. Think of it as a
switch with a layer 3 module: the bridged interfaces on the router are like
ports on a switch. The BVI is like the vlan interface on the layer 3
module. Of course, if you haven't worked on a layer 3 switch this is only
more confusing, so ignore the last two sentences in that case.
Back to the router: If you put interfaces in a bridge group and also
configure an IP address on the bridged interfaces, you must not plan to
bridge IP ('cause bridging is layer 2, ip addresses are layer 3), so you
don't need one on the BVI. If you do NOT have IP addresses on the bridged
interfaces, then you will bridge IP traffic, (but only if you disable
routing for that bridge group), since there is no layer three information
for which to route traffic to/from. Got it? IRB is one of the more
confusing things about Cisco's bridging/routing strategy, but once you get
it down, it makes sense.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Williams, Glenn
Sent: Wednesday, February 13, 2002 12:10 PM
To: 'ccielab@groupstudy.com'
Subject: IRB
Can someone tell me when I do and do not need an ip address on the BVI
interface when doing IRB.
TIA
GW
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