From: Semion Lisyansky (semionl@xxxxxxxxxxx)
Date: Thu May 17 2001 - 03:08:18 GMT-3
>From: "Pickell, Aaryn" <Aaryn.Pickell@getronics.com>
>Reply-To: "Pickell, Aaryn" <Aaryn.Pickell@getronics.com>
>To: "'Roman Rodichev'" <rodic000@hotmail.com>, ccielab@groupstudy.com
>Subject: RE: IRB
>Date: Thu, 17 May 2001 00:08:59 -0400
>
>The BVI interface just counts as another port on the bridge, though it
>doesn't show up on the show span output. So, things destined for MAC
>addresses located out physical interfaces will be forwarded there normally.
>Frames destined for the MAC address of the BVI will be sent there instead.
>Broadcasts will be sent to both, etc.
>
>I've seen cases where IP addresses on the physical interfaces would still
>work, and you could even route with them. But, they're not supposed to
>work.
When I've configured IRB on 2948/L3, BVI took MAC address of it's first
phisical interface, so it explains the above behavior.
>Per 'Configuring Transparent Bridging' from CCO
>(http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/ibm
>_c/bcprt1/bcdtb.htm#xtocid1869428):
>
>"When you intend to bridge and route a given protocol in the same bridge
>group, you must configure the network-layer attributes of the protocol on
>the bridge-group virtual interface. Do not configure protocol attributes on
>the bridged interfaces."
>
>Basically, all of the physical interfaces in the bridge-group represent a
>single Ethernet segment, right? That's the point of bridging... that
>you're
>simulating an ethernet with several smaller ethernets, to avoid contention
>issues, etc. So, imagine the BVI interface as being simply an ethernet
>interface on this meta-ethernet segment. Except that there is no physical
>plug on the router. To put layer 3 addresses on the physical interfaces
>sort of defeats the purpose of bridging in the first place.
>
>Aaryn Pickell - CCNP ATM, CCDP, MCSE
>Senior Engineer - Routing Protocols
>Getronics Inc.
>Direct: 713-394-1609
>Email:aaryn.pickell@getronics.com
>
>This e-mail message and any attachments are confidential and may be
>privileged. If you are not the intended recipient, please notify me
>immediately by replying to this message and please destroy all copies of
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>
>
> > -----Original Message-----
> > From: Roman Rodichev [mailto:rodic000@hotmail.com]
> > Sent: Wednesday, May 16, 2001 9:44 PM
> > To: ccielab@groupstudy.com
> > Subject: IRB
> >
> >
> > Quick question to everyone,
> >
> > when IRB is doing both bridging and routing for ip, what
> > takes precedence?
> >
> > let's say I got
> >
> > int e0
> > ip add 1.1.1.1 255.0.0.0
> > bridge-group 1
> > int bvi 1
> > (I'm not specifing IP Address here)
> > bridge irb
> > bridge 1 route ip
> > bridge 1 bridge ip
> >
> > I noticed that I can't ping 1.1.1.1 from another router,
> > unless I do "no
> > bridge 1 bridge ip"
> >
> > roman
> >
> >
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