From: Pickell, Aaryn (Aaryn.Pickell@xxxxxxxxxxxxx)
Date: Thu May 17 2001 - 01:08:59 GMT-3
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. 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
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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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