Bridge Group question... "Encapsulation Failed" on a BVI...

I am working on something in the lab, and I was wondering...

I have two HDLC serial connections that I am bridging together...

bridge irb ! interface Serial0 no ip address clockrate 56000 bridge-group 1 ! interface Serial1 no ip address clockrate 56000 bridge-group 1 ! interface BVI1 ip address 10.254.39.227 255.255.255.248 ! bridge 1 protocol ieee bridge 1 bridge ip < - this command has been entered but doesn't show up in the config

The other two routers are at .225 and .226

When I ping from 226 to 227, I get:

00:35:38: IP: tableid=0, s=10.254.39.227 (local), d=10.254.39.226 (BVI1), routed via RIB 00:35:38: IP: s=10.254.39.227 (local), d=10.254.39.226 (BVI1), len 100, sending 00:35:38: IP: s=10.254.39.227 (local), d=10.254.39.226 (BVI1), len 100, encapsulation failed

Why?

Jonathan

Hi Jonathan,

Bridging is Layer 2, IP is Layer 3. So you have no path for Layer 3 between the devices, thats why your encapsulation failed. It goes back to near the beginning of your post -

Thats because a Bridge group only Bridges by default. You are probably thinking of -

^^^^^^^^ Meaning all data EXCEPT IP would be bridged on that link. So your problem is that IP addressing is irrelevant at the frame (bridge) level and routing of IP addressing does not exist.

A BVI allows you to attach Layer 3 properties to a Layer 2 entity and nothing more. You still need to tell the Router what to do with Layer

3 traffic on that interface (otherwise why are you adding IP addressing to it)?.

Consider this as an example that may help - I had one site that had a Router connecting the local Ethernet segment to a 512Kb/s Frame-Relay WAN link. They needed MAC filtering to be applied, however because a Router Ethernet interface normally operates in Layer 3 mode, a MAC ACL is not valid. If I BRIDGED the Ethernet to the WAN link, then effectively the LAN would be slowed from 10Mb to the speed of the Frame-Relay WAN (512Kb/s), so I converted the Ethernet to Bridged mode, Bridged it to a BVI, meaning the Ethernet was in Layer 2 mode, ran at Ethernet speed, and so could take the MAC ACL, and the BVI allowed me to ROUTE off that interface, meaning the Ethernet was not restricted by the WAN link speed.

Cheers...............pk.