Two discontinuous OSPF backbones

From: jellyboy (jellyboy@gmail.com)
Date: Fri Jan 28 2005 - 16:01:52 GMT-3


Hi all,

Got a scenario where two discontinuous ospf backbone areas are joined
by area 15.

Area0<R5>Area15<R1>Area0

Normally I would configure a virtual-link between the two Area0s.
However the problem states that the virtual-link command can not be
used. Their solution was to have two ospf processes running on R1 and
redistribute between them.

router ospf 1
 log-adjacency-changes
 redistribute ospf 15 subnets
 network 172.16.124.0 0.0.0.7 area 0
 network 192.168.1.1 0.0.0.0 area 0
!
router ospf 15
 log-adjacency-changes
 redistribute ospf 1 subnets
 network 172.16.15.0 0.0.0.15 area 15

This solution works, but only if two backbone areas are bounded by
another area, area 15 in this case.

My questions are :
1) Does this mutual redistribute solution only work between
discontinuous backbone areas??
Reason is I tried this by replacing the R5 area 0 by an area 1:

Area1<R5>Area15<R1>Area0

This gave the dreaded:

01:05:31: %OSPF-4-ERRRCV: Received invalid packet: mismatch area ID, from backbo
ne area must be virtual-link but not found from 172.16.136.3, Ethernet0

So I guess it does not work but I would like confirmatiom, comments etc.

2) Are there any other solutions lurking out there for this type of
topology that I should be make aware of?

TIA

jellyboy



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