From: Geert Nijs (Geert.Nijs@simac.be)
Date: Fri May 09 2008 - 12:01:14 ART
Hi group,
I was wondering how an OSPF router would react in the following case.
Suppose you have an ABR router between area 0 and area 1100 (stub no-summary area).
This router generates a default route into area 1100 as an intra-area route.
Suppose this router also receives a default route from area 0 as an External route (LSA 5).
What will be put in the routing table of this ABR ? The OSPF database would look like:
Summary Net Link States (Area 1100)
Link ID ADV Router Age Seq# Checksum
0.0.0.0 10.216.157.1 1334 0x80006654 0x0061A1
0.0.0.0 10.216.157.2 1336 0x800074D3 0x003242
Type-5 AS External Link States
Link ID ADV Router Age Seq# Checksum Tag
0.0.0.0 192.168.1.32 1238 0x80012829 0x0057F8 1
0.0.0.0 192.168.1.43 1513 0x80008D14 0x0013E2 1
The router should put the external in its routing table (and probably will), but
doesn't a summary (intra-area) take precedence over an external link (inter-area) ?
Or will the router see that the summary intra-area route is generated by itself
and therefore not put it in the routing table (avoiding blackholing) ?
What if there is a redundant router present also advertising this default, maybe
it will except this one over the external ones ?
regards,
Geert
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