From: Kirk Graham (kgraham@instructors.net)
Date: Mon Nov 22 2004 - 13:52:44 GMT-3
Sounds like a bug in that IOS release to me.
I just tried it on my 12.2(10b) and it works fine. I blew out the config
and rebuilt it. Still works.
I did a quick search on the Cisco Bug Tracker and there are several "minor"
bug notices about OSPF and summaries, but I didn't see anything Null0
specific with the area range statement.
As far as I can remember installing a Null0 route matching the OSPF area
summary is a recent addition to the IOS. EIGRP had done it for a while, but
I think OSPF just got that sometime in the 12.x code. Probably still buggy.
How long did you wait? Sometimes it take a few seconds for the summary to
start being advertised. By then, the Null0 route should appear. But it
won't be instantaneous.
--kg
At 10:23 AM 11/22/2004, gladston@br.ibm.com wrote:
>This problem came when studying Doyle I, on the OSPF chapter that says we
>should add a route to null when performing IA summarization. I thought it
>had changed on new versions but the result I am getting is confusing.
>Sometimes the IOS adds automatically, sometimes it does not.
>
>Any similar experience? The IOS is 12.2(1d).
>
>r2#sir
> 172.16.0.0/16 is variably subnetted, 10 subnets, 3 masks
>O 172.16.6.128/27 [110/11] via 172.16.26.6, 00:27:58, Ethernet0
>O 172.16.6.32/27 [110/11] via 172.16.26.6, 00:27:58, Ethernet0
>C 172.16.25.5/32 is directly connected, Serial1
>C 172.16.25.0/24 is directly connected, Serial1
>C 172.16.26.0/24 is directly connected, Ethernet0
>C 172.16.23.0/24 is directly connected, Serial0.23
>O 172.16.6.0/24 is a summary, 00:27:59, Null0
>O 172.16.6.0/27 [110/11] via 172.16.26.6, 00:28:00, Ethernet0
>C 172.16.2.0/24 is directly connected, Loopback0
>O 172.16.6.64/27 [110/11] via 172.16.26.6, 00:28:00, Ethernet0
>r2#
>
>After no router ospf1, and configuring it again:
>
>r2#sir os
> 172.16.0.0/16 is variably subnetted, 10 subnets, 4 masks
>O 172.16.6.128/27 [110/11] via 172.16.26.6, 00:09:16, Ethernet0
>O 172.16.6.32/27 [110/11] via 172.16.26.6, 00:09:16, Ethernet0
>C 172.16.25.5/32 is directly connected, Serial1
>C 172.16.25.0/24 is directly connected, Serial1
>C 172.16.26.0/24 is directly connected, Ethernet0
>C 172.16.23.0/24 is directly connected, Serial0.23
>O 172.16.6.0/27 [110/11] via 172.16.26.6, 00:09:16, Ethernet0
>C 172.16.2.0/24 is directly connected, Loopback0
>O 172.16.6.64/27 [110/11] via 172.16.26.6, 00:09:17, Ethernet0
>
>I tried to find any other point that could cause this behavior, with no
>success. The configuration is the same on both cases.
>
>This is the configuration:
>
>router ospf 1
> log-adjacency-changes
> area 1 range 172.16.6.0 255.255.255.0
> network 172.16.25.0 0.0.0.255 area 0
> network 172.16.26.0 0.0.0.255 area 1
>
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