From: Scott Morris (smorris@ipexpert.com)
Date: Mon Nov 05 2007 - 14:48:45 ART
Remember that your virtual link IS an area 0 interface. So when you extend
area 0, you are kinda bypassing some of the summarization you may have done
in normal area to area operations.
HTH,
Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIE-M
#153, JNCIS-ER, CISSP, et al.
CCSI/JNCI-M/JNCI-ER
VP - Technical Training - IPexpert, Inc.
IPexpert Sr. Technical Instructor
A Cisco Learning Partner - We Accept Learning Credits!
smorris@ipexpert.com
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http://www.ipexpert.com
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Joseph Brunner
Sent: Monday, November 05, 2007 11:10 AM
To: 'groupstudy'
Subject: area 0 range & virtual links
I would like to bring to your attention an interesting issue I ran into this
morning. When summarizing area 0 routes (in this case /32's from a p2mp area
0 frame relay cloud) virtual links broke the summary, and continued to allow
the /32 lsa's out, instead of just the /24 summary.
Here is an area 0 router's ospf config
rack1r2#sh run | b router ospf
router ospf 1
router-id 1.1.2.2
log-adjacency-changes
area 0 authentication message-digest
area 0 range 1.1.20.0 255.255.255.0
area 422 virtual-link 1.1.8.8 authentication message-digest
area 422 virtual-link 1.1.8.8 message-digest-key 1 md5 cisco
network 1.1.2.2 0.0.0.0 area 0
network 1.1.20.2 0.0.0.0 area 0
network 1.1.22.2 0.0.0.0 area 422
My areas are 0, 422, 331 with 211 being isolated from the backbone. Sw1 and
sw2 are in ABR's between 331/211 and 422/211 respectively and the virtual
link destinations from the "area 0" backbone routers". Between the two
switches is R1, an internal area 211 router.
It took putting the "area 0 range 1.1.20.0 255.255.255.0" on sw1 and sw2
(the ends of the virtual links) to get Router 1 to ONLY see the /24 summary
route.
(before)
rack1r1#sh ip route 1.1.20.3
Routing entry for 1.1.20.3/32
Known via "ospf 1", distance 110, metric 1796, type inter area
Last update from 1.1.21.2 on FastEthernet0/1, 00:00:36 ago
Routing Descriptor Blocks:
* 1.1.21.2, from 1.1.8.8, 00:00:36 ago, via FastEthernet0/1
Route metric is 1796, traffic share count is 1
(after)
rack1r1#sh ip route 1.1.20.3
Routing entry for 1.1.20.0/24
Known via "ospf 1", distance 110, metric 2, type inter area
Last update from 1.1.21.2 on FastEthernet0/1, 00:00:04 ago
Routing Descriptor Blocks:
* 1.1.21.2, from 1.1.8.8, 00:00:04 ago, via FastEthernet0/1
Route metric is 2, traffic share count is 1
i.e. here is sw1's config
rack1sw1#sh run | b router ospf 1
router ospf 1
router-id 1.1.7.7
log-adjacency-changes
area 0 range 1.1.20.0 255.255.255.0
area 331 virtual-link 1.1.3.3 authentication message-digest
area 331 virtual-link 1.1.3.3 message-digest-key 1 md5 cisco
redistribute eigrp 10 subnets tag 188
network 1.1.7.7 0.0.0.0 area 211
network 1.1.11.11 0.0.0.0 area 211
network 1.1.13.1 0.0.0.0 area 331
Anyone care to comment on this behavior. I was previously unaware virtual
links endpoints required area range commands for area 0 lsa's we are
summarizing.
-Joe
This archive was generated by hypermail 2.1.4 : Sat Dec 01 2007 - 06:37:28 ART