From: Scott Vermillion (scott_ccie_list@it-ag.com)
Date: Mon Nov 05 2007 - 13:53:45 ART
Joe,
It's possible I'm missing a nuance or two here. But it seems normal to me.
The virtual links are nothing but tunnels for OSPF (not payload according to
my recent research) traffic. Thus, logically, the Virtual links simply
"move" SW1 and SW2 to the backbone. In that regard, they are everyday ABRs
for Area 211. They will be getting the same backbone LSAs as routers
physically attached to the backbone and will be implementing the same ABR
logic and behavior. They do not somehow become subordinate to their virtual
link endpoints that are actually attached to the backbone (i.e. they will
not be receiving the LSAs that summarize routes into Areas 331 or 422, as
those LSAs belong to and are originated into areas separate from 211).
"Have I ever mentioned how much I hate Virtual Links?"
Regards,
Scott
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Joseph Brunner
Sent: Monday, November 05, 2007 9:10 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