From: marvin greenlee (marvin@ccbootcamp.com)
Date: Fri Mar 04 2005 - 17:30:13 GMT-3
Virtual links are extensions of Area 0.
Virtual links have area border routers as their endpoints.
Virtual links are needed for the following two cases:
Area 0 is discontiguous.
A router is touching two OSPF areas, but is not touching area 0.
If 8, 4, and 5 are your ABRs, they would be the endpoints of your virtual
links.
8 is touching area 22 and 26, but not area 0, so a virtual link is
necessary. The virtual link would be from R8 to R4.
5 is touching area 20 and 4, but not area 0, so a virtual link is necessary.
The virtual link would be from R4 to R5.
Summarization of an area with the area range command is also done on the
area border router. If R7 and R3 are not border routers, they would not
need the area range command.
Marvin Greenlee, CCIE#12237, CCSI# 30483
Network Learning Inc
marvin@ccbootcamp.com
www.ccbootcamp.com (Cisco Training)
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
gladston@br.ibm.com
Sent: Friday, March 04, 2005 12:15 PM
To: ccielab@groupstudy.com
Subject: OSPF summary and multiple ABRs due VL [bcc][faked-from][bayes]
Importance: Low
R7/R8/R4 are connected to area 22.
R8/R11 are connected to area 26
R4/R2/R3 are connected to area 0.
R4/R5 are connected to area 4.
R5/R10 are connected to area 20.
It is required virtual link between R8--R3 (because area 26) and R5--R4
(because area 20).
R8/R5/R4 area ABRs. (originally just R4, but now R7/R5 due virtual link)
Area 22 should be summarized to 172.16.0.0/17.
The router that should be configured with 'area 22 range 172.16.0.0
255.255.128.0' are R7 and R3. This because they are connected to area 11.
Is that correct?
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