Re: [OSL | CCIE_RS] Lab 27 - OSPF for Area 115

Michael Senno Tue, 25 Jul 2006 20:20:50 -0700

I was not sure how to do it. What would be the transit area to Area 0 in this case. R4 is attached to Area 115 and Area 15. Area 15 uses Area 1 as a transit, so Area 115 is two areas away. How would the v-link be created?

You guys added the cat to another VLAN and put it in another area. Is this allowed? If so, why not drop it directly into Area 0? The PG specifically says not to, but not why.

What about the default-cost begin 14 instead of 15?

Michael J. Senno

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From: Scott Morris [mailto:[EMAIL PROTECTED]
Sent: Tuesday, July 25, 2006 10:57 PM
To: 'Michael Senno'; [email protected]
Subject: RE: [OSL | CCIE_RS] Lab 27 - OSPF for Area 115

A virtual link does not make you a stub. you can link them together just fine. A virtual link extends area 0 out to the farther ABR.

Was this something you tried on your routers? A GRE is possible as long as the lab doesn't disallow it.

Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIE #153, CISSP, et al.

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From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Michael Senno
Sent: Tuesday, July 25, 2006 10:17 PM
To: [email protected]
Subject: [OSL | CCIE_RS] Lab 27 - OSPF for Area 115

I had some problems with Area 115. I believe that a virtual link can NOT use another virtually linked area as a transit since the v-link makes it a stub. Therefore area 115 would not be able to use Area 15 as a transit, since area 15 is already using a virtual link. The lab gets around that by putting Cat 1 into Area 1 through VLAN 40, however this is not specifically allowed in the lab. The PG does explicitly say that you can't just add it to the IPExpert VLAN though (Area 0). Why can you do one and not the other?

Then, after you do put Cat1 into Area 1 and make the v-link, why do you still need a v-link from r2? Can't Cat 1 act as the virtual link to attach both Area 15 and 115? It appears there is someway that OSPF prevents that, is there somewhere to get a better explanation on this? I believe the issue may be which router r5 and r6 views as the ABR to the transit area, but not sure and also wondering if that would be the same problem for the other v-link?

I'm assuming this has something to do with the fact Cat1 is injecting an default-cost of 14 instead of 15 (its a hop further I guess).

Is a GRE tunnel possible for this scenario?

Please advise. This seems to be a good learning opportunity.