The reason you should want Area0 on both sides is for fault tolerance. If you use one you will have discontiguous area 0's.
Regards, Tyson Scott - CCIE #13513 R&S, Security, and SP Managing Partner / Sr. Instructor - IPexpert, Inc. Mailto: <mailto:[email protected]> [email protected] Telephone: +1.810.326.1444, ext. 208 Live Assistance, Please visit: <http://www.ipexpert.com/chat> www.ipexpert.com/chat eFax: +1.810.454.0130 IPexpert is a premier provider of Self-Study Workbooks, Video on Demand, Audio Tools, Online Hardware Rental and Classroom Training for the Cisco CCIE (R&S, Voice, Security & Service Provider) certification(s) with training locations throughout the United States, Europe, South Asia and Australia. Be sure to visit our online communities at <http://www.ipexpert.com/communities> www.ipexpert.com/communities and our public website at <http://www.ipexpert.com/> www.ipexpert.com From: [email protected] [mailto:[email protected]] On Behalf Of Joshua Yost Sent: Thursday, June 10, 2010 9:46 AM To: ccie_rs Subject: Re: [OSL | CCIE_RS] Sham WOW part 2 Any takers? On Tue, Jun 8, 2010 at 3:42 PM, Joshua Yost <[email protected]> wrote: I asked something similarly weird earlier, then gave up on it, but now I have been testing it and am just confused Here's situation 1: R1------AREA0-----R2----------AREA111---------R3----------MPLS-------------- R4---------------AREA 222------------R5 Now, without a virtual link through area 111, area 0 and area 111 are isolated, and only know OSPF information from each other. This makes sense. Now if I extend a virtual link through area 111 to the PE, I have reachability to the Area 222. To break this down, and all sham link configurations set aside, if I have area 0 at any site in my MPLS VPN topology (as the customer), I must extend it to the MPLS with a virtual link? Is that right? Now, on to situation 2: R1------AREA0-----R2----------AREA111---------R3----------MPLS-------------- R4---------------AREA 222------------R5----------AREA 222---------R1 Note this is a circle with R1 being an ABR for areas 0 and 222. Loopbacks are all R.R.R.R R1s loopback is in area 222 R2 L0 in area 0 R5 L0 in Area 222 So you can probably see where this is going, R5 - R1 would be my good ol "Backdoor link" Right now with no manipulation, R2 gets to R5's L0 via R1 and the backdoor link. In fact regardless of manipulation this is the case. Now, I want all traffic from R2 to area 222 to go over MPLS. So I configured the virtual link through 111 as described in the previous example, then I configured an area 0 sham link over MPLS. Then magically, I can route however I want over MPLS by playing with cost. Specifically, if I want R2 to get to R5's loopback via MPLS, I just cost up the link between R1 and R2 on R2. None of this works without the sham link, but I thought we needed area 0 on both sides of the sham link for this to work? Is there an exception? The sham link is acting kinda like a virtual link but not really. HELP
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