From: Serhat Aslan (serhatworks@gmail.com)
Date: Fri Jul 13 2007 - 20:49:00 ART
Hi Micheal,
Virtual-links are have to be on ABRs(transit state). Transit-Are logic is
the opposite of stub network, so we can't use virtual links on the stub
networks.
We use gre tunneling to join the bad design stub/normal-networks for area 0
integration. But in this case we have to care the hop-count problem
(route-flapping)
note0: ABR = area 3 + area 4 capability
note1: nssa = stub area +lsa7 advertisement
note2: virtual-link :
<snap-for transit area>
http://www.faqs.org/rfcs/rfc2328.html
Virtual links are part of the backbone, and behave as if they were
unnumbered point-to-point networks between the two routers. A
virtual link uses the intra-area routing of its Transit area to
forward packets.
</snap-for transit area>
---- Serhat AslanOn 7/14/07, Jason Guy (jguy) <jguy@cisco.com> wrote: > > If you have to connect area 0 to a remote area (ie one that does not > have a direct interface connection to area 0), then typically you use a > virtual link from an existing area 0 ABR to the ABR of the area you need > to connect to area 0. > > In the case of stub or nssa being the transit area, you are not allowed > to use a virtual link. So in this case you have to create a tunnel, and > put that tunnel interface into OSPF area 0 on both ends. Now the remote > area has an interface in area 0. > > As for the method of bringing up the tunnel, that can be tricky. You > have to make sure the tunnel source and destination addresses area > routable in the transit area. So if you use ip unnumbered, make sure > the address is reachable across the transit area. Also make sure the > source and destination addresses do not become reachable via the tunnel, > or you will see the tunnel interface go up and down repeatedly. > > HTH > Jason > > > -----Original Message----- > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf > Of M > > S > > Sent: Friday, July 13, 2007 4:56 PM > > To: ccielab@groupstudy.com > > Subject: tunnelingOSPF > > > > Hello: > > This is my most dreaded topic. > > Can i get some clarrification on how to use tunnels to replace ospf > area > > virtual-links over stub and nssa areas? > > For virtual links that do not have a common area 0 on both sides one > > should place an ip address on the tunnel > > > > For virtual links that have an area 0 on both sides of the stub area, > I > > think i can use an ip unnumbered interface. > > > > Is this right. > > Thanks > > > > > ------------------------------------------------------------------------ > > > > See what you re getting into before you go there > > > > > _______________________________________________________________________ > > Subscription information may be found at: > > http://www.groupstudy.com/list/CCIELab.html > > _______________________________________________________________________ > Subscription information may be found at: > http://www.groupstudy.com/list/CCIELab.html
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