Hi Adam, You are very right. In the scenario I last mentioned, I was using EIGRP as the protocol :)
Regards, Samir. On Wed, Jun 8, 2011 at 5:02 AM, Adam Booth <[email protected]> wrote: > Hi Samir, > > Well a distribute-list is one way to do it if you want to have selective > control, otherwise if the CE-PE and backdoor protocol is OSPF and you want > to save the backdoor link for protection only, I would suggest you just set > the interfaces on the backdoor link to have a higher ospf cost than the > accumulated cost across the provider network. > > Cheers, > Adam > > > On Tue, Jun 7, 2011 at 11:05 PM, Samir Idris <[email protected]> wrote: > >> Adam Adam! >> >> Thanks alot for the explanation. Really appreciated. >> >> I did put in a backdoor link when lab'ing it up. Certainly route over >> backdoor was preferred due to the cost to I manipualted it. >> >> I lab'ed up similar stuff but with EIGRP as a CE-PE protocol. Here I >> tried soo and it worked fine. In all the examples I saw on the web I didn't >> see any metric manipulation being done and so the backdoor link was being >> preferred. I used distribute list at the CEs connected via backdoor to make >> the path preferred over MPLS network. Is it the right way? >> >> Thanks again. Regards, >> Samir Idris. >> >> On Tue, Jun 7, 2011 at 5:21 PM, Adam Booth <[email protected]>wrote: >> >>> Hi Samir, >>> >>> If the OSPF process id is the same at either end of the provider network, >>> there is an implied domain-id set by IOS but if you are using different >>> process ids to get alignment you need both sides to have a common domain-id >>> only if you want routes to appear as inter-area rather than external >>> routes. If domain-ids are in alignment then routes over the provider >>> network will appear as inter-area (type 3) otherwise routes will appear as >>> external (type 5) >>> >>> To have routes appearing as intra-area via the provider network shamlinks >>> are required, as they are similar to a virtual-link but can extend any OSPF >>> area, not just area 0 over the provider's network (type 1) - as you have >>> found, the domain-id doesn't matter here. >>> >>> The value of a sham-link is meant to be if you have a backdoor link (not >>> using the provider network) that is in the same area, you aren't going to >>> get into problems where intra-area routes are always preferred over >>> inter-area routes (should the backdoor link be in the same OSPF area) >>> however I think for the backdoor link you're probably going to have to >>> manipulate the link costs to be less preferred than the MPLS network anyway, >>> so you may as well give the backdoor link a different OSPF area - which I >>> think kind of negates the need for a sham-link in the first place :) >>> >>> Cheers, >>> Adam >>> >>> >>> On Tue, Jun 7, 2011 at 9:02 PM, Samir Idris <[email protected]>wrote: >>> >>>> Hey Hey, >>>> >>>> I have lab'ed up a scenario where EIGRP is running as an IGP in the MPLS >>>> core. I am using OSPF as an IGP between PE-CE at both the sites. >>>> >>>> 1)- If I create a sham-link with NO domain-id, the routes appear to be >>>> intra-area. It makes sense as sham-link is like a virtual-link over >>>> MPLS. >>>> Please correct me if wrong. >>>> >>>> 2)- If I add domain-id and different ones still the routes appear to be >>>> intra-area. Is it because domain-id doesn't take effect or what? >>>> Confused >>>> at this point >>>> >>>> 3)- If I remove the sham-link and simply use same domain-id at both PEs >>>> I >>>> get inter-area routes. This one makes sense as the BGP community >>>> carries >>>> the domain-id along with it. The PE looks as it and knows how to >>>> manipulate >>>> it. >>>> >>>> I am confused at point 2. Can anyone explain please? Thanks. >>>> >>>> Regards, >>>> Samir Idris. >>>> _______________________________________________ >>>> For more information regarding industry leading CCIE Lab training, >>>> please visit www.ipexpert.com >>>> >>>> Are you a CCNP or CCIE and looking for a job? Check out >>>> www.PlatinumPlacement.com <http://www.platinumplacement.com/> >>>> >>> >>> >> >> >> -- >> Samir Idris >> > > -- Samir Idris _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com Are you a CCNP or CCIE and looking for a job? Check out www.PlatinumPlacement.com
