> Igor Sukhomlinov > Sent: Friday, April 26, 2019 5:23 AM > > Hi all, > > I wonder if anyone has experience with integrating a UMMT/Seamless MPLS > domain (BGP-LU running over isolated IGP regions) with an existing flat LDP > network. > Yes from well before the term was coined, but that was for the Inter-AS setup. They used to call it hierarchical MPLS or something along those lines. > The customer wants to make sure the existing LDP domain is still running > while the newer BGP enabled domain is steadily coming online, but what is > the best approach to transport the services between the networks? > First of all hierarchical MPLS is not for everyone so the obvious question is do you need to keep the domains separate due to scalability reasons? If not then rather than investing time into "Seamless MPLS" project invest the time into migrating onto common IGP which will result in a much simpler network (IGPs can support huge number of prefixes nowadays and ISIS/OSPF can compute SPF for important prefixes first -and do by default with possibility to customize).
If you are doing this to overcome potential scaling issues, which should be the only reason for doing this, then the easiest and most scalable approach is to leave the individual IGP domains truly separate and have only BGP carry the necessary RIDs/PE-loopbacks along with their respective labels between PEs and ABRs/ASBRs while forming the second (inter-area/inter-as) level of transport labels, which in combination with complete separate process of deriving intra-area/intra-as label-stack will produce the complete end to end label switch path. There's no redistribution involved in this kind of setup (hence no pollution of local intra-area/intra-as IGP), basically clear separation of concerns and all controls or "extras" are kept to the BGP-LU layer. adam _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
