This confused me quite a bit too when I was diving into BGP. By my understanding, RD's sole purpose in life is to make BGP prefixes unique. And I would definitely not call them router-local, as the RD value is advertised into BGP with the IPv4 prefix. If you were to create a totally random RD per-router per-VRF, you would end up having a ton of extra prefixes in BGP that are redundant.
Normally, if you have three customer sites that are all on the same VRF, you would want them to share the RD for that VRF. That way, your provider routers can make a BGP best path decision between three BGP advertisements that are for the same MP-BGP prefix (RD + IPv4 prefix). If you were to make each router advertise the same VRF with a different RD...I'm not sure what the consequences would be. I would conjecture that when the router tried to inject multiple BGP prefixes into the same VRF (via RT import), it would only install the "best" BGP option. But each of router P routers would also be processing the same route multiple times, since it thinks that they are different due to different RDs. Does anyone know how this would act? When I come back around to BGP, may have to lab this up to find out! Keller Giacomarro [email protected] On Wed, Aug 15, 2012 at 6:05 AM, Maureen Maina <[email protected]> wrote: > my understanding is that the RD is local to the router and as such can vary > for the same VPN on 2 different routers.The RT is carried with the route > like a tag to identify the routing table/vrf in which it goes. > Regards, > Mo > On Wed, Aug 15, 2012 at 7:55 AM, Keller Giacomarro <[email protected]> > wrote: >> >> Without the RT, how would MP-BGP know which VRF to assign a VPN label to? >> >> Keller Giacomarro >> [email protected] >> >> >> On Tue, Aug 14, 2012 at 10:09 PM, Karan Sagar <[email protected]> wrote: >> > Hi Everyone >> > >> > I'm finding it difficult to understand the role of Route target and VPN >> > labels. >> > >> > Between the PE Routers there is a MP-BGP Session . The MP-BGP protocal >> > carries the Route Distinguisher to uniquely identify routes in the >> > MBGP route table >> > and Route Targets Extended Communtiy are used to determine which >> > interface to forward packets to based on the import and export >> > targets. >> > When there is a neighbor relationship between the CE and PE, Vpn >> > labels are also sent across the PE. The PE router forwards the packet >> > out an interface based on the VPN label. >> > >> > Is the RT required when the VPN label is used to forward packets ? >> > >> > Thanks, >> > Karan >> > _______________________________________________ >> > 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://onlinestudylist.com/mailman/listinfo/ccie_rs >> _______________________________________________ >> 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://onlinestudylist.com/mailman/listinfo/ccie_rs > > _______________________________________________ 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://onlinestudylist.com/mailman/listinfo/ccie_rs
