In mpls-vpn environment P routers forward packets based only on outer label or IGP label. They don't have informations about RD or RT. RD is carried by MP-iBPG, configured on PE routers. RD is used to make the VRF prefixes unique. RT identifies which prefixes import/export in/from VRF. Ultimately, RT is designed to realize extranet VPN comunication. Regards antonio
On 15/01/10 17.54, gökhan duymaz wrote: > Hi Taqdir, > > I think RFC2547 is a good source for a better understanding. As far as I > see, RTs are designed for only remote PE(s) and RDs are designed for all > routers in vpnv4 routing domain . > P routers do not distinguish routes according to RTs they do according > to RDs, and remote PE distinguish routes according to RTs (accept or > not). So RTs are used in remote PEs and RD is used in MP-BGP backbone > -different functions- Why does not remote PE designed do that by looking > at RD? Because each route can have only one RD but multiple RTs. Using > RDs instead of RTs would restrict the design goals. > > Best Regards > Gokhan > > > > > From FRC2547: > > Note that a route can only have one RD, but it can have multiple Target > VPNs. In BGP, scalability is improved if one has a single route with > multiple attributes, as opposed to multiple routes. One could eliminate > the Target VPN attribute by creating more routes (i.e., using more RDs), > but the scaling properties would be less favorable. How does a PE > determine which Target VPN attributes to associate with a given route? > There are a number of different possible ways. The PE might be > configured to associate all routes that lead to a particular site with a > particular Target VPN. Or the PE might be configured to associate > certain routes leading to a particular site with one Target VPN, and > certain with another. > > > > > > > > _______________________________________________ > For more information regarding industry leading CCIE Lab training, please > visit www.ipexpert.com _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com
