Yes, your RD and VRF name is only locally significant. The main purpose of an RD is to make a prefix look unique for BGP. Think about how regular prefix exchange works with BGP. If BGP has two routes that look the same it will only advertise the *best* one, the same thing will happen with MBGP in a MPLS/VPN exchange, so in order for BGP to advertise all the routes, it has to look different hence the different RD added to the prefix. That is all.
On Fri, Jan 15, 2010 at 7:07 AM, Taqdir Singh <[email protected]>wrote: > I think RDs can be different on both PE routers for the same customer and > even VRF names can also be different. > > > On Fri, Jan 15, 2010 at 6:38 PM, marc abel <[email protected]> wrote: > >> The way I understand it is the remote recieving router uses it to >> decide which RT's to look at. For example say your remote PE has >> connections to both customer A and B. The route arrives with the RD A >> 10.0.0.0/8, ok then look in the RD A set of RT's, ok those RT's tell >> us to import this route. Now something arrives with RD B 10.0.0.0/8, >> now look in the RD B set of RT's to decide if we should import. >> If something just arrived 10.0.0.0/8 how would it know which RT to use? >> >> >> On Fri, Jan 15, 2010 at 6:38 AM, Taqdir Singh <[email protected]> >> wrote: >> > Hi Marko, >> > >> > Thanks, but please help me in understanding more on this.. >> > >> > Suppose we have One PE router (Se0/0 is connected to customer A (VRF A), >> > Se0/1 is connected to customer B that is VRF B >> > >> > When route (10.0.0.0/8) hit on se0/0 from customer A router, PE >> router >> > will put those routes in VRF A routing table >> > >> > and >> > >> > when route (10.0.0.0/8) hit on se0/1 from customer B router, PE router >> will >> > put those routes in VRF B routing table. >> > >> > and then finally MP-BGP will send those VPN prefixes to Remote PE router >> > >> > and remote PE router will only just match RT and then will put into >> > corresponding VRFs. >> > >> > So when we say RD keeps the prefixes unique by adding RD in front of it >> but >> > in what manner ? >> > >> > we have RT that is also going along with it and on remote PE only RT is >> > checked and on the remote end also customer A route 10.0.0.0/8 will be >> put >> > into VRF A by matching its RT and customer B route 10.0.0.0/8 will be >> put >> > into VRF B by mathcing its RT >> > >> > So all the way along where is RD actually helping in keeping the routes >> > unique ? >> > >> > >> > >> > On Fri, Jan 15, 2010 at 3:45 PM, Marko Milivojevic <[email protected] >> > >> > wrote: >> >> >> >> > I know RD keeps 10.0.0./8 of customer A separate from 10.0.0./8 of >> >> > customer >> >> > B. >> >> >> >> And this is good understanding. Now, for the final bit - that's the >> >> ONLY thing it does! >> >> >> >> > But if the final import export is done on the basis of RT, where RD >> is >> >> > actually being compared ? >> >> >> >> Nowhere. The only purpose of RD is to keep prefixes "unique", i.e. >> >> allow overlapping IPv4 address space by prepending them with RD. >> >> >> >> -- >> >> Marko Milivojevic - CCIE #18427 >> >> Senior Technical Instructor - IPexpert >> >> >> >> Mailto: [email protected] >> >> Telephone: +1.810.326.1444 >> >> Fax: +1.810.454.0130 >> >> Community: http://www.ipexpert.com/communities >> > >> > >> > >> > -- >> > TAQDIR SINGH >> > Network Engineering >> > (+91) 991.170.9496 | (+91) 801.041.5988 >> > >> > One who asks is a fool for a moment, one who doesn't ask remains fool >> for >> > ever >> > >> > _______________________________________________ >> > For more information regarding industry leading CCIE Lab training, >> please >> > visit www.ipexpert.com >> > >> > >> > > > > -- > TAQDIR SINGH > Network Engineering > (+91) 991.170.9496 | (+91) 801.041.5988 > > One who asks is a fool for a moment, one who doesn't ask remains fool for > ever > > _______________________________________________ > For more information regarding industry leading CCIE Lab training, please > visit www.ipexpert.com > > -- Sergio Danelli JNCIE #170
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