1. Notating the RD in each VRF, and controlling the communities in MBGP is
how you separate routes/address spaces per VPN. That specific information
is used to filter the routes you do or do not pay attention to. If you look
at the bgp database, it would be horrendous. but the filtering in the VRF
import/export allows these separate routing tables to be much more sane.
2. That is mostly correct. MBGP peers will exchange ALL information, but
it won't get entered into anyone's routing table unless there's a VRF import
or a route to synchronize with (standard BGP operation). The BGP database,
by default, is completely separate from the normal routing table.
3. Yes, RD's are locally significant. If you use them globally, you may
make things better for yourself. I believe it's RFC 2574 that lays out the
structure.
4. Again, it would be helpful, but not necessary...
5. Labels play a role, but like normal BGP operation, you're simply trying
to determine who the next hop (or exit point) is, which would be the PE
router on the other end. Labels can be used to get there, or normal IP
routing to the IP address of the last PE necessary. Whichever works for
your network.
Scott
-----Original Message-----
From: Vinod Anthony Joseph Cherunni [mailto:vac@dsqworld.com]
Sent: Thursday, October 05, 2000 10:04 AM
To: smorris@mentortech.com
Cc: cisco-nsp@puck.nether.net
Subject: RE: [nsp] REG: MPLS VPN route exchange
Hi,
Thanks a lot the advice. I have a few more doubts, Kindly help me out.
They are -
1. Even if I use multiple instances of a routing protocol per VPN, How
will I be able to control what routing information will flow to which PE
router. Also how will I be able to indcate which address space is associated
with which VPN, when routing information exchange happens.
2. I personally feel that the "route target import/export" command defined
while creating the VRF, restricts what information is exported & imported &
to which RD. This information is further considered by MBGP &only
appropriate information is exchanged with peers. This co-ordination is
unavailable with the use of IGP for doing the job. Kindly correct me if
wrong.
3. Are RD's locally significant, or is an identifier assigned to all
connected sites of a VPN.
4. In the cases, wherein we peer with other service providers, do the RD's
need to be unique across the network.
5. Now the routing information of VPN's are only exchange between the Edge
routers (PE), How will the Provider core routers be aware of it, & how does
forwarding happen at the Core. Do lables play a role here, If so can you pls
explain how it happens.
Kindly advice.
With kind regards,
Vinod.
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