MPLS CHAPTER 6

MPLS CHAPTER 6
QUUESTIONS :

20. In MPLS L3VPN how do the customer & provider share routes ?
21. Why does a PE have a VRF for each customer ? What is VRF ?
22. Which protocol is used between PE's to advertise VPNv4 routes ?

Solutions :
20. In MPLS L3VPN how do the customer & provider share routes ?
21. Why does a PE have a VRF for each customer ? What is VRF ?

HOW MPLS L3VPNs Work
. MPLS L3VPNs have two basic components
. Separation of Customer routing information
-Virtual Routing & Forwarding VRF instance
- Customers have different "virtual" routing tables
. Exchange of customer routing information
- MP-BGP over the MPLS network
- Traffic is label switched towards BGP next-hops

VRF
. each VRF has its own routing table
- show ip route vrf [name | * ]
. Interfaes not in a VRF are in the global table
- show ip route
. VRF and global routes are separate
- implies addressing can overlap in different VRFs
- implies VRFs cant talk to each other because they have no
   routes to each other
. VRFs without MPLS is considered "VRF Lite"

PE routers stores routing table of all the customers:
as shown in diagram:

22. Which protocol is used between PE's to advertise VPNv4 routes ?

Multiprotocol BGP
 . RFC 4364 "BGP/MPLS IP Virtual Private Networks (VPNs) "
 - MP-BGP define AFI & SAFI 128 as VPN-iPv4 or VPNv4