MPLS minimum config

[ChrisNewnham_]

Am I right in thinking the minimum config to get an MPLS L3 VPN up and running is:

1) OSPF or another routing protocol in the provider network, including a loopback address (let's say Lo0). Not required on PE-CE interfaces.

2) MP-BGP between PE's, usually via a route reflector (RR), using VPNv4 and possibly VPNv6 address families. Peer using Lo0 interfaces as these will be used as the next hop for CE learned routes advertised into the provider space.

3) "Some" routing protocol between PE-CE, doesn't really matter but if not BGP will need to be redistributed into MP-BGP by the PE.

4) MPLS LDP on the PE Lo0's, and all transport links between PE's. I don't think the P's Lo0 needs to be advertised in LDP?

Thanks!

[M02@rt37]

Hello @ChrisNewnham_,

Find below, some additional details:

-Routing Protocol in the Provider Network:
Typically, an IGP like OSPF is used within the provider network. Loopback addresses (Lo0) are commonly used for stability and to provide a stable router ID for OSPF. This helps in avoiding flaps in the network.

-MP-BGP Between PE Routers:
MP-BGP is used between PE and P routers to exchange VPN routing information. VPNv4 or VPNv6 address families are used to carry customer routes. RR are often employed for scalability in larger MPLS networks.

-Routing Between PE-CE:
You need some form of routing between the PE and CE routers. It could be a dynamic routing protocol (like OSPF, EIGRP, or BGP) or static routes. If using BGP, it's common to redistribute the customer routes into MP-BGP for propagation across the MPLS network.

[MHM Cisco World]

all points correct 
last point Q 
no need LDP in LO of any PE.

[ChrisNewnham_]

Thanks MHM, but I thought that if Lo0 is being used as the MP-BGP peering IP inside the provider network, you would need to advertise it inside LDP as it's used as the MP-BGP VPNv4/v6 next hop?

[MHM Cisco World]

LO is next-hop of BGP VPNv4  which is reachable via interface that run LDP 
second LDP is between two peer, LO is one end so no need LDP (I assume even if you want to run command mpls ip under LO the router refuse it).

[Martin L]

MPLS and OSPF used heavily in RS track on Cisco exams; there is one-action command to turn on LDP on all OSPF running interfaces; The command is  mpls ldp autoconfig  goes under router ospf x

MPLS and IS-IS used by ISP and SP track ..... and most importantly ip cef must be turned on to run LDP at all

Regards, ML
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