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MPLS and next-hop-self

lars.molstad
Beginner
Beginner

Hi folks.

I came across a strange configuration of a MPLS network...

The network har two route-reflectors, and all PE's use the route-reflectors - so far it's OK, but... The route-reflectors has the next-hop-self set on all peers in the vpnv4 address-family... Wouldn't that force all traffic from the PE's to go through the Route-reflectors for rerouting?

L@rs

2 Replies 2

mheusing
Cisco Employee
Cisco Employee

Hi Lars,

In principle you would be right, IF the developers would not have been smart. If you configure it or not, a RR will not insert itself as next hop for any client. Makes a lot of sense (at least to the poor RRs ;-) In an MPLS environment, it really would break end-to-end LSPs and thus this single line of configuration could break your whole MPLS VPN BB. Once again, smart thing not to do it whatever the config says ;-)

Hope this helps!

Regards, Martin

Harold Ritter
Cisco Employee
Cisco Employee

Lars,

next-hop-self never affects the reflected updates on the RR. It only affects updates received via eBGP if the RR is also configured for eBGP obviously.

Configuring next-hop-self on the RR is useful in an IPv4 context when your RR is also configured for eBGP. It doesn't apply to VPNv4 though as next-hop-self is the default behavior for routes injected in VPNv4.

Hope this helps,

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
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