MPLS over IPv6

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Nov 4th, 2008
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In one of the Cisco configuration guide I read: "

Before the IPv6 Provider Edge Router over MPLS (6PE) feature can be implemented, MPLS must be running over the core IPv4 network. If Cisco routers are used, Cisco Express Forwarding (CEF) or distributed CEF (dCEF) must be enabled for both IPv4 and IPv6 protocols. This module assumes that you are familiar with MPLS."

Does it means my interface on each and every routers should be dual stack to support the MPLS as it said to enable MPLS on IPv4 network?

so what if I have only IPv6 addressing in the network! and want to run MPLS VPN on IPv6 network?

how can i enable the MPLS in my IPv6 network?


Devang Patel

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Giuseppe Larosa Tue, 11/04/2008 - 09:58
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Hello Devang,

only the PE routers , 6VPE are dual stack, core routers P nodes are based on MPLS and IPv4.

6PE and 6VPE have been developed as evolution paths for current ISPs with an MPLS/IPv4 infrastructure.

Current Cisco implementation hasn't an IPv6 ready LDP so you still need an IPv4/MPLS core.

Restrictions for Implementing IPv6 VPN over MPLS

6VPE supports an MPLS IPv4-signaled core. An MPLS IPv6-signaled core is not supported

the scenario is exactly similar to IPv4 MPLS L3 VPNs: P routers know nothing about Vpnv4 routes and their labels.

A double level MPLS stack do the job.

This shouldn't be a great limitation if you start from an MPLS/IPv4 backbone.

Hope to help


devang_etcom Tue, 11/04/2008 - 11:23
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Okay thats fine when you have IPv4 core and running dual stack on PEs... but what if I will have all my routers including P and PE running only IPv6 then how to configure VPNv6 for that?

how mpls will be enabled in the network?


Devang Patel

Giuseppe Larosa Tue, 11/04/2008 - 11:40
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Hello Devang,

currently you cannot use MPLS over an IPv6 only core.

However, you can deploy a private ip address plan per RFC1918 infrastructure this is only a workaround.

I don't know if there is a road-map for this feature but I agree that is wellcome and desired.

Hope to help


Mohamed Sobair Mon, 11/10/2008 - 23:23
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you cant run IPv6 on MPLS natively yet...

three solutions to deploy IPv6 Over an MPLS:

1- 6PE ( In this type the PEs are dual Stack , P routers are IPv4s , but you should configure the address-family IPv6 at the bgp process to send labels in order to label IPv6 Packet.

2- 6VPE (In this type , PEs are also dual Stack, P routers are IPv4s, and you dont have to explicitly label IPV6 packet since address-family VPNv6 is configured to carry IPv6 Labeled packet between PEs.

3- MPLS-VPN solution (In this type , MPLS provider is pure IPv4, CEs should implement one of the tunneling techniques to carry IPv6 Over IPv4. those tunneling could be:

a- IPv6 over IPv4

b- 6 to 4

c- IPv4 to IPv6 compatible



Harold Ritter Tue, 11/11/2008 - 11:42
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You could also run IPv6 over L2VPN.


tarjbains Tue, 11/11/2008 - 13:37
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my freind i have one Q. for MPLS TE. i m using 3660 router for MPLS TE on dayanagen simulater. in this lab there is 5 routers with 512 kbp RSVP on each interface all router with MPLS TE. configure are as->

R1 /0 ---R2 /0

R2 ==== R3 have Two interfaces s1/1 and s1/3

R2 /2-----R5 /2 interface connection

R3 ---- R5 int connection

R3 ---- R4 tunnel to R4 from R1,R2 with 300kb each

tunnel1 on R1 to R4 with 300kb rsvp TE

tunnel2 on R1 to R3 with 50kb rsvp TE

tunnel1 on R2 to R4 with 300kb rsvp TE

diagram like that below (ignore ..dots)




i created tunnels from R1----> R4 with 300Kb.

second R1---->R5 with 50Kbp tunnel


on R2---->R4 tunnel with 300kbp.

PROBLEM IS when R1 tunnel go via R2 to R4 it takes s1/1 interface with 300rsvp. means for R2 tunnel should find next interface for same destination R4 becaused there is not enough space.On one of remaining on interfaces on R2 s1/3 or S1/2 but R2-->R4 tunnel remain down. when i down R1---R4 tunnel R2--R4 tunnel comes up on same interface. NOW when i up R2 tunnel first and later R1. then same thing again R1 down and wait for R2 tunnel to go down.then up on same interface. if u see there is still two path r free to go R4 on R2

1. R2 s1/3 ----> s1/3 of R3

2. R2 s1/2 ---->s1/2 of R5 with both 512 kb RSVP

there is using R2 s1/1 for tunnel

why not with help of CSPF it takes other path when 512 link is also free on R2 router to same destination??? its on dyanamips is it can problem with simulater.

it means that on R2 using SPF path for R4 for both tunnel and not trying to find other CSPF path thats why my two interfaces are free with 512kbp RSVP on same router R2. why not CSPF using other remaining path. and down one of tunnel because of there is no space on tht s1/1 interface........


Mohamed Sobair Thu, 11/13/2008 - 02:20
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Yes Harold correct, In (AToM) where the payload is layer-2 (PPP,HDLC, Ethernet , FR , ATM).

Thanks for clarification.




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