CSC - label distribution to MPLS VPN provider

Unanswered Question
Jan 17th, 2008

Hi guys,

our company ( we are not a MPLS VPN provider) has self deployed MPLS i.e. EoMPlS, MPLS TE & fast reroute for FCIP and MPLS VPN for Guest network.


We also have a need to distribute our labels to remote sites so that we could deploy EoMPLS. remote sites are connected via a MPLS VPN provider which provides a BGP handoff.


i tested a design where labels would be advertised to ISP-MPLS-CLOUD and then to remote sites via BGP. ( "neighbor x.x.x.x send-label" on CE and PE BGP process).


(all links in campus - from distribution block to core swtich and from core switch to CE router are enabled for tag-switching.)


I tried to implement that design with the ISP's help yesterday: i was able to extend labels to remote sites successfully, however one remote site created a big problem. From the headend CE when i traced route to remote site core switch i was seeing very odd behavior. There was a loop: packet was going out the PE router and then back to CE router ( ce router has a remote site(Z) connected via point-to-point T1 and it is NOT MPLS enabled) and then to remote site Z and then back to the CE router and from here the same trip again.


once i reverted back the changes every thing went back to normal.



do i need any of following commands:


?mpls ip default route:

- we are advertisint a default route to all remote sites.

? do i need to configure "neighbor x.x.x.x explicit-null"


Any other ideas - i have not been able to re create this problem in my dynamips routers.


appreciate any input


Umar



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mheusing Fri, 01/18/2008 - 04:42

Hi Umar,


typically in MPLS the path is determined by the IP routing. What were your changes to the IP routing in the CE/PE environment?

Did you do more than the "neighbor x.x.x.x send-label", f.e. change the PE-CE routing protocol to BGP or modify redistribution or CE-CE iBGP, etc.?


Regards, Martin

uchaudhry Fri, 01/18/2008 - 06:17

hey Martin : thanks for your reply.

Actually "neighbor x.x.x.x send-label" was the only change. We moved to BGP few months ago. When i was trying to trouble shoot i had tunred off IBGP between two heand end CEs and EBGP on the redundant CE router eliminating any potential.


I have verifed IGP routing to see if any thing is misconfigured but have not found any thing YET.

Also after turning off BGP label distribution that loop stopped which makes me think that label switching has some thing do with it.


I had asked the Provider to check the next hop and the outgoing interface of the route i was traceroute-ing to and it checked out.

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