l2 mpls loop prevention

[eicc30000]

how dos l2 mpls prevent loops? l2transport/ vpls. documents are also appreciated

thank you

Glen.

[Peter Paluch · Accepted solution]

Hi Glen,

The loop-free connectivity between PEs is given by the IP/MPLS routing in the core of the provider and it is usually provided by a properly configured and correctly running routing protocol.

The basic pseudowire L2VPN as provided by MPLS does not provide any special prevention against loops. Pseudowires in MPLS L2VPN are point-to-point so a single pseudowire cannot create a loop. If the customer is using several pseudowires that could eventually be chained together to create a loop then it is the responsibility of the customer to avoid such scenarios.

With VPLS, I suggest consulting some of the following documents (also, searching the Google on the "VPLS loop prevention" provides lots of links):

http://fengnet.com/book/layer%202%20vpn%20architectures/ch15lev1sec1.html

http://www.google.sk/url?sa=t&source=web&cd=1&ved=0CBoQFjAA&url=http%3A%2F%2Fwww.cisco.com%2Fapplication%2Fpdf%2Fen%2Fus%2Fguest%2Ftech%2Ftk891%2Fc1482%2Fccmigration_09186a00801ed3ea.pdf&rct=j&q=vpls%20loop%20prevention&ei=_csgTeK7N8y38gPuz4XcBQ&usg=...

Best regards,

Peter

[Yasir Ashfaque]

As mentioned above VPLS uses split horizon loop protection, where traffic received from the network will not be forwarded back to the network.