[c-nsp] VPLS : Loop avoidance

[Adam Vitkovsky]

Hello Nicolas,

Right the split horizon is there so packets coming from a PW will not be forwarded to another PW in the same VFI so that takes care of loops in MPLS.
However you need to take care of the loops created via LAN/DC side so you need to have a dedicated forwarder for the BUM traffic on one of the ASRs or break the loop.
 
adam
> -----Original Message-----
> From: cisco-nsp [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of
> Nicolas KARP
> Sent: 08 April 2015 15:21
> To: cisco-nsp at puck.nether.net
> Subject: [c-nsp] VPLS : Loop avoidance
> 
> Hello,
> 
> We are going to interconnect two of our datacenters.  In one datacenter we
> have a 6880-X configured with VSS and on the other hand, we have a pair of
> ASR 1001-X.
> 
>  We would like to configure the VPLS and I have some questions about the
> redundancy and loop avoidance. You can find a diagram attached to my
> email..
> 
> 
> *6880 VSS : *
> 
> *l2 vfi VPLS-VLAN-582 manual*
> * vpn id 582*
> * neighbor ASR-2 24 encapsulation mpls*
> * neighbor ASR-1 23 encapsulation mpls*
> 
> *interface Vlan582*
> * mtu 9180*
> * no ip address*
> * xconnect vfi VPLS-VLAN-582*
> 
> 
> *ASR 1: *
> 
> interface GigabitEthernet0/0/5
> service instance 100 ethernet
>   description VLAN582
>   encapsulation dot1q 582 exact
>   rewrite ingress tag pop 1 symmetric
>   bridge-domain 582
>  !
> 
> l2 vfi VPLS-VLAN-582 manual
>  vpn id 582
>  bridge-domain 582
>  mtu 9180
>  neighbor VSS-6880 23 encapsulation mpls
> !
> 
> 
> *ASR 2 : *
> 
> interface GigabitEthernet0/0/5
> service instance 100 ethernet
>   description VLAN582
>   encapsulation dot1q 582 exact
>   rewrite ingress tag pop 1 symmetric
>   bridge-domain 582
>  !
> l2 vfi VPLS-VLAN-582 manual
>  vpn id 582
>  bridge-domain 582
>  mtu 9180
>  neighbor VSS-6880 24 encapsulation mpls
> !
> 
> 
> At the moment, I've enabled one interface on the ASR-1 (g0/0/5), the g0/0/5
> on ASR-2 is still shut.  VPLS is working like a charm between the 6880 and
> ASR-1 but now I would like to activate the second interface on ASR-2 :-)
> 
> I have some doubts about a loop in this case...
> I guess there should be no loop because the 6880 is configured with
> split-horizon but I just wanted to be sure that I will not break my network
> if I activate the second port.
> 
> Can you please help me ?
> 
> Thank you.
> 
> 
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> # - -   Nicolas KARP
> # - -   Network and Security Engineer
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