I've been trying to find the best solution for the following problem.
As I understand it, for me to send IP traffic to an ISM or VSM on an ASR9k for CGN(ex: NAT44), the solution would be to use ABF and configure the ISM/VSM as next-hop for pre-NAT outgoing traffic. My question is this: ABF deployment guide says that ABF does not support mpls-labeled traffic, in other words if an IP-packet I want to NAT comes in labeled, ABF would not be able to catch it an redirect it to VSM so it would be NATed. Can anybody share a posible (best) solution to this scenario?
indeed, our NPU will perform the ACL matching before handling the labels and therefore the labelled-traffic can not be matched. In other words, you can not apply ABF to push traffic to the CGN card if you are a PE box.
First approach will consist in making the penultimate router responsible for discarding the labels, at least for the traffic candidate for NATing.
Second, some customers overcome this limitation using a "loop" cable. Your label will be stripped and only IPv4 packet will get back inside the chassis and therefore can be matched by your ABF.
I understand that none of these options are satisfactory or technically elegant...
That's exactly the point, in my environment my PE (in this case a CMTS running mpls for l3vpn) has to have labels for L3VPN setup. This PE also has Internet access service. It connects to 2 ASR9000 P routers, that are the correct place for me to install an ISM or a VSM. So basically, the originating router would 'have to do PHP'.
So basically, for me to get to the CGN card, as far as I can tell, my 'only' option is the loop. I saw this being described in a CiscoLive presentation. Let's forget for a moment that is not an elegant solution, we're talking 10-20G of traffic here per POP. I cannot fathom telling my customer they have to invest in the CGN card AND 2-4 10G interfaces per loop, per ASR.
Seems to me it makes sense to work on ABF being able to catch mpls labels.
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