LNS and Subscriber Management

[dfranjoso]

Hello Guys,

Is it possible to terminate the L2TP session on one router – the LNS – and handover the traffic to other router for Subscriber management?

Thanks!

David

[Manuel Rodriguez]

Hi David,

The scenario is not entirely clear tome. However, from what you say, perhaps L2TP multihop can be an option?

http://www.cisco.com/en/US/tech/tk801/tk703/technologies_configuration_example09186a0080094ab7.shtml

Best regards.

[dfranjoso]

Hello Manuel,

Thanks for you reply. Our problem is this:

• We terminating a L2TP session in a 2951 - our LNS.
  
• But we want to execute the Subscriber management on another router - a 9K (which doesn't support the LNS feature).
  
• So our idea (if possible) is to terminate the L2TP session on the 2951 (LNS) an then handover traffic to the 9K for all Subscriber management. We hope this is possible to be done.
  

Once again, thanks Manuel for your time.

David

[Manuel Rodriguez]

Hi David,

Indeed, ASR9k doesn't provide LNS functionality. What you could do is to use BNG IP sessions to treat the traffic coming from the LNS. You could for example send the traffic on one vlan between those 2 devices and then use IP sessions on the BNG subinterface to initiate the session.

Some documents that may be interesting for this:

https://supportforums.cisco.com/docs/DOC-23170

http://www.cisco.com/en/US/docs/routers/asr9000/software/asr9k_r5.1/bng/configuration/guide/b_bng_cg51xasr9k_chapter_0101.html

Be aware that, in your case, you would normally need IP routed type of sessions since, from BNG perspective, the access network would be routed. I did some internal research here and I believe this type of sessions are available as of XR 5.1.1, so take that into account.

I would also suggest to contact your Cisco Account Team to have a proper design advise for this.

Hope this helps.

Best regards.

[m-burrows]

Thanks Manuel.

As far as i can see, this way, the subscriber will still needs to be authenticated on the LNS and a local IP addressing Pool still needs to be in configured to assign a IP Address to the Subscriber. Our intention was to bridge the PPPoE traffic untouched to the 9K, and let the 9K to execute any Subscriber management, including AAA and ip addressing assignment.

[Manuel Rodriguez · Accepted solution]

Hi,

I understood that the L2TP session would be terminated on the 2951 and then the IP traffic would be forwarded to the ASR9k.

In the case you are describing, I cannot think on an easy solution. The ideal would be VPDN multihop but is not available on asr9k (AFAIK). That's why I proposed to perform the subscriber management directly on the IP traffic using IP BNG session. But indeed, that solution will not perform AAA or address allocation on the PPP session itself as the session would be just IP traffic for the BNG. The IP session can still be authenticated on BNG but the L2TP session will remain up on your LNS.

As I said, I would suggest to your Cisco Account Team so they can propose a solution (you may need to use a different platform which can do VPDN multihop like an asr1k).

Sorry I couldn't help more.

Best regards.

[dfranjoso]

Thanks Manuel!