L2TP Client: Cisco
Cisco routers running IOS 12.3(2)T and later support L2TP client initiated tunneling which allows the router to establish an L2TP tunnel to A&A's L2TP server.
Most of the information required was gleaned from here:  plus a bit of trial and error and some packet capturing of good and bad L2TP sessions.
I have tested this on a Cisco 837 router running 12.3(11)YZ2, a 2821 running 12.4(15)T10 SPServices and a 2801 running 12.4(24)T3 ADVIPServices
- You will need to sanity check routing in your particular environment. This is especially important if you choose to use ppp ipcp route default on the l2tp tunnel. It's safest to make sure that you have a static route set to the L2TP server.
- I haven't tested this for IPV6 yet.
- This is "early release" information - I haven't yet used this in anger over a long period of time but will try to remember to come back and update if I find any major issues.
- This config snippet contains no security settings - be sure to configure some!
- I've used the IP address of the L2TP server rather than the DNS address - this is obviously at risk of change .
- You need to be running IP CEF on the router
Replace <whatever> with the appropriate information for your connection
ip cef l2tp-class lc-aaisp pseudowire-class pc-aaisp encapsulation l2tpv2 protocol l2tpv2 lc-aaisp ip local interface <interface that l2tp connection should go out from> interface Virtual-PPP9797 shutdown ip address negotiated no cdp enable ppp authentication chap callin ppp chap hostname <l2tp line login eg firstname.lastname@example.org> ppp chap password 0 <site password> ppp direction callout ppp pap refuse pseudowire 126.96.36.199 10 pw-class pc-aaisp
Once the interface is configured you can issue a no shut on it to bring it up.
debug ppp authentication and debug ppp negotiation are your friends... In particular if you see "Circuit ID not set - contact support" in the authentication debug, contact A&A support to get them to fix your L2TP login.
Once the connection is up, you should see the virtual PPP interface configured with the static IP that is assigned to it in clueless.
If you get stuck, pop into the IRC channel and see if I'm around (basil_uk) and I'll help if possible.