Cisco ASR 1002-X and PPTP

Problem: PPTP from any client to an ASR1002-X Cisco does not work. PPTP Connections starts but in PPP LCP phase the connection fails.

Solution: Cisco ASR1002-X with Software IOS-XE 15.3(2)S2 has no PPTP support. You have to take a different Router!

Discussion: The weird thing is, that most of the PPTP stack is still configureable and working, but all packets coming from the client inside the PPTP tunnel are dropped!

Some examples:

.) #show vpdn tunnel
%No active L2TP tunnels
%No active PPTP tunnels

.) in vpdn-group you can set protocol any

.) the router is answering PPTP (TCP 1723)

.) the router starts the PPP layer when a connection is coming in

.) the router even sends LCP O CONFREQ packets to the client

But! The Cisco ASR Router drops every LCP I CONFACK coming from the client.

Cisco was always a reliable piece of hardware for me, but this looks like they removed a feature without removing the code and their QA department worked like this: “it compiles, ship it”.


Multiple Routing Tables with IPTables

Challenge: You have a linux based firewall, which should forward all internal and external traffic of its connected clients through a VPN tunnel, and at the same time the traffic from the firewall itself should not go through the tunnel (e.g. the tunnel connection packets).

Solution: There are lots of howtos for this probably. Here is my very simple and quick  (3 lines) solution.

Mark all packets that should go through the tunnel:
> iptables -t mangle -A PREROUTING -s ! -d -i eth1 -j MARK –set-mark  3

Setup a second routing table:
> ip route add table 3 default dev tun0

Add a rule to use routing-table 3 for packets marked with 3:
> ip rule add fwmark 3 table 3 client IPs
tun0: device of the vpn tunnel