Complex Network Design; L2Tp Troubleshooting - 3Com 3C13636 Configuration Manual

3Com Router 3000 Ethernet Family
Configuration Guide
[RouterB-l2tp1] tunnel authentication
[RouterB-l2tp1] tunnel password simple 3Com
[RouterB-l2tp1] quit
# Configure interface Serial 1/0/0.
[RouterB] interface serial1/0/0
[RouterB-Serial1/0/0] ip address 3.3.3.2 255.255.0.0
[RouterB-Serial1/0/0] quit
# Configure static routing to private network 10.2.0.0
[RouterB] ip route-static 10.2.0.0 16 virtual-template 1
3) Start L2TP connection
# Start L2TP connection in virtual template interface view on Router A
[RouterA] interface virtual-template 1
[RouterA-virtual-template1] l2tp-auto-client enable
Note:
LAC-side router and LNS-side router must be the gateways for their connected private
networks respectively.

2.5.6 Complex Network Design

3Com Routers can serve as LAC and LNS at the same time, supporting multiple
simultaneous incoming calls. L2TP can receive and originate multiple calls as long as
memory and line resources are available. These complex networking requirements and
their configurations can be implemented by referring to above cases.
Pay special attention to the configuration of static route, because many applications are
based on routing to originate calls.

2.6 L2TP Troubleshooting

The VPN tunnel setup process is quite complicated; only several common cases are
analyzed here. Before debugging VPN, please confirm that both LAC and LNS are
connected to a public network, and are connected correctly.
Symptom 1: User's login fails.
Troubleshooting:
Failure causes are as follows:
Fail to establish a tunnel because:
1) On LAC side, LNS addresses are improperly set.
3Com Corporation
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Chapter 2 Configuration of L2TP