VPN DoS with ASA 5510 and DSL connection

retail · ‎09-29-2007

ASA 5510 Version 7.1(2) ASDM Version 5.1(2)

Scenario: Using Verizon DSL at home, I VPN into my ASA 5510 at work. If the power is accidentally turned off on the DSL modem at home, then I can create a VPN DoS situation with my ASA 5510. This can be recreated every time with my Westell DSL modem (Model #D90-327W15-06.

The effect on the ASA 5510 is to not allow any other VPN connections to attach for several hours later. I allow 3 simultaneous VPN logons on the ASA device so that is not a problem. Is there a bug in this firmware release that I am unaware of. The VPN light on the ASA front panel stays on after the power is turned off on the remote DSL modem. Very strange, you would think the connection would be reset.

If anyone has any information that might help me, I would appreciate it!

Thanks.

amritpatek · ‎10-05-2007

You should enable DPD (dead peer detection) on ASA so that when the vpn goes down the ASA will detect that the peer is not responding and will terminate the connection at its end. This will ensure that the required number of simultaneous logons always remain in safe zone. Following link may help you

http://www.cisco.com/en/US/docs/security/asa/asa72/configuration/guide/svc.html#wp1045952