Converting from ISAKMP to PKI

Convert from ISAKMP to PKI without any downtime.

Converting from ISAKMP to PKI
Tom Lancaster

As the adoption of VPN technology grows, so do the management headaches. Many administrators have seen the number of IPSec tunnels in their network grow quite rapidly. And what was once a simple ISAKMP pre-shared key exercise may now be getting out of control. These administrators are looking for scalable solutions, and the trend seems to be towards using the PKI infrastructure and Certificate Authorities.

If your network fits this description and also has a high-availability requirement, you may be wondering how in the world to convert from using pre-shared keys to Certificate Authorities without extended service outages. Well, don't panic. There is an easy way to convert from ISAKMP to PKI without any downtime at all!

The trick is to create a crypto map statement that uses the PKI, and give it a higher priority than the crypto map that uses pre-shared keys. To do this, make sure the sequence number on the PKI crypto map is LOWER than the sequence number of the pre-shared key crypto map.

Then, just let the SA expire! By default (in Cisco IOS) an ISAKMP SA will last 86,400 seconds (one day) and an IPSec SA will last 3600 seconds (one hour) or until 4500 Mb have been transmitted. But, 30 seconds or 256Kb before the SA is set to expire, ISAKMP will renegotiate the SA (this time choosing the more preferred PKI option) and no disruption of service will occur!


Thomas Alexander Lancaster IV is a consultant and author with over ten years experience in the networking industry, focused on Internet infrastructure.

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Related Book

PKI: Implementing & Managing E-Security
Author : Andrew Nash, Derek Brink, William Duane and Celia A. Joseph
Publisher : Osborne
Published : Mar 2001
Summary :
Written by the experts at RSA Security, this book will show you how to secure transactions and develop customer trust in e-commerce through the use of PKI technology. Part of the RSA Press Series.


This was first published in July 2001

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