IPsec has gone into block mode

We have a single Windows SBS2003 running exchange, which when recently restarted, could not ping / access any other IP addresses on the network. On looking at the event log, I noticed that an error reported that IPsec had gone into block mode, and on researching this, established that we should dissable the IPsec service and reboot the server.

This we did, and sure enough it resolved the issue.

My question is, why would this suddenly happen, and do we need IPsec running on the server.

We use OWA, RDP, and SMTP which are all currently working fine.

Any advice would be welcomed.

Many thanks.
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It's due to a race condition where another serivce reserves the ports before IPSEC does. Issue and fix documented here:

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