I have two routers that; when first powered up, will initially form full OSPF neighborship with each other and exchange their respective advertised routes with each other. After approximately 2 hours they'll eventually drop their neighborship and routes will be lost. These routers are typically powered off at the end of the day and then brought back up the following day.
I've noticed that their clocks are not in sync. And, to be clear, I'm not referring to whether they are using NTP and/or synchronizing with each other or another NTP server. I simply mean that their time values, when viewing their clocks, do not match. NTP is not being used in this case. Which, I completely understand that; for many reasons, they should be using NTP.
If anyone is curious about what kind of routers these are; they're Linux based (CentOS 6) routers running quagga as their routing daemon.
But with respect to maintaining OSPF neighbor relationships how critical is it that their clocks be close to or in sync with each other? I imagine that there could be some clock drift that occurs when not using NTP. I'm not sure if hold and dead timers could be affected. What other aspects of the OSPF dynamic routing protocol is dependent upon time?