Strange network issue in freebsd 8

[Sherin George]

Hello,

i am facing some sort of strange network issue in a freebsd server
occasionally.

OS: FreeBSD 8.0-RELEASE - amd64

The servers loses network connection once in a few days. I logged into
console and verified that network is up. I even restarted network service
using following command.

/etc/rc.d/netif restart

Still, it didn't fix.

I checked /var/log/messages, but I am not getting any clue.

==============
Jan 19 12:10:20 myserver kernel: GEOM_MIRROR: Device gm0: rebuilding
provider ad0 finished.
Jan 19 20:20:23 myserver nfsd[732]: select failed: Interrupted system call
Jan 19 20:21:07 myserver nfsd[732]: select failed: Interrupted system call
Jan 23 02:14:33 myserver login: ROOT LOGIN (root) ON ttyv0
Jan 23 02:19:51 myserver kernel: ifa_del_loopback_route: deletion failed
Jan 23 02:19:57 myserver kernel: em0: link state changed to DOWN
Jan 23 02:20:02 myserver kernel: em0: link state changed to UP
Jan 23 02:29:58 myserver reboot: rebooted by root
Jan 23 02:29:58 myserver syslogd: exiting on signal 15
Jan 23 02:31:31 myserver syslogd: kernel boot file is /boot/kernel/kernel
Jan 23 02:31:31 myserver kernel: Copyright (c) 1992-2009 The FreeBSD
Project.
Jan 23 02:31:31 myserver kernel: Copyright (c) 1979, 1980, 1983, 1986, 1988,
1989, 1991, 1992, 1993, 1994
Jan 23 02:31:31 myserver kernel: The Regents of the University of
California. All rights reserved.
Jan 23 02:31:31 myserver kernel: FreeBSD is a registered trademark of The
FreeBSD Foundation.
Jan 23 02:31:31 myserver kernel: FreeBSD 8.0-RELEASE #0: Sat Nov 21 15:02:08
UTC 2009
Jan 23 02:31:31 myserver kernel: root at mason.cse.buffalo.edu:
/usr/obj/usr/src/sys/GENERIC
Jan 23 02:31:31 myserver kernel: Timecounter "i8254" frequency 1193182 Hz
quality 0
==============

Network, TCP stack all were up. It was pinging gateway even. But, traceroute
was not going beyond gateway.

I believe the issue is not related to anything outside server since a reboot
always fixes the issue.

I will be grateful for any advise that can help me in troubleshooting this
problem.

--
Best Regards,
Sherin