destination host unreachable
 

I have a Red Hat question for you that really has me stumped. I have two different Red Hat 7.3 boxes that both function as cdrw and pure-ftpd servers. I've had them both running flawlessly for about 4 months now, but in the last few days I've rebooted one and then other (for the first time in 4 months). In each case when the machines came back up, they lost network connectivity. Sort of... Any ip address that I ping other than the local host comes back "destination host unreachable". Naturally, I can't ping by f.q.d.n. because it thinks the dns server it's been using all along is also unreachable. I checked the route table against another Linux machine that is working fine and they are identical, except the route table on the two machines that aren't working, the last route entry (the default route) takes an extra few seconds to come up. The last time I did reboot these boxes, they came back up just fine and I don't recall adding any software (or upgrading).

My dilemma is that I haven't changed anything other than simply rebooting them. Any ideas? Or perhaps even what logs I should be looking into to determine a potential problem?

Can you post the output of a netstat -rn ?

Did you manually add the routes or were the added at boot?

Are your Ethernet interface(s) activiated on boot?

netstat -rn
Kernal IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
172.16.0.0 0.0.0.0 255.255.0.0 U 40 0 0 eth0
127.0.0.0 0.0.0.0 255.0.0.0 U 40 0 0 lo
0.0.0.0 172.16.0.1 0.0.0.0 UG 40 0 0 eth0

routes automatically added at boot.

interface enabled at boot.

Do these machines have static IPs or are they using DHCP?

If you could post the output of '/sbin/ifconfig -a', that could be helpful.

Also, you might want to try looking at your system messages log /var/log/messages. (example: 'cat /var/log/messages |more'). There will likely be a LOT of data to read through, so you may want to use grep to look for things like 'eth0', or prehaps search by date (i.e. the date you rebooted these systems).

I hope this helps or points you to the possible culprit.