DNS Server not reachable from different subnet intermittently

[baps123]

Hi,

We are having two DNS servers working as master and slave in our DMZ network subnet.DMZ network consist other servers also, but only the DNS servers intermittently becomes unreachable (no ping response) from different subnets whereas the internal communication (within subnet) happens at that time.

From the DNS server we are unable to ping gateway ip also when the issue arises.We tried changing the port where DNS servers connected in DMZ switch and even reformatted the OS and reconfigured DNS but nothing seems to be working.We even tried changing the IP address of the server but after few days the New IP Address also gets affected

We google around a lot tying to fix the issue but no solution has yet come up.We are not even sure whether it is server issue or a network issue.

Please help us resolving the issue.

Thanks in anticipation.

[baps123]

Forgot to add that we are having rhel 5 update 4 in both the DNS servers

Anyone please suggest

[Lazydog]

In the DMZ how many server/devices?
How many of these are showing the same issues?
Have you checked the routing table on the router for the DMZ?

[baps123]

we are having around 10 servers in DMZ zone, only 2 DNS servers showing this issue.

Other servers running mail, webserver, oracle stack having no issue.

As the problem is intermittent I believe routing table is fine

[rituraj.goswami]

Thatz very strange.can u plz submit a diagram plus the routing tables. Mayb i could try recreatg the scenerio.

[Lazydog]

What are you using as a router/firewall?
Do the logs on the DNS servers show anything?