PCs using certain IP addresses cannot ping out.

Hi,

I'm having a very strange problem which I just can't get past.

The way our network is set up, we have 2 locations. The main office with all our PCs, and servers/ We are then joined to a local ISP via microwave link and they provide our internet gateway and house an additional storage server for us. All of the network infrastructure is within our office

The problem is...

When some PCs (and servers) are assigned IP addresses, they cannot ping the gateway or remote server however the remote server can ping the PC.

Most of our internal IP addresses work fine but specific ones (e.g. .29) has this problem all the time.

There is nothing else using the ip address and no other network problems. When we switch the IP on the PC, it works fine.

Please help, I'm going mad.

Thanks,

Steve

From serverfault Steve McCall

• I would suspect that the restriction is occurring at the firewall. Check its logs at the time of the failed ping and see if the activity is recorded. If so, check what rule is causing this.

  Steve McCall : The traffic doesn't pass through the gateway when accessing the remote server and only passes through windows firewalls.

  PMGoldstein : Is it possible that the port on the firewall is set to only receive IPs of a specific IP range? For instance, I know that if I have a Sonicwall port defined to receive 192.168.1.100-192.168.1.200 and I plug a machine into it with an IP of 192.168.5.100, the connection will simply fail.
  From PMGoldstein

• There are several possible explanations for this, but the two top probability explanations to me are:

  A) Bad network configuration on the hosts. One way to verify could be to show us the configs, telling which OS/distribution, whether you're using DHCP and so on. Or you could assign the problem addresses to different hosts.

  B) firewalling or incorrect routing on the gateway or even on the problem hosts themselves.

  We'll need more information about your experiments to know for sure.

  Steve McCall : Mostly DHCP addresses, some static (servers etc) I tried switching the ips to different hosts and still had the same problem. Strangely though the offending ip I was testing is now working fine a few days later...

  Steve McCall : The traffic doesn't pass through the gateway when accessing the remote server and only passes through windows firewalls I still find it very strange that the host with the problem could not ping the remote server or gateway but the remote server could ping the problem host
  From dotplus