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I have set up a Linux server in DMZ.
There is another Windows server running in DMZ.
These two servers can be pinged via internet using my home PC.
However, the another Linux server rented from a hosting service provider can only ping to the Windows Server and not the Linux server (accessed via internet).

So the situation is:

Rented Server ---ping---> Windows server (DMZ).....Successful
Rented Server ---ping---> Linux server (DMZ).......Unreachable
Home PC ---ping---> Linux server (DMZ).......Successful
Home PC ---ping---> Windows server (DMZ).....Successful

Both rented server and home pc are accessing through internet but one can ping while other cannot.
I actually want to ftp the backups of Rented Server to the new Linux Server in DMZ.
Can anyone help what might be wrong?

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2 Answers 2

Sounds like a firewall preventing ping to your linux box, check the firewall rules in router and as well as on linux system

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You can troubleshoot this in a number of ways using tcpdump. Tcpdump comes preinstalled in most Linux distros.

(1) On your Linux server(DMZ) -

tcpdump -i NIC-Interface-here -qn host Rented-Server-IP-here and icmp

for instance, if the DMZ Network card is eth0 and your Rented server IP is 192.168.10.100, you could do

tcpdump -i eth0 -qn host 192.168.10.100

Then start sending ICMP (ping) packets to your Linux server in DMZ from your Rented Server. Do you see the packets? If so, is the Linux box sending back a response.

(2) On your Rented-Server - Just repeat step (1) with the IP address reversed. tcpdump -i NIC-Interface-here -qn host Linux-server-dmz and icmp example: tcpdump -i eth0 -qn host 192.168.10.101

Observer the packets, after pinging the Rented Server from the Linux box in DMZ.

(3) Check your ARP table using the command "arp". Do a "man arp" and add/remove the MAC address of the hosts you are having issues.

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OK. I followed the steps and found the following: My Linux server (DMZ) is receiving the requests and is replying too. However, the Rented-Server is not receiving the pings from Linux Server (DMZ). Does it mean that there some firewall configuration on my rented server? Or could it be some other issue? –  misamisa Dec 10 '12 at 6:45

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