Linux – nslookup resolves domains to IPs, but I can’t get a response to pings to external servers

centoslinuxnetworkingwindows-server-2003

I have a fresh install of CentOS 4.8 running on an internal development server. I haven't done anything to it besides setting up sudoers and SSH. I can SSH into the server and from there resolve domains to IPs and ping internal servers, but for some reason I don't get any response from pinging external servers.

The software firewall is disabled, and the problem is present with both static and DHCP-assigned network configurations. The network domain controller is a Windows Server 2003 box.

$ nslookup google.com
Server:         10.254.2.5
Address:        10.254.2.5#53

Non-authoritative answer:
Name:   google.com
Address: 74.125.47.147
Name:   google.com
Address: 74.125.47.99
<etc...>

10.254.2.5 is the Win2K3 server.

$ ping google.com
PING google.com (74.125.47.106) 56(84) bytes of data.

It just hangs here indefinitely.

$ cat /etc/resolv.conf
; generated by /sbin/dhclient-script
search <...snip...>.local
nameserver 10.254.2.5
nameserver 10.254.2.124

10.254.2.124 is the backup DC server, which is currently off and tombstoned by this point. The snipped section is our company name.

# ifconfig
eth0      Link encap:Ethernet  HWaddr <snip>
          inet addr:10.254.2.101  Bcast:10.254.2.255  Mask:255.255.255.0
          inet6 addr: <snip>/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:80066 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4421 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:7810133 (7.4 MiB)  TX bytes:590550 (576.7 KiB)
          Interrupt:225 Base address:0xc000

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:32 errors:0 dropped:0 overruns:0 frame:0
          TX packets:32 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:8104 (7.9 KiB)  TX bytes:8104 (7.9 KiB)

# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
10.254.2.0      0.0.0.0         255.255.255.0   U     0      0        0 eth0
169.254.0.0     0.0.0.0         255.255.0.0     U     0      0        0 eth0
0.0.0.0         10.254.2.5      0.0.0.0         UG    0      0        0 eth0

And, for good measure, a snapshot of the current ethernet config via the system-config-network GUI.

Edit: I don't yet have enough rep to post images, so here's a link. Sorry!
system-config-network snapshot

I'm pretty green when it comes to setting up *nix dev servers and network configuration in general, so please let me know if I've left out critical information, or posted information I shouldn't have posted.

Thanks!

Best Answer

Nothing requires that ping be possible between two hosts. It might be that somebody between you and google is dropping ICMP packets. If everything else is working I'd not worry much about this.

If you are particularly worried check with whoever runs your networking equipment or firewall and see if they are letting ICMP traffic through. Also check to see if you can ping anybody else in the outside world other than google?

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