I just rebuilt my OpenSuSE server with the latest version of Debian. Everything is working fine, except for a slight problem. One out of four PCs on my home LAN is unable to access Google. At first I thought that this was a problem with the PC (such as a hijacked hosts file) BUT...when I connect a Linksys Router in place of the Debian server, the PC can get to Google without a problem. This is a very odd problem, I know. I've tried various things on the PC such as updating the NIC driver. The PC is able to ping www.google.com, so I know that DNS and routing are working. I can even telnet to www.google.com on port 80 and do a successful GET, but neither IE8 or Firefox can load any Google page (including the UK, Canada or Japan).

Wireshark shows quite a few TCP Retransmission packets. Also see a "Destination unreachable" and "Fragmentation Needed" packet returned from the server to the client. No packets are returned from Google that I can see. I can upload the cap file if it will help.

Any ideas? Thanks!

This is probably an MTU mismatch. What is the MTU setting on the PC?

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The MTU on the PC is set to the default value of 1500. Here is what it shows on the server:

eth0 Link encap:Ethernet HWaddr 00:40:63:ed:1b:c0
inet addr:76.104.250.50 Bcast:255.255.255.255 Mask:255.255.248.0
UP BROADCAST RUNNING MULTICAST MTU:576 Metric:1
RX packets:251705 errors:0 dropped:0 overruns:0 frame:0
TX packets:77592 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:72148646 (68.8 MiB) TX bytes:11074185 (10.5 MiB)
Interrupt:10 Base address:0xd000

eth1 Link encap:Ethernet HWaddr 00:40:63:ed:1b:bf
inet addr:192.168.1.1 Bcast:192.168.1.255 Mask:255.255.255.0
inet6 addr: fe80::240:63ff:feed:1bbf/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:143308 errors:0 dropped:0 overruns:0 frame:0
TX packets:240035 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:16733337 (15.9 MiB) TX bytes:112689112 (107.4 MiB)
Interrupt:11 Base address:0xe400

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:49 errors:0 dropped:0 overruns:0 frame:0
TX packets:49 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:2519 (2.4 KiB) TX bytes:2519 (2.4 KiB)

Do you think that the MTU for the external interface should be higher than 576?

Yes. It should be 1500 as well.

The MTU mis-match is why packets are getting bounced as "fragmentation required."

Why would you want the MTU at 576? I'll bet you that the Linksys you mentioned in the origional post is set for 1500.

I didn't set it to 576. It was either Comcast (via DHCP?) or the default in the build. I changed it to 1500 and now Google works fine. To get it to survive a reboot, I first tried adding this line to /etc/network/interfaces:
pre-up /sbin/ifconfig $IFACE mtu 1500

I rebooted and it was still set to 576. I then did this:

Created a file called mtu in /etc/network/if-up.d and added this to it:

#!/bin/sh
ifconfig eth0 mtu 1500

Then I ran chmod 755 mtu

Rebooted and the external interface is set to 1500.

I'm guessing that Google's firewalls must be set to drop fragmented packets. All other sites (Bing, Hotmail, Etrade, etc.) allowed it to work when the MTU was 576. Also strange that it was only failing on my wife's computer and worked on mine (same OS). Thanks for your help. Cheers!

Strangely enough, I appreciate the chance to diagnose this issue, as it is my first "real world" networking problem since I got my CCNA.