TCP MSS Adjustment

It was a bit puzzling at first since you could ping these sites but could not access them via a web browser. The problem was the MTU setting.

The soultion was to use specify the MTU setting on each interface.

ip mtu 1492
ip tcp adjust-mss 1452

If you were wondering what ip tcp adjust-mss 1452 does it modifies the maximum segment size (MSS) for TCP SYN packets traveling through the interface (see link below for more information).

TCP MSS Adjustment
http://www.cisco.com/en/US/docs/ios/12_2t/12_2t4/feature/guide/ft_admss.html