When I do an MTU test plugged directly into my cable modem my max MTU seems to be set at 1472 (which I get is odd). The really strange part is that when I plug my computer into the Vigor 2960 I can only get a 100% MTU test when its below the routers current MTU set value . For instance, My current router settings is 1472 the highest rating I can get on my PC is 1444. If I set the router to 1100 the highest rating is somewhere near 1000.

Is this normal behavior? Does anyone have any idea what would cause this. My router firmware is up to date. Router settings below

MTU command used:
ping http://www.yahoo.com -f -l 1444

Router settings
Firmware
1.3.0

WAN
MTU: 1472

LoadBalance: Session mode
wan 1: 100/10
wan 2: 100/10

Firewall
Apps: P2P blocking

QoS
HTTP and HTTPS: Medium
Everything Else: Normal

DoS Defence
All Disabled

Session Limiting: 600 Sessions
Bandwidth Limiting:
TX: 1000 kbps
RX: 0

Remeber you should always allow 28bytes for packet overhead, so if the optimum is 1472 then 1444 seems fine

The reverse of this is when you find the max value you can ping with that doesn't fragment - you can set the optimum(forward) MTU to be +28.

If your router is 1100 then you should be able to ping without frag upto 1072