Wireless Adapter in WinXP Pro Capped at 1300 MTU

[Jim Yohn]

I have circumstance where the wireless connection I'm using in my Windows XP
Professional PC is getting capped at 1300 MTU. Unless a wireless adapter is
meant to be capped at 1300 (I don't know that much about wireless), I'd like
to bring the MTU up to 1500 and improve transmissions.

The other (wired) PC in my home network can get 1500 MTU, so I don't believe
the local router is limiting it. I verified the wireless adapter MTU is
1300 by pinging the router/AP and external IP addresses with this command:

ping <dest> -f -l 1272. where <dest> is any of the addresses I've tried.

Any packet size higher than 1272 gets a response "Packet needs to be
fragmented but DF set." With 28 bits tcp/ip adds due to error checking,
etc., 1272 = 28 = 1300 MTU.

I have no MTU values set in the registry for the interface (or anywhere).
I've tweaked tcpip settings with cablenut to optimize the transmit/receive
window sizes (*after* identifying the 1300 MTU cap). The wireless link to
the router/AP is where the MTU limit is in effect (the 1st hop).

Any ideas for a way to increase the MTU using this adapter?

Thanks,
Jim

 

[peter]

Have you tried going into the router settings(internet explorer) and looked for
a MTU setting ??
On my Netgear Wireless router there is such a setting.
peter