Thanks for the quick reply.
I'm only looking for Jumbo Frames over the LAN with wired connections to the DIR-855.
So, when you say NAT I'm a bit confused.
I thought NAT was Network Address Translation and didn't apply to my wired LAN connections.
Is this not the case?

If it is, would using static IP addresses allow me to use jumbo frames?
I'm also running multiple NICs in these machines to multiple subnets.
One subnet is the DIR-855 and the other is the DGL-4100.
I am able to configure the DGL-4100 to jumbo frames so maybe I'll just use that subnet for NAS access.
Then use the DIR-855 subnet for http, ftp, etc.
One final thought, I'm also running Vista on these wired computers so wouldn't the use of IPv6 eliminate the need for NAT ?