How can I change MTU on FastEthernet port (Cisco 7206)

try #ip tcp adjust-mss 1360

Unfortunately, this command is not present in this version of the IOS. Also is not enough RAM and FLASH  for upgrade to new IOS. there are more ideas?

Some platforms just won't let you change the MTU. There is an interface config command that tells OSPF to ignore the MTU if that helps.

"ip ospf mtu-ignore"

#mtu 1524
#ip mtu 1524

Here's the Cisco documentation description of the difference between the 2 commands.

 

Protocol-Specific Versions of the mtu Command

Changing the MTU value with the mtu interface configuration command can affect values for the protocol-specific versions of the command (the ip mtu command, for example). If the value specified with the ip mtu interface configuration command is the same as the value specified with the mtu interface configuration command, and you change the value for the mtu interface configuration command, the ip mtu value automatically matches the new mtu interface configuration command value. However, changing the values for the ip mtu configuration commands has no effect on the value for the mtu interface configuration command.

 

So it comes down to affecting all protocols, or just IP traffic.

do you have both fast and gig-Ethernet port in your router?

I have command "ip ospf mtu-ignore" in my configuration, but it affected only for OSPF connectivity.
Unfortunately, I haven't gigabit ports on my routers. There are more ideas?