Everything was fine before I installed Linksys router at home. I could telnet and ftp from office machine (SGI) to the home machine.

The ISP is earthlink ADSL and the OS is RH7.1.

When I added a router, I did some change on network configuration. The major one is to set my linux machine to be a DCHP client so it can work behind the the router. I can still go out. But problems occur when I telnet and ftp from the remote machines (office machines).

For telnet from office machine, if the echo message is long enough (~20 lines), the two computers stop communicating when the command is issued. This is true for any programs giving echoing message in shell.

For ftp, it doesn't transfer large files. But ftp from home to office works normally under any circumstances.

I can still use graphic editor like nedit from office, although it transfers more bytes.

I tried to forward all ports to the problematic linux machine. But it didn't solve the problem.

It was said there was a firewall (network address translation and TCP/IP port inspections) in the router. Is that the guilty party?

Additional info:

The router is set to forward ports 0-1024 to the linux machine.

Outside the LAN, I can ping the linux machine:
ping -s 1000 (its ip address or name)
but cannot
ping -s 2000 (its ip address or name)

The situation is the same when using a machine inside the LAN.

Within the LAN, I can ping the linux machine by its local address (192.168.1.*) for any sizes.

The problem seems to be related to the size of packets.

My ip is 165.247.33.228, which is dynamically assigned by ISP.