problem with re-building TCP/IP connection on Nios

If you mean you can ping and connect with other clients but not with the PC which previously established the connection with the old address, the problem is simple:

The TCP/IP stack has a address table (named ARP table) which stores IP addresses along with the associated MAC address. This avoids the stack to issue a ARP request every time a connection to a known IP is requested: if the IP has already been used, the system already knows where it can be found.

The table is updated continuously when new IP are discovered, but each entry is cleared only after a few minutes (I mean 5 to 10 minutes) the IP address is not used.

Then, if you change the IP address of one of these devices, the ARP table entry is not updated and it would contain mismatched IP and MAC.

If you use Windows you can verify it with the arp -a command which displays the current ARP entries.

Solutions:

- wait the time required for ARP table to be cleared when you change the IP before trying a new connection

- manually clear the ARP table entry at the old IP address: arp -d <old_ip>

I hope this helps you

Cris