NEC broadband router: NAT TX-ERROR List Create Error

See also:

• Various hardware notes
  

I have an NEC Aterm WR6650S WarpStar router with firmware revision 8.72. Recently I started having problems connecting to the internet. When I clicked on links in the browser, either it was very slow or it returned an error or times out on me.

Investigating the problem, I finally checked the router log and found error messages similar to this one:

2008/08/24 18:09:29 NAT TX-ERROR List Create Error : UDP 192.168.1.102 : 31320 > 201.29.227.157 : 7701 (IP-PORT=1)
2008/08/24 18:09:29 NAT TX-ERROR List Create Error : UDP 192.168.1.102 : 31320 > 99.227.142.5 : 9205 (IP-PORT=1)
2008/08/24 18:09:29 NAT TX-ERROR List Create Error : UDP 192.168.1.103 : 4643 > 68.175.34.60 : 46438 (IP-PORT=1)
2008/08/24 18:09:29 NAT TX-ERROR List Create Error : UDP 192.168.1.103 : 4643 > 68.184.16.90 : 60440 (IP-PORT=1)
2008/08/24 18:09:29 NAT TX-ERROR List Create Error : UDP 192.168.1.103 : 4643 > 71.98.165.108 : 17631 (IP-PORT=1)
2008/08/24 18:09:29 NAT TX-ERROR List Create Error : UDP 192.168.1.103 : 4643 > 99.227.142.5 : 49078 (IP-PORT=1)
2008/08/24 18:09:29 NAT TX-ERROR List Create Error : UDP 192.168.1.103 : 4643 > 99.129.183.185 : 62634 (IP-PORT=1)
2008/08/24 18:09:29 NAT TX-ERROR List Create Error : UDP 192.168.1.103 : 4643 > 70.210.187.158 : 53379 (IP-PORT=1)
2008/08/24 18:09:29 NAT TX-ERROR List Create Error : UDP 192.168.1.103 : 4643 > 85.180.133.41 : 6906 (IP-PORT=1)

The error message is very unclear and a Google search didn't shed much light on what it really meant, but it probably means the Network Address Translation table of the router is overflowing.

Normally the router would discard old entries in that table after a preconfigured number of seconds and that would be enough to keep it from overflowing as new connections are made to remote hosts, but for some reason it got into a state where this no longer worked.

The temporary fix was to power-cycle the router (unplug its A/C-adapter cord and then reconnect it). This causes the router to forget all existing NAT entries in its RAM and start over from scratch.

I have not observed the problem since then.

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