KB 426

Cisco 675/678 NAT: Name server problems...

Article:426
Created:2005-08-02 16:39:03
Categories:
  Modems
  Domain names/DNS
  DSL

Question or Symptom

In CBOS's implementation of NAT, DNS query replies from your name server on port 53 are re-written to reply with the Cisco's WAN IP and a TTL of 0.

Resolution

The workaround for this issue is to create a NAT rule that forwards port 53 UDP packets to your server on a different port. To do this, you'll need to set your name server to reply on a different port (e.g, 5300) and then use this command on the Cisco to create the NAT rule:

set nat entry add <lan ip> <alternate port> 0.0.0.0 53 udp

More information on this issue can be found in the link below.

Related URLS

 http://www.guinix.com/technote/pdxdsl-01.html

Related KB articles

 KB 94 How does one set up port forwarding on the Cisco 675 router?