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KB-10598: addns gets IP of the Cisco NAT instead of the IP of the host

Authentication Service ,  

1 October,18 at 03:39 PM

Problem:

Updating DNS on Linux that is Cisco NAT'ed using addns gets the IP of the NAT and not the IP of the host.

The windows systems on the same network are registering correctly in DNS.  It's just the linux systems using Centrify that aren't working.

On a Linux box with Centrify agent installed, let's call it Client A with a made up IP of 1.1.1.1.

There is the DNS server and let's call it Server A.

When Client A issues the addns command to update the DNS server, Server A, we would expect a host record of 1.1.1.1 with a hostname of Client A be placed into DNS for both forward and reverse lookup zones.

When Client A sends the addns command to Server A, it passes through a Cisco router. This router does a one to many NAT for all the clients talking to it. So, when the IP of 1.1.1.1 gets to the router, it gets NAT'ed to a new address, say 2.2.2.2.

The DNS server receives the request from the addns command, but instead of placing the IP of Client A in the DNS table of 1.1.1.1, it places the IP of the NAT, 2.2.2.2 as the IP of Client A.

Resolution:

The following config needed to be added to the private Cisco CSRs.

no ip nat service all-algs
no ip nat service dns-reset-ttl

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