icmperr during NAT

[mnlatif]

Hi,

I am trying to understand that under what conditions you can see this output

## show ip nat translations

Pro Inside global Inside local Outside local Outside global

icmperr x.x.x.x y.y.y.y --- ---

Where x.x.x.x is the address of the outside nat interface and y.y.y.y is the address for a Network Device on the inside NAT interface subnet.

The inside device is a Vonage Phone adapter and when this error appears i can no longer make phone calls and have to clear the IP nat translations table.

What does icmperr message actually means ?

\\ Naman

[Georg Pauwen]

Hello Naman,

I came across this explanantion for the ´icmperr´ issue:

'icmperr' entry was introduced from 12.1(10.1).

Prior to this version, if a NAT box with overload configured receives an ICMP error message, NAT tries to allocate an address (as opposed to address+port) and to create a simple entry.

This means that if:

- the box is configured with interface overload or

- all the addresses in the overloaded pool are used

the route drops the ICMP error packet...

Now:

Instead of dropping the packet the route just picks any address (from the pool, or from the interface) and it creates a simple entry with a special value in the protocol field (proto=icmperr). This simple entry is used ONLY to translate ICMP errors coming from that particular Inside host.

The entry times out in 1 minute.´

HTH,

GP