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Tariqemad
Beginner

NAT Command Line

Hi all, 

Kindly, any one can advice me about the purposes for the below command line in ASR1002.. Thanks in advance 

ip nat settings nonpatdrop

 

Spoiler
 

 

3 REPLIES 3
lespejel
Participant

it looks like a legacy command for Carrier Grade NAT not present in the documentation, but it should enable a particular NAT mode.

 

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipaddr_nat/configuration/xe-3s/nat-xe-3s-book/iadnat-cgn.html

 

 

CCIE 52804

this command drops all packets which can not be Port Address Translated (non pattable trafffic). PAT can only be performed
on protocols where the ports are known : UDP, TCP, ICMP

 

If the router receives a non pattable packet, a static translation entry is created (1:1) and therefore a pool exhaustion is likely. Either make sure that only the above mentioned protocols hit the router or enable this command to avoid pool exhaustion. The documentation explains that pretty well:

 

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipaddr_nat/configuration/xe-16-9/nat-xe-16-9-book.pdf

 

Andre