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New Member

PAT and an ACL

I was wondering about something today, I have NAT setup on my router between two ethernet interfaces, outside is e0/0 and inside is e0/1, the internet is coming in on e0/0. now lets say that i block a bunch of ports with an acl applied to e0/0 inbound, for example port numbers 7777 and 7778, if pat translates internal streams to the external interface using either one of the ports blocked...what happens? it won't work? time out? do i have to configure a lower timeout level? etc. also what port range does PAT use? above 1023? thanks for your response!!



Re: PAT and an ACL

Yes, PAT uses port nos from 1023 to 65536.

Why do you want to use the same access-list nos for both filtering and for PAT? In this case, PAT will not happen on the specified ports (destination port) due to the deny in the access-list.


New Member

Re: PAT and an ACL

its not that i want to more of a what would happen question. would pat detect that the acl is blocked a port it is trying to pat on? or will it just pat and then that translatino will not work? thanks

New Member

Re: PAT and an ACL

Hi Dear

My name is sukrut and I am trying to use NAT SO that I no need to assign public IP to the my Server for access from remote location.

We are using cisco 3600 Series Router at our central location I have tried to configure NAT on my central router but it not working as some application ports(Range from 1600 -> 3000) which we are not able to access from remote location after configuration of NAT.

Any help.

Best Regards


New Member

Re: PAT and an ACL


From my understanding, the ACL will process traffic first and therefore block packets for destination ports 7777 & 7778 before NAT can perform translation.

The following URL should help: [NAT order of operation]



New Member

Re: PAT and an ACL

Thanks for the link, that helped a lot and put my mind to rest. :)

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