• Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 2313
  • Last Modified:

How do I open UDP port 123 thru the Cisco 1941 router

I am new in cisco, and I have one question about open UDP port 123. I have a 1941 router. I need to open UDP port 123 for to one of my internal server (IP Do I use the following? Thank you in advance.

permit udp eq 123
  • 3
1 Solution
Correct ,But you also need to assign this access-list to an interface.
And also you have decide in which direction it has to assign.

As an example if your is in the range for fast ethernet 0/1 and your Server is in the range of Fast ethernet 0/0 then :

Conf t
ip access-list extended Test
Interface fa0/1
access-group Test in


Thats all.
Sorry i have to correct my previous syntax :

Ip access-group Test in
weikiiroAuthor Commented:
ic, thank you for your help mrmozaffari. for permit udp eq 123, should the external Ip go first or internal ip? I need to establish a 2 way communication.
You did it correctly ,Why ?
Oh just one :
To define a correct access list ; Your syntax is not correct,
Don't Forget Wild card or "Host"
Correct is :

permit udp eq 123


permit udp Host Host eq 123

They are same.

It is the structure of the Extended ACLs :

Permit/Deny Protocol [Source] [Destination]
for permit Rule :

Permit [protocol] [Source address] [Wild card mask] [eq] [port number] [Destination Address] [Wild card mask] [eq] [port number]

Best Regards,
Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

Join & Write a Comment

Featured Post

Free Tool: Port Scanner

Check which ports are open to the outside world. Helps make sure that your firewall rules are working as intended.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

  • 3
Tackle projects and never again get stuck behind a technical roadblock.
Join Now