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Beginner

how do we check for open ports on a router ?

how can we view all the open ports on a router (if your sourcing from an outside IP) ?

can we view open ports by using 'show' commands ?

thanks.

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Rising star

Re: how do we check for open ports on a router ?

Hi there,

I can't remember the command off the top of my head, but try something along the lines of:-

"show ip socket" or

"show ip tcp brief" or "show tcp brief"

Not too sure which one it is, but one of them will give you a good idea. Failing that - grab a port scanner, there is a great one called "the dude" and another good one called nmap. Pop them into google.

Hope that helps,

LH

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10 REPLIES 10
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Re: how do we check for open ports on a router ?

All ports are open, by default, on a router. If you aren't blocking any ports with an ACL then you can safely assume all ports are open.

HTH

Sundar

Highlighted
Contributor

Re: how do we check for open ports on a router ?

Do you mean all ports the router would accept connections on? Connections directed to the router? Usually port 23 for telnet and 80 for HTTP access....

I don't know if this answer your question. In case you mean what ports are allowed, if you have inspection enabled everything from outside will be denied unless you allow them by an ACL on the outside interface.

Hope the above could help,

Please rete if Icould help,

Highlighted

Re: how do we check for open ports on a router ?

Hi,

Even if you had CBAC (inspection) configured on the router you would have to apply an ACL on the outside interface to block everything coming in. The router would inspect all the traffic from inside and create dynamic ACE(s) in the ACL, applied on the outside interface, for the return traffic to be allowed back to the inside host.

HTH

Sundar

Highlighted
Rising star

Re: how do we check for open ports on a router ?

Hi there,

I can't remember the command off the top of my head, but try something along the lines of:-

"show ip socket" or

"show ip tcp brief" or "show tcp brief"

Not too sure which one it is, but one of them will give you a good idea. Failing that - grab a port scanner, there is a great one called "the dude" and another good one called nmap. Pop them into google.

Hope that helps,

LH

Please rate all posts

View solution in original post

Highlighted
Beginner

how do we check for open ports on a router ?

exactly "show ip sockets"

tks!

Highlighted
Beginner

Re: how do we check for open ports on a router ?

show ip ports all 

Highlighted
Beginner

Re: how do we check for open ports on a router ?

Hi there,

 

I have issue with sending email out  from my network.

 

Email setting on host:

 

smtp server name : smtp.gmail.com

smtp port number : 465

 

 

How do i check whether smtp port 465 is opend in cisco router ?

 

Router model is 3925.

 

Thank you.

 

Highlighted
Beginner

Re: how do we check for open ports on a router ?

Hi

I think, you can try " show ip nbar port-map " command, this will give you list of tcp and udp ports, this command support certain router.

Please rate this post.

-minu mathur

when you use ip helpe address method, then following UDP ports are by defaul open

1) TFTP-69

2) DNS-53

3) Time-37

4) Netbios name services-137

5)Netbious datagram services-138

6)BOOTP server-67

7)Bootp client-68

8) Tacacs-49

Please rate this post

Highlighted
Beginner

Here is your answer:show

Here is your answer:

show control-plane host open-ports

 

HTH,

MS

Highlighted
Beginner

Re: how do we check for open ports on a router ?

The show IP socket would give you more insight of what you need.

Please do not hesitate to click the STAR button if you are satisfied with my answer.