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Problem with DMZ

Hi all,

I am practising Firewall on GNS3. I have natted DMZ server to Outside IP. I have written an access-list saying permit any source from outside network can telnet a host on DMZ. When I do packet trace from ASDM it works perfectly, even hits access-list . but when I try to telnet host it fails. Rather it never hits access-list in that case. What could be the reason?


Problem with DMZ

Are you still having issues with this?

If so there is a multitude of things that could be happening.  When you say you are have natted the server to the outside IP, are you using PAT natting to only port 23?  have you open only for telnet in the ACL on the outside interface?  are you sure that your device on the outside interface is sending on port 23?  Have you verified that the traffic is actually being NATed?

Another possibility is that this could be a virtualization issue and that deleting the ASA from GNS3 and recreating it will solve the issue.

Would be useful to see a network diagram and the running config if  you still need help.


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Community Member

Problem with DMZ


You can send the packet-tracer output to check the results using CLI, the show run nat output and the acl used in the outside are useful as well. Now, what is the software version used in the ASA? If you use bellow 8.3 the ACL should use your outside ip address from the outside, now if you use 8.3 or later, the ACL should use the 'real ip' of the Server

If everything looks fine maybe there is a virtualization issue....

Community Member

Problem with DMZ

Hi both of you.

I guess it was problem wiith simulation. I used servers instead of routers. Now it is working. And yes, I was using real ip address in acls and translated ip to check them. Well, Thanks for concern. As of now everything is working fine.

Re: Problem with DMZ

Glad you got it working.

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