NAT Issue

rtjensen4 · ‎06-03-2008

Hello,

I'm hoping a NetPro can help me out. Hanging off my firewall (ASA 5520), I have an interface named "hosted". Off that segment there are two web servers: 192.168.7.14 and 192.168.7.15 Along with a few other servers.

192.168.7.14 has an external IP address of 216.X.X.182. When any internal Users try to hit URL.domain.com which, points to 216.X.X.182 via DNS, the firewall redirects the connection to 192.168.7.14 via the Alias command. My issue comes whenver I try to access the server directly by it's 192.168.7.14 IP address. I don't really understand why I can't access this server. The Log doesn't show any messages as to what's going on with this from what I can see. I flipped the Alias around so it would translate the DNS query (DNS Server sits in DMZ), but then I'm still not able to get to the 192.168.7.14 IP directly. I changed it back so it would just redirect at this point. Our Management server is 10.1.1.25, and sits on the "Inside" of the network. This server has a translation to itself into that network for management of the servers there.

The Users that use these servers the most are at 10.220.9.0 and are Nat-exempted. Everything was setup fine until we had to put the alias in to redirect the connection from the public IP to the private.

Here's the Relevant config:

static (hosted,outside) 216.X.X.182 192.168.7.14 netmask 255.255.255.255

alias (inside) 216.X.X.182 192.168.7.14 255.255.255.255

nat (inside) 0 access-list no-nat

nat (inside) 1 10.0.0.0 255.0.0.0

global (hosted) 1 192.168.7.3 netmask 255.255.255.0

static (inside,hosted) 10.1.1.25 10.1.1.25 netmask 255.255.255.255

access-list no-nat line 1 extended permit ip 10.220.9.0 255.255.255.0 192.168.7.0 255.255.255.0

I did a packet capture on the hosted interface and see what I'd like to see:

1: 16:41:42.064495 802.1Q vlan#33 P0 10.1.1.25 > 192.168.7.14: icmp: echo request

2: 16:41:42.064693 802.1Q vlan#33 P0 192.168.7.14 > 10.1.1.25: icmp: echo reply

The server is responding, but the echo replies are not making back to my managment server. I did a capture on the "Inside" interface and found that the Echo Replys are being translated to the 216.X.X.182 IP. How can I keep this from happening?

So, to make a long story short:

I want the firewall to redirect internal requests to 216.X.X.182 to 192.168.7.14 but I'd also like to be able to access 192.168.7.14 directly.

Is this doable??

Thanks in advance.

JORGE RODRIGUEZ · ‎06-03-2008

This is a perfect example for your scenario.

Look at hairpining and static nat entries section towards the end of this link.

http://www.cisco.com/en/US/products/ps6120/products_configuration_example09186a00807968d1.shtml#problem

We have similar scenario with public servers whereby when access directly from inside we make alias dns entry in our internal DNS servers to use the internal IP for given public dns so inside users can access public srvs internally with internal private IPs, however, I believe above link hairpining should resolve your request.

Rgds

-Jorge

Jorge Rodriguez