topic ASA 8.2 multiple nat statements? in Network Security

ASA 8.2 multiple nat statements?

3moloz123 — Tue, 12 Mar 2019 01:57:16 GMT

Hi,

I would like to config "when host X on vlanX goes to a network that is across an ipsec tunnel, for which vlanX network is not in the encryption domains, translate host X address to that of the asa in a network that is part of the crypto domain".

Interface vlan544 (172.16.80.0/24) is the local encryption domain, and 10.1.0.0/29 holds some monitoring servers that should not be part of the encryption domain, but rather get it's source address translated to that of the firewall in 172.16.80.0/24. Here's how I did:

# Vlan522 for 10.1.0.0/29, need to somehow have a specific nat here I guess that falls between the no nat and the generic "nat the rest to the global)

nat (vlan522) 0 access-list vlan522_nat0_outbound

nat (vlan522) 1 0.0.0.0 0.0.0.0

# Next, I defined an ACL to match the source network (10.1.0.0/29) with the remote encryption domain (172.18.0.0/24):

access-list prtg-to-slott-net extended permit ip 10.1.0.0 255.255.255.248 172.18.0.0 255.255.255.0

# Removing the global nat on vlan522:

no nat (vlan522) 1 0.0.0.0 0.0.0.0

# Set up the newly defined access-list as nat entry 1 instead

nat (vlan522) 1 access-list prtg-to-slott-net

# Re-adding the catch all nat but this time as rule number #2

nat (vlan522) 2 0.0.0.0 0.0.0.0

This obviously didn't work, the second (number 2) rule is never hit. What am I doing wrong?

ASA 8.2 multiple nat statements?

Jouni Forss — Thu, 13 Jun 2013 09:48:40 GMT

Hi,

I got a bit confused reading that

So did I understand correctly that the situation is the following

You have existing L2L VPN connection configured between 1 local network and 1 remote network
You would want to configure a second local network to be able to use the L2L VPN connection without changing the L2L VPN configurations?

In this case you should probably do the following

Determine a free IP address that is not used in the original local network that is part of the L2L VPN currently
Configure a Dynamic Policy PAT for it

access-list L2LVPN-POLICYPAT permit ip 10.1.0.0 255.255.255.248 172.18.0.0 255.255.255.0

global (outside) 100 172.16.80.254

nat (vlan522) 100 access-list L2LVPN-POLICYPAT

There is ofcourse a chance that some existing NAT configuration makes this one useless but for that we have "packet-tracer" command to determine which configurations are hit when the traffic arrives to the ASA

packet-tracer intput vlan522 tcp 10.1.0.2 12345 172.18.0.100 3389

The port and IP address values I used are random and can be pretty much anything. Ofcourse the mentioned traffic needs to be allowed in the interface ACL or the "packet-tracer" hits and ACCESS-LIST DROP.

- Jouni

ASA 8.2 multiple nat statements?

3moloz123 — Thu, 13 Jun 2013 09:58:30 GMT

Jouni, you're really picking my questions and answering them one by one. You provide good short explanation, I now see the connection between the nat (int) VALUE and global (int) VALUE.

Thanks!