Solved

PIX 6.3: ACLs and Security Levels

Posted on 2006-06-21
3
480 Views
Last Modified: 2010-04-08
I'm reworking my PIX configuration to get rid of conduits in favor of ACLs.

My question is regarding how ACLs and the security levels of the various interfaces interact.

Since every access-list ends with an implicit deny all statement, does this override the fact that higher security interfaces can usually get to lower security interfaces?

For example, if I apply an ACL to my DMZ interface (seclevel 50) permitting access to a server behind my inside interface, will the implicit deny at the end of the ACL prevent things in the DMZ from accessing the Internet (i.e., networks on the outside, seclevel 0 interface?)
0
Comment
Question by:titan6400
  • 2
3 Comments
 
LVL 25

Assisted Solution

by:Cyclops3590
Cyclops3590 earned 50 total points
ID: 16955039
yes.  dmz clients will no longer reach anywhere to the internet after you apply an interface.

if you want that functionality you need to make explicit rules to handle what you want
lets say you have 192.168.1.x as your inside network and 192.168.2.x as your dmz
you want 192.168.2.10 to talk to 192.168.1.5 web purposes for some reason, you'd need to add

access-list dmz-in permit tcp host 192.168.2.10 host 192.168.1.5 eq 80
and apply it to the interface. of course that essentially add this line to the end of the acl
access-list dmz-in deny ip any any
so what you want to do is after that first acl add these lines to keep the functionality of the security levels
access-list dmz-in deny ip 192.168.2.0 255.255.255.0 192.168.1.0 255.255.255.0
access-list dmz-in permit ip any any

of course if there are any other networks on a higher security level interface, you'd need to add those rules in as well and make sure they are before that last permit any any line
0
 
LVL 79

Accepted Solution

by:
lrmoore earned 75 total points
ID: 16955047
Yes...
All traffic from higher security to lower security (inside-->outside, inside-->DMZ, DMZ-->out) is permitted by default. Use acls only to restrict outbound traffic.
All traffic from lower to higher (outside-->DMZ, outside-->inside, DMZ-->inside) is blocked by default. Use access-lists for exceptions.
Yes, if you do something like this:
 access-list DMZ permit ip host <dmz host> host <inside host>
 access-group DMZ in interface DMZ

It will now block all other traffic into that interface. You have to be careful:
 access-list DMZ permit ip host <dmz host> host <inside host>
 access-list DMZ deny ip any <inside subnet>
 access-list DMZ permit ip any any

Of course, you are also constained by the static NAT between inside and DMZ, so you may want to do a same/same nat for the inside host to dmz:
 static (inside,dmz) <inside host ip> <inside host ip> netmask 255.255.255.255

0
 
LVL 25

Expert Comment

by:Cyclops3590
ID: 16955237
forgot about the translation entries
btw, you'll also need
static (dmz,inside) <dmz host ip> <dmz host ip> netmask 255.255.255.255

of course I prefer
static (inside, dmz) <inside subnet> <inside subnet> netmask <inside subnet mask>
static (dmz, inside) <dmz subnet> <dmz subnet> netmask <dmz subnet mask>

but that is mostly because i'm lazy and it covers the entire subnet right away instead of doing a lot of static entries to cover individual hosts
0

Featured Post

PRTG Network Monitor: Intuitive Network Monitoring

Network Monitoring is essential to ensure that computer systems and network devices are running. Use PRTG to monitor LANs, servers, websites, applications and devices, bandwidth, virtual environments, remote systems, IoT, and many more. PRTG is easy to set up & use.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

If you have an ASA5510 then this sort of thing would be better handled with a CSC Module, however on an ASA5505 thats not an option, and if you want to throw in a quick solution to stop your staff going to facebook during work time, then this is the…
Have you experienced traffic destined through a Cisco ASA firewall disappears and you do not know if the traffic stops in the firewall or somewhere else? The solution is the capture feature. This feature was released in 6.2(1) and works in all firew…
Both in life and business – not all partnerships are created equal. As the demand for cloud services increases, so do the number of self-proclaimed cloud partners. Asking the right questions up front in the partnership, will enable both parties …
As a trusted technology advisor to your customers you are likely getting the daily question of, ‘should I put this in the cloud?’ As customer demands for cloud services increases, companies will see a shift from traditional buying patterns to new…

777 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question