Solved

cisco router - ip insepct interface

Posted on 2013-01-24
2
371 Views
Last Modified: 2013-01-25
I am trying to determine if it matters which interface I apply the "ip inspect" too on a cisco ios router/firewall.  

From reading up on the "ip inspect" it says that if you have the "ip inspect" the return traffic will bypass any ACLs.    In the below example will the return traffic still bypass the ACL 100 on Fa0/1 even if the inspect is applied to Fa0/0.

internal network: 192.168.1.0/24

interface FastEthernet0/0
 description Internal Network
 ip address 192.168.1.1 255.255.255.0
 ip access-group 101 in
 ip inspect FWINSPECT in
 ip nat inside

interface FastEthernet0/1
 description Connection to the Internet
 ip address 1.1.1.2 255.255.255.252
 ip access-group 100 in
 ip nat outside


Thanks
0
Comment
Question by:tiptechs
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
2 Comments
 
LVL 20

Expert Comment

by:rauenpc
ID: 38815263
I believe it will work regardless of interface, but if you only have one inspection policy, I would put it on the outside interface so that any other inside interfaces, whether existing today or configured in the future, all end up getting covered by that policy.
0
 
LVL 15

Accepted Solution

by:
Frabble earned 500 total points
ID: 38816382
Where you do the inspection depends on the router/firewall topology. To say that return traffic bypasses ACLs is incorrect. CBAC dynamically modifies ACLs to allow the flow of return traffic and data channnels in FTP for example.

If you regard the router interfaces as internal and external, "inspect in" the internal or  "inspect out" the external would modify the incoming access list on the external interface and outgoing list on the internal interface.

In the example above, the inspect in on internal Fa0/0 will modify the acl 100 in on external Fa0/1 to allow the return traffic.

There is all the detail here:
http://www.cisco.com/en/US/docs/ios/12_1/security/configuration/guide/scdcbac.html
0

Featured Post

Announcing the Most Valuable Experts of 2016

MVEs are more concerned with the satisfaction of those they help than with the considerable points they can earn. They are the types of people you feel privileged to call colleagues. Join us in honoring this amazing group of Experts.

Question has a verified solution.

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

Occasionally, we encounter connectivity issues that appear to be isolated to cable internet service.  The issues we typically encountered were reset errors within Internet Explorer when accessing web sites or continually dropped or failing VPN conne…
Imagine you have a shopping list of items you need to get at the grocery store. You have two options: A. Take one trip to the grocery store and get everything you need for the week, or B. Take multiple trips, buying an item at a time, to achieve t…
There's a multitude of different network monitoring solutions out there, and you're probably wondering what makes NetCrunch so special. It's completely agentless, but does let you create an agent, if you desire. It offers powerful scalability …
In this video we outline the Physical Segments view of NetCrunch network monitor. By following this brief how-to video, you will be able to learn how NetCrunch visualizes your network, how granular is the information collected, as well as where to f…
Suggested Courses

623 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