I could use some help troubleshooting a problem. We have a Cisco 2821 ISR router that is doing NAT, CBAC, and reporting NetFlow to a NetFlow monitor. The problem we are having is at random sites will become unavailable or extremely slow. What is odd though is that if you keep hitting retry the page will load just fine after some time. Persistent application such as instant messaging programs will also disconnect at random.
NetFlow and a ?show int? confirm that usage is not anywhere near the max, even on the Internet-facing interface. CPU usage also rarely tops 30%.
Can anyone give me some tips on how to troubleshoot this? If I enable ?ip inspect audit-trail? I am inundated by 50+ messages a second from connections being created then torn down. Can anyone help think of any way of logging that might provide some insight into what might be going on? Because of the very random nature of the problem, it never happens when I do it, and by the time someone gets to a command prompt to try and ping or tracert, the problem is already gone. But I am thinking somewhere a log has to be screaming.
Here is a snip of the code to get an idea what the router is doing:
ip inspect name CBACout ftp
ip inspect name CBACout http
description Internet Outside
ip address 126.96.36.199 255.255.255.252
ip access-group ACLin in
ip access-group ACLout out
ip nbar protocol-discovery
ip nat outside
ip inspect CBACout out
no ip route-cache cef
no ip route-cache
no cdp enable
ppp multilink group 1
description Inside Interface
encapsulation dot1Q 1 native
ip address 10.1.1.1 255.255.0.0 secondary
ip address 10.2.1.1 255.255.0.0 secondary
ip address 10.2.3.254 255.255.0.0
ip access-group ACL1_out in
ip nat inside
no ip route-cache
ip nat inside source route-map nonat interface Multilink1 overload
ip access-list extended ACL1_out
permit ip any any reflect ACL1_RACLin
ip access-list extended ACL_nonat
deny ip 10.0.0.0 0.255.255.255 188.8.131.52 0.255.255.255
deny ip 10.0.0.0 0.255.255.255 10.0.0.0 0.255.255.255
permit ip 10.0.0.0 0.255.255.255 any
ip access-list extended ACLin
permit ip 10.0.0.0 0.255.255.255 10.0.0.0 0.255.255.255
permit icmp any any echo
permit icmp any any echo-reply
permit icmp any any host-unreachable
permit icmp any any net-unreachable
permit icmp any any time-exceeded
permit icmp any any ttl-exceeded
!Snip - Bunch of explicit allows to connect to internal servers
Thank you for the reply! I am running 12.4(15)T1, and have tried to run the latest 12.4 non-T train. Both have the same effect.
I disabled process switching, that must have been old config from when I was trying to get the NetFlow monitor to work. I re-enabled CEF on all the interfaces to see if that fixes the problem.
I have a mix of reflexive ACLs and CBAC because I must not be understanding CBAC properly.
I have not found any examples of mixing NAT and CBAC together. All the examples use CBAC on the inside interface in the inbound direction to create ACL entries on the ACL on the outside interface in the inbound direction. What doesn't make sense is CBAC on the inside would be putting an inside IP address, not the NATed IP address into that ACL.
Do you use NAT and CBAC on the same router? Can you give me an example of what your config looks like that you are only using CBAC? I would greatly appreciate it!
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
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