I have a strange problem - after rebooting my Cisco 867 router running IOS 15.5 all inside NAT translations do not work until I remove and re-establish the access group on the outside interface. I'm sure there is an ordering problem on reboot but I can't figure out why. My configs are listed:

  ip inspect name Internet-out icmp router-traffic
  ip inspect name Internet-out tcp router-traffic
  ip inspect name Internet-out udp router-traffic

Outside interface config:

interface GigabitEthernet2
ip address dhcp
ip access-group Internet in
no ip unreachables
ip inspect Internet-out out
ip nat outside
ip virtual-reassembly in
duplex auto
speed auto
no cdp enable

Access group causing the issue:

ip access-list extended Internet
permit udp any any eq domain log
permit tcp any any eq domain log
permit tcp any any eq www log
permit tcp any any eq 443 log 
deny ip any any log

After a reboot - I have to manually do the following otherwise no inside NAT translations work -"show ip nat translations" shows nothing in the table.

interface GigabitEthernet2
no ip access-group Internet in
ip access-group Internet in

And like magic it all starts working. I've checked the running-config order and it is exactly the same after I issue the command to when it reboots. I'm stumped and can't figure this out.

1 Answer 1


After upgrading IOS from 15.5 to 15.5.3 I was finally able to use ZBF instead of CBAC. Because of bugs in that version you could not create policies. I was then able to remove the inspect rules and substitute them for policies and also remove the access-lists. Since making these changes, the issues on reboot and the router hanging problems (yes the outside interface would hang after 4-5 hours) have gone away completely.

It appears that there are some serious bugs in CBAC for newer IOS versions and Cisco is not going to fix them according to their own documentation. My advice is to ditch CBAC and go for Zone Based Firewall in all newer IOS versions.

  • You should verify which 15.5(3) version you are running. 15.5(3)M1 will reboot itself on a regular time period. This is supposed to be fixed in 15.5(3)M3.
    – Ron Maupin
    Commented Feb 8, 2016 at 4:12
  • The version is: Cisco IOS Software, C860 Software (C860VAEW-ADVSECURITYK9-M), Version 15.5(3)M, RELEASE SOFTWARE (fc1) Commented Feb 8, 2016 at 4:35
  • 3 days without a reboot so far - it would be nice to know if my version doesn't have the bug @RonMaupin mentioned. If anyone can help it would be appreciated. Commented Feb 9, 2016 at 11:55
  • 1
    I think it was something like every 17 days, but I don't remember exactly. You can ask Cisco about it.
    – Ron Maupin
    Commented Feb 9, 2016 at 12:00
  • 1
    As far as I know, that code should be fine. You can always discuss bugs with Cisco.
    – Ron Maupin
    Commented Feb 12, 2016 at 5:18

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