AP1131AG switches gateways

[acadia]

We have a couple dozen AP1131AG access points on campus, each running c1130-k9w7-tar.124-21a.JA1.  For several years now, we have had an intermittent issue where, after a restart due to power outage or what have you, the AP comes back up, but it has abandoned it's hardcoded gateway, and adopted a new one, presumably based on it's own IP.

For example, below is a section from the config on a typical 1131 AP on our network.

interface BVI1
ip address xxx.yyy.35.44 255.255.248.0
no ip route-cache

!

ip default-gateway xxx.yyy.32.1

Following a restart, the ip default-gateway line has changed, unprompted to

ip default-gateway xxx.yyy.35.1

Since 35.1 is not a valid IP on our router, this AP can now no longer talk to anything outside of the network infrastructure xxx.yyy.32.1 255.255.248.0 subnet.  I end up having to telnet in from an IOS switch and changing the gateway back and then saving the conf again.  This works for a few months, and then one day a restart will do this again.

Anyone seen something like this and know what to do about it?

[Serge Yasmine]

Hi, i said i'll give this a shot in my lab and i was not able to reproduce.

i used same code version as you /c1240-k9w7-mx.124-21a.JA1

interface BVI1
ip address xxx.yyy.35.44 255.255.248.0
no ip route-cache
end

ip default-gateway xxx.yyy.32.1

remained correct after a save and reload.

check couple of things:

1- show startup-config --> is the default gateway correct there?

2- any snmp activity pushing new config to the ap when it restarts?

[Tiago Antunes]

Hi,

the only this could happen is if you had previously the command:

ip default-gateway xxx.yyy.35.1

And saved the config.

Then you realized it was wrong, and changed it to

ip default-gateway xxx.yyy.32.1

However, you did not saved the config.

Now, after the reboot the IOS will check the running config saved and will populate the configu with the saved config.

So if it was last saved with the incorrect ip address, it will show up with the worng address.

Other than this there is no other way.

The IOS ap simply reads the file where the config was last saved and updates the current running config with the contents of that file.

HTH,

Tiago

--

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[acadia]

Nope, xxx.yyy.35.1 has NEVER been a valid IP on our network, and I have backed up the config of every switch and AP on our network and they all have

ip default-gateway xxx.yyy.32.1

in the saved config.  It doesn't happen on every one of our APs and it doesn't happen after every reboot.  We have a few dozen 1131AG APs floating around, all with nearly identical configs except for IP and hostnames. There's only about 4 that repeatedly have this problem, and even then only every so often. If you go into the AP when it's in this state, it shows

ip default-gateway xxx.yyy.35.1

in the show running-config, instead of the valid gateway. the IP of the AP is xxx.yyy.35.zzz 255.255.248.0, part of our infrastructure subnet which begins at xxx.yyy.32.1

I'm more or less at a loss to explain it, as they've all been updated to the aforementioned IOS version, and all share nearly identical configs.

I wonder if its possible that there's something hardware related, such as failing NVRAM, which is corrupting the startup-config, but in that case, i'd think that the affected units wouldn't all be losing the same line.

[acadia]

Resolved. Looking at the startup-config, vs the running config, turns out the startup-config told the AP to get info from DHCP rather than hard coded like the bulk of our APs.  The DHCP server is configured to give out the proper gateway, but somewhere in transit it was not applying it correctly. Hardcoded all the instances of this, admittedly silly, misconfiguration and now problem is resolved.