Notes on a crashing Apple Internet Router / Apple IP Gateway

[cheesestraws]

tl;dr: resolving an IP address conflict can cause Apple IP Gateway to go into some kind of infinite loop and crash. If you must run IP Gateway, keep the IP ranges used for MacIP and normal allocations disjoint; better still, use macipgw.

Apparent Symptoms:

1. I rebooted my virtual machine server.
   
   
2. My AppleTalk router started crashing when plugged into Ethernet. If only LocalTalk was plugged in, no crash.
   
   
3. Before it crashed, Port Statistics showed one packet per second being sent out of the LocalTalk port, but only when Ethernet was plugged in.

Aetiology:

1. I thought I had disabled Apple IP Gateway. I had not in fact done so.
   • It is possible for IP Gateway to be running without really being at all visible in the UI; check your Extensions folder.
     
2. I had created a virtual machine on the VM server with the same IP address that IP gateway was trying to use, because of a record-keeping failure. I left that VM running for a long time by accident.
   
   
3. When I rebooted the VM server, that virtual machine did not restart, and the IP conflict went away.

What happened next?

1. Apple IP Gateway started spamming IPADDRESS NBP lookups out of the LocalTalk interface for the lately conflicted IP address.
   
   
2. After a minute or so (I suspect 256 packets?) it crashed.
   
   
3. Attempting to stop the IP Gateway through the IP Gateway Manager application also crashed. IP Gateway Manager showed the IP as a conflict, even though it was no longer a conflict.
   
   
4. This persisted across reboots.

What did I do about it?

1. Removed Apple IP Gateway from extensions folder.
   
   
2. Went back to bed.

 

[Durosity]

Went back to bed.

As I recall that was Apple’s official guidance to resolve this issue.