Last week I had a problem with a wifi AP dropping off the network intermittently. While I investigated this I used the 'Topology' view of the 2860n (the 'Splodge' button at the top of the dashboard) to see how the router was configured. This usually brings up a visual map of the network, but this time the web GUI froze and the router crashed. Power cycling the router brings up the login windows, but once logged in the dashboard is only partially displayed, and the router crashes again. I tried reflashing the firmware using TFTP (with both 3.9.1 which was installed a few weeks ago and the previous version) the GUI was not accessible. Pressing and holding the reset button did not reset the router to factory, so a recent config was loaded onto a replacement router to recover the situation. I have since found the reset button will restore to factory, but only if it is pressed before logging in to the router.

Subsequently I have found that the replacement router (another 2860) and a 2862 lock up in the same way if the 'Topology' button is pressed.

By trial and error I have found that the issue seems to be related to enabling the LAN 'DMZ' feature. Taking a factory reset router and enabling the DMZ port (selecting 'LAN/General Setup/DMZ Port/Status') is the single setup change which will cause the topology button the crash the 2860.

The router can be recovered (without a factory reset) from a telnet/SSH command prompt by turning off the DMZ port using command 'msubnet switch dmz off' followed by 'sys reboot'. (While the DMZ port is turned on LAN port 1 of the 2860 will default to the DMZ subnet of 192.168.7.0/24 (LAN port 4 of the 2862), so use port 2 for the telnet/SSH connection.)

I have tried a few version of 2860 firmware:
3.7.8.1 - No topology button
3.8.4.3 - Has topology button. Turn on DMZ - Doesn't crash
3.8.8 - Has topology button. Turn on DMZ - Crashes
3.9.1 - Has topology button. Turn on DMZ - Crashes

The DMZ port feature seems to be working as expected in our fully configured routers.

I'm mainly posting to remind myself how to recover from this situation if I see it again, but can anyone advise how to prevent this router crash (other than not using the topology button)?

Regards, Neil