I attempted to add a secondary IP to a bridged remote device and left off the /24. Mac server is disabled. From the local device, I can see the IP sending broadcast packets (255.255.255.255). Winbox sees the IP address. But, when assigning an ip on the proper subdomain, I cannot connect. I cannot connect to the original primary ip address (not certain why -- perhaps assigned to the local eth instead of the bridge). Traffic is passing the link.

I attempted putting in a gateway of the device (.146 address) without success.
I can ping the MAC but not the IP (through winbox).
I attempted to add an ARP entry to the original IP, and I get a reply from the new IP saying host unreachable.

Is there any way to connect to this device without physically going to the location and plugging in directly? Disconnecting them will take down a large organization, including their phone system...

Have you tried doing a MAC-telnet from a Routerboard in the same Layer2 network?

Good suggestion. I tried it from the same RouterOS device without success.

Is there a weird route I could add, or a way to send a command from one RouterOS to another?