Is MikroTik compatible with ShoreTel PBX? I have setup a simple router setup with two RB2011LS-IN routers with the fiber cards. I have a different subnet/network on each router. I can get all traffic (web, other network devices, internal and external websites, etc.) to work on these routers. The issue that I am having is when a phone is registered with the ShoreTel server through the two routers, it registers and comes up for a few seconds and then drops searching for service. Then the phone will reconnect for a few seconds and repeat the drop/cycle.

I don't know neither use Shoretel pbx, but if it uses sip (as 99% of ip pbx) I think there should be no problem.
If it uses custom ports for sip add them to ip firewall service-port

it uses all services of sip...as far as i know