The Mikrotik config segment prints are:
admin@rtehckp001] /ip firewall nat> print
Flags: X - disabled, I - invalid, D - dynamic
[admin@rtehckp001] /ip route> print
Flags: X - disabled, A - active, D - dynamic,
C - connect, S - static, r - rip, b - bgp, o - ospf, m - mme,
B - blackhole, U - unreachable, P - prohibit
# DST-ADDRESS PREF-SRC GATEWAY-STATE GATEWAY DISTANCE INTERFACE
0 A S 0.0.0.0/0 reachable 192.168.102.253 1 ether1
reachable ether1 ether1
1 ADC 172.17.191.0/24 172.17.191.253 0 Colo Private
2 ADC 192.168.100.0/24 192.168.100.253 0 ether3
3 ADC 192.168.102.0/24 192.168.102.252 0 ether1
4 A S 192.168.200.0/24 reachable 192.168.100.254 1 ether3
reachable ether3 ether3
So the NAT table is blank and the routes are what I expect.
Yes the Sonicwall does have a static route back to the 192.168.100.0 subnet so it knows where my workstation lives. I have always been able to ping the Sonicwall from my workstation.
I should also have mentioned that performing a ping or tracert on the Mikrotik (WinBox) it also tried to use the 192.168.102.254 (Telstra Cisco) as the default route most of the time, not always, occasionally it also went the via the correct gateway.
But I have fixed the problem, apparently. Last night whilst researching the v4.5 upgrade I noticed the mention of a bug fix for something to do with delete static routes?
When I origninally setup the Mikrotik the default route was directed to 192.168.102.254 which at that stage was the Sonicwall as the Cisco was not connected. Before I connected the Mikrotik to the production network I changed the Soincwall to .253 and EDITED the default route on the Mikrotik.
All I have done to apparently correct the problem is to DELETE the default route completely and ADD it back, no change in the actual settings. Everything now routes as expected?