I've configured the management interface on our ASA 5550. The address is 192.168.254.5 and it's next hop is .1 (vlan 254 on 3750).
I can ping the management interface fine from my laptop (10.128.100.75), but I can't telnet to the device on the management interface and it gives the following error:
%ASA-6-110003: Routing failed to locate next hop for TCP from management:192.168.254.5/23 to management:John-Blakley/2223
I can't add the route as "route management 10.128.100.0 255.255.255.0 192.168.254.1" because it says that it overlaps with an existing route. The 10.128.100.0 subnet will be exiting out of the inside interface.
I'm not sure if this is workable in your situation but if your IT department works on a particular subnet that's smaller than the 10.128.100.0/24 subnet you could put that in to exit the management interface.
We had a similar problem with setting up our management interface on our ASA recently. We have a route through the inside interface that was for 10.0.0.0/8 but we were also able to put in a smaller subnet (10.10.5.0/28) to exit the management interface just for the IT department. It might be a good idea to define a route for a smaller subnet to the IT department anyways as a security precaution.
This worked for us and then traffic that went in the management interface knew how to get back out. I didn't get the exact error you got but then I didn't try to telnet to the ASA. Let me know if this works for you. :)
We have configured the outside and inside Interface with official ipv6 adresses, set a default route on outside Interface to our router, we also have definied a rule , which also gets hits, to permit tcp from inside Interface to any6.
In Syslog I also se...