I get this error trying to add an IP / subnet address

So you're trying to add a self ip and get this error? Does it really say 'old' or did you add that?

are you adding the same selfip but different subnet mask?

are you adding the same selfip but different subnet mask?

We don't have that self IP anywhere else in the system besides the virtual server, which doesn't count towards the self IP

if you do not see that ip in gui and configuration file (in all partitions), try to force mcpd to reload the configuration. if still not working, i think you had better open a support case.

sol13030: Forcing the mcpd process to reload the BIG-IP configuration

We don't have that self IP anywhere else in the system besides the virtual server, which doesn't count towards the self IP

if you do not see that ip in gui and configuration file (in all partitions), try to force mcpd to reload the configuration. if still not working, i think you had better open a support case.

sol13030: Forcing the mcpd process to reload the BIG-IP configuration