How to add a static route to a VNX Block SP?

Hi,

I'm trying to add a host specific route to a block SP so that it can route to an ESRS gateway IP via a different gateway IP than the default gateway

The naviseccli command does not appear to have option to specify an different gateway IP

navisecscli -h ..... networkadmin ... route [-o]   [-spa|b] (default - connected SP] [-portid (default = 0)] [-vportid (default=0] ...   [-add -destination [-subnetmask | -prefixlength ] ...

So how do I add the SP equivalent of the windows command:

route -p add mask 255.255.255.255

Is there a trick using portid and vportid? I can't find any useful docs about this.

Any ideas?

Thanks

Simon