block ssh for a node ip

You could also very easily do this with packet filter rules. The iRule will allows a full three-way handshake before denying the connection while the packet filter will stop it before that.

Otherwise your iRule might look like this:

when CLIENT_ACCEPTED {
    if { [IP::addr [IP::local_addr] equals 10.xxx.xxx.xx2] and [TCP::local_port == 22] } {
        log local0. "ssh request for: [IP::local_addr] from IP: [IP::client_addr] rejected by iRule blockssh"
        reject
    } 
}