Both running in version 12.1.3.2. I can ssh to mgmt IP using root account. If I ssh to external IP of existing GTM, it was failed. I have try telnet port 22 from outside to external IP of existing GTM and run tcpdump. Below are the output.
[root@GTM:Active:Standalone] config tcpdump -nni 1.1 -vv host X.X.Y.Y and port 22
tcpdump: listening on 1.1, link-type EN10MB (Ethernet), capture size 65535 bytes
17:48:40.688104 IP (tos 0x0, ttl 121, id 4122, offset 0, flags [DF], proto TCP (6), length 52)
210.195.27.234.63179 > X.X.Y.Y.22: Flags [S], cksum 0x9dcc (correct), seq 3434528005, win 17520, options [mss 1440,nop,wscale 8,nop,nop,sackOK], length 0 in slot1/tmm0 lis=
17:48:43.688044 IP (tos 0x0, ttl 121, id 4123, offset 0, flags [DF], proto TCP (6), length 52)
210.195.27.234.63179 > X.X.Y.Y.22: Flags [S], cksum 0x9dcc (correct), seq 3434528005, win 17520, options [mss 1440,nop,wscale 8,nop,nop,sackOK], length 0 in slot1/tmm0 lis=
17:48:49.688832 IP (tos 0x0, ttl 121, id 4124, offset 0, flags [DF], proto TCP (6), length 52)
210.195.27.234.63179 > X.X.Y.Y.22: Flags [S], cksum 0x9dcc (correct), seq 3434528005, win 17520, options [mss 1440,nop,wscale 8,nop,nop,sackOK], length 0 in slot1/tmm0 lis=
^C
3 packets captured
3 packets received by filter
0 packets dropped by kernel