Configure the router's name, map the name to an IP address and alias, and configure a sysid:
[edit] user@host#set system host-name router-sj1[edit] user@host#set system static-host-mapping router-sj1 inet 192.168.1.77[edit] user@host#set system static-host-mapping router-sj1 alias sj1[edit] user@host#set system static-host-mapping router-sj1 sysid 1921.6800.1077[edit] user@host#showsystem { host-name router-sj1; static-host-mapping { router-sj1 { inet 192.168.1.77; alias sj1; sysid 1921.6800.1077; } } }