route

hi,
netstat -rn
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
0.0.0.0 192.168.30.2 0.0.0.0 UG 0 0 0 ens33
169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 ens33
169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 ens37
192.168.30.0 0.0.0.0 255.255.255.0 U 0 0 0 ens33
192.168.50.0 0.0.0.0 255.255.255.255 UH 0 0 0 ens33

I like to know what mean 0.0.0.0 in Gateway column.
this is a router with ens33-192.168.30.128 and ens37-192.168.50.1 and ipforward is set.
ping 192.168.50.5 (other server) work.ssh user@192.168.50.5 not work.
from 192.168.50.5 -ssh user@192.168.30.128 work.
there are no iptables rule on both servers.
tnx