vagrant@manager:~$ ip a 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 08:00:27:06:38:eb brd ff:ff:ff:ff:ff:ff inet 10.0.2.15/24 brd 10.0.2.255 scope global dynamic eth0 valid_lft 84465sec preferred_lft 84465sec inet6 fe80::a00:27ff:fe06:38eb/64 scope link valid_lft forever preferred_lft forever 3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 08:00:27:39:27:f1 brd ff:ff:ff:ff:ff:ff inet 192.168.56.7/24 brd 192.168.56.255 scope global dynamic eth1 valid_lft 465sec preferred_lft 465sec inet6 fe80::a00:27ff:fe39:27f1/64 scope link valid_lft forever preferred_lft forever

this generated: docker swarm join --token SWMTKN-1-35q9xg25chynpxgljdyzd65yjggbe38s5j3kydto6vp6m341fk-cisjtrbdk3mtwgcgxrdywdeng 10.0.2.15:2377 --advertise-addr 10.0.2.15

error: Error response from daemon: rpc error: code = Unavailable desc = all SubConns are in TransientFailure, latest connection error: connection error: desc = "transport: Error while dialing dial tcp 10.0.2.15:2377: connect: connection refused"

so i changed the 10.0.2.15:2377(eth0) to 192.168.56.7(eth1) ip address and tried to connect it as:

docker swarm join --token SWMTKN-1-35q9xg25chynpxgljdyzd65yjggbe38s5j3kydto6vp6m341fk-cisjtrbdk3mtwgcgxrdywdeng 192.168.56.7:2377 --ad vertise-addr 10.0.2.15

and connection became success.

seems like the manager node eth0 ip address didn't worked out for swarn node connectivity.