Linux network is unreachable

route: SIOCADDRT: Network is unreachable

[root@vm50 ~]# nmcli connection show //查看网卡

eth0 4f5f8b5d-4b51-4e1c-98c7-40f0eb90f241 802-3-ethernet eth0
virbr0 566dccb2-cbb0-4bbe-a714-06f3d313d9cd bridge virbr0
[root@vm50 ~]# nmcli connection add con-name eth1 type ethernet ifname eth1   //添加网卡
连接“eth1”(4cb9f43e-77d6-455f-990c-620e4a12d52b) 已成功添加。

[root@vm50 ~]# nmcli connection modify eth1 ipv4.method manual  ipv4.addresses 192.168.2.50/24 con.autoconnect yes  // 配置ip地址，此处192.168.2.50/24（24未加，则网络不可达）
[root@vm50 ~]# nmcli connection up eth1    /激活网卡
连接已成功激活（D-Bus 活动路径：/org/freedesktop/NetworkManager/ActiveConnection/8）
[root@vm50 ~]# nmcli connection show
名称    UUID                                  类型            设备   
eht1    4cb9f43e-77d6-455f-990c-620e4a12d52b  802-3-ethernet  eth1          //已经添加的网卡
eth0    4f5f8b5d-4b51-4e1c-98c7-40f0eb90f241  802-3-ethernet  eth0   
virbr0  566dccb2-cbb0-4bbe-a714-06f3d313d9cd  bridge          virbr0

[root@mysql51 ~]# systemctl stop NetworkManager    //配置网关，需先停止网络管理   
[root@mysql51 ~]# route -n                  //查看网关Gateway       
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.4.0     0.0.0.0         255.255.255.0   U     100    0        0 eth0
192.168.122.0   0.0.0.0         255.255.255.0   U     0      0        0 virbr0
[root@mysql51 ~]# route add default gw 192.168.4.50                 
    route: SIOCADDRT: Network is unreachable    //配置网关，出现网络不可达，重新配置ip
[root@mysql51 ~]# route add default gw 192.168.4.50
[root@mysql51 ~]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.4.50    0.0.0.0         UG    0      0        0 eth0       
192.168.4.0     0.0.0.0         255.255.255.0   U     100    0        0 eth0
192.168.122.0   0.0.0.0         255.255.255.0   U     0      0        0 virbr0