if you are trying to attache the new network interface for your Ubuntu 18.04 EC2 instance, this post might help you to figure out.
because of Netplan is new network manager in Ubuntu 18.04, things became different as before, and Netplan looks not supported asymmetric routing for now, that is required you to set static ip address & routes for both interfaces.
follow above situation
we have to set a default route by
network: version: 2 renderer: networkd ethernets: eth0: addresses: - 192.168.0.5/24 dhcp4: no routes: - to: 0.0.0.0/0 via: 192.168.0.1 # gateway address on-link: true - to: 0.0.0.0/0 via: 192.168.0.1 # gateway address table: 900 - to: 192.168.0.5 via: 0.0.0.0 scope: link table: 900 routing-policy: - from: 192.168.0.5 table: 900 eth1: addresses: - 192.168.1.5/24 dhcp4: no routes: - to: 0.0.0.0/0 via: 192.168.1.1 # gateway address on-link: true - to: 0.0.0.0/0 via: 192.168.1.1 # gateway address table: 999 - to: 192.168.1.5 via: 0.0.0.0 scope: link table: 999 routing-policy: - from: 192.168.1.5 table: 999
to let configurations take effect execute
netplan --debug apply
or you can use
netplan try, it will setup your configuration with rolling back mechanisms, it will rolling back your last configurations in 120 seconds