linux: how to set multiple (public) IP to one network interface? (For Ubuntu 22.04 / 14.04)
There are guides about netplan or /etc/network/interfaces, but they only tells to add IP to interfaces file or netplan YAML.
But it does not actually work – IP appears locally, but routing does not work.
(“ping -I new-IP ” on the machine, or “ping new-IP” from other machine does not pass at all.)
What configuration should I do to make it actually work?
For example:
- Let default/primary IP range be 80.80.80.80/29.
- Let new IP be 110.110.110.110/32.
# primary IP config (14.04/interfaces; 22.04/netplan is similar and skipped)
auto eth1
iface eth1 inet static
address 80.80.80.82
netmask 255.255.255.248
gateway 80.80.80.81
auto eth1:0
iface eth1:0 inet static
address 80.80.80.83
netmask 255.255.255.248
...
# ip route show
default via 80.80.80.81 dev eth1
80.80.80.80/29 dev eth1 proto kernel scope link src 80.80.80.82
172.16.0.0/12 via 172.16.xx.yy dev eth0
# The only eth1 route entry is 1st line.
Which netmask/gateway should I set?
What routing config should I add?
