How to route outgoing requests through a second IP on the server?

Question

ubuntu

Good day.
There is a server on ubuntu, the server has two external IPs (1.1.1.1 and 2.2.2.2)
in /etc/network/interfaces like this:

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet static
  address 1.1.1.1
  netmask 255.255.255.0
  network 1.1.1.0
  broadcast 1.1.1.255
  gateway 1.1.1.254
  post-up /sbin/ifconfig eth0:1 2.2.2.2 netmask 255.255.255.0 broadcast 2.2.2.2
  post-down /sbin/ifconfig eth0:1 down

How to make outgoing requests to a certain resource (3.3.3.3) through the second IP?
Or am I asking garbage and for an external resource all requests will go in any case from the same gw ?

Answer 1

You need to add the appropriate route:
askubuntu.com/a/252699 It is
better to configure the second address not through post-up, but with a separate rule:

auto eth0
iface eth0 inet static
  address 1.1.1.1
  netmask 255.255.255.0
  gateway 1.1.1.254

auto eth0:1
iface eth0:1 inet static
  address 2.2.2.2
  netmask 255.255.255.0
  up ip route add 3.3.3.3 dev eth0 src 2.2.2.2 via 2.2.2.254 || true
  down ip route del 3.3.3.3 || true

wiki.debian.org/NetworkConfiguration#Legacy_method