Multiple IP addresses on one NIC and Multiple internet connections on one nic

isp isps nic ip alias ip aliasing multiple ips on one nic

Multiple Connections to the Internet / two isps on one nic

/etc/shorewall/interfaces

net     eth0    82.94.91.79,188.204.140.224 routeback

/etc/postfix/main.cf

add 188.204.140.192/27 to mynetworks

/etc/iproute2/rt_tables

#
# reserved values
#
255     local
254     main
253     default
0       unspec
#
# local
#
#1      inr.ruhep
82 sdsl
188 fibre

ip addr add 188.204.140.196/27 brd 188.204.140.223 dev eth0:1 label eth0:1

ip route add 82.94.91.64/28 dev eth0 src 82.94.91.77 table sdsl
ip route add default via 82.94.91.65 table sdsl
ip rule add from 82.94.91.64/28 table sdsl

ip route add 188.204.140.192/27 dev eth0 src 188.204.140.196 table fibre
ip route add default via 188.204.140.193 table fibre
ip rule add from 188.204.140.192/27 table fibre

to check:
ip rule show
ip route list table fibre
ip route list table sdsl

or in /etc/network/interfaces

auto eth0
iface eth0 inet static
        address 82.94.91.77
        netmask 255.255.255.240
        #netmask 255.255.255.255
        network 82.94.91.64
        broadcast 82.94.91.79
        gateway 82.94.91.65
        dns-nameservers 213.75.63.36 194.109.9.99 212.61.33.42 194.109.6.66
        post-up ip route add 82.94.91.64/28 dev eth0 src 82.94.91.77 table sdsl
        post-up ip route add default via 82.94.91.65 table sdsl
        post-up ip rule add from 82.94.91.64/28 table sdsl

        post-down ip rule del from 82.94.91.64/28 table sdsl

        post-up ip addr add 188.204.140.196/27 brd 188.204.140.223 dev eth0:1 label eth0:1
        post-up ip route add 188.204.140.192/27 dev eth0 src 188.204.140.196 table fibre
        post-up ip route add default via 188.204.140.193 table fibre
        post-up ip rule add from 188.204.140.192/27 table fibre

        post-down ip rule del from 188.204.140.192/27 table fibre
        post-down ip addr del 188.204.140.196 dev eth0:1

To change the default gateway the server and programmes launched from it use, you may have to delete the old gateway (it'll only accept one) with

ip route del default via 82.94.91.65

and add the new one with

ip route add default via 188.204.140.193

More information:

http://linux-ip.net/html/adv-multi-internet.html#ex-adv-multi-internet-outbound-ip-routing

http://www.policyrouting.org/iproute2.doc.html#ss9.5

---

ip address management with ip addr - http://linux-ip.net/html/tools-ip-address.html#tb-tools-ip-addr-scope

ip addr add 188.204.140.195/27 brd 188.204.140.223 dev eth1 label eth1:1

A lot on policy routing - http://www.policyrouting.org/iproute2.doc.html#ss9.5

ip link list - shows the physical devices

ip addr list - shows the adressees the links have

ip addr show dev eth0

Basic ip route - http://linux-ip.net/html/tools-ip-route.html

ip route list - like netstat -rn

/etc/iproute2/rt_tables - contains the routing tables

ip route show table local / main - shows the specified table

ip -s route show cache

ip route flush cache

NB - ip route flush kills all the routing tables!!!

More on routing tables - http://linux-ip.net/html/routing-tables.html

eth0 82.94.91.77

eth0:0 188.204.140.196/27