Linux Solutions

Welcome to the tutorial guide. The guide will provide a user with guidance and instructions on split access.
It is good to know that a user can set some symbolic names such as $IF1, $IF2, $IP1, etc. Let’s assume that $IF1 is the name of the first interface and $IF2 the name of the second. A user can then use $IP1 as an IP address associated with $IF1 and $IP2 the IP address associated with $IF2. Now a user can then let $P1 be the IP address of the gateway at Provider 1, and $P2 the IP address of the gateway at provider 2. Finally, let $P1_NET be the IP network $P1 is in, and $P2_NET the IP network $P2 is in.
This will result in two additional routing tables, say T1 and T2. These are added in /etc/iproute2/rt_tables. Now a user can set up routing in these tables as follows:
ip route add $P1_NET dev $IF1 src $IP1 table T1
ip route add default via $P1 table T1
ip route add $P2_NET dev $IF2 src $IP2 table T2
ip route add default via $P2 table T2

A user can just build a route to the gateway and build a default route via that gateway, as a user would do in the case of a single upstream provider, but put the routes in a separate table per provider.
Now a user can set up the main routing table. It is good to know that that the src arguments ensure the right outgoing IP address is chosen.
ip route add $P1_NET dev $IF1 src $IP1
ip route add $P2_NET dev $IF2 src $IP2

A users preference for default route is:
ip route add default via $P1

After this, a user can set up the routing rules. These actually choose what routing table to route with. Here a user has to ensure that in order to make sure that he or she routes out a given interface if a user already has the corresponding source address:
ip rule add from $IP1 table T1
ip rule add from $IP2 table T2

If a user followed advise and guidance as provided in this tutorial guide then he/she would have learnt about split access.