A route domain is a configuration object that isolates network traffic for a particular application on the network.
Because route domains segment network traffic, you can assign the same IP address or subnet to multiple nodes on a network, provided that each instance of the IP address resides in a separate routing domain.
Using the route domains feature of the BIG-IP system, you can provide hosting service for multiple customers by isolating each type of application traffic within a defined address space on the network.
With route domains, you can also use duplicate IP addresses on the network, provided that each of the duplicate addresses resides in a separate route domain and is isolated on the network through a separate VLAN. For example, if you are processing traffic for two different customers, you can create two separate route domains. The same node address (such as 10.0.10.1) can reside in each route domain, in the same pool or in different pools, and you can assign a different monitor to each of the two corresponding pool members.
A route domain ID is a unique numerical identifier for a route-domain. You can assign objects with IP addresses (such as self IP addresses, virtual addresses, pool members, and gateway addresses) to a route domain by appending the %ID to the IP address.
The format required for specifying a route domain ID in an object’s IP address is A.B.C.D%ID, where ID is the ID of the relevant route domain. For example, both the local traffic node object 10.10.10.30%2 and the pool member 10.10.10.30%2:80 pertain to route domain 2.
The BIG-IP system includes a default route domain with an ID of 0. If you do not explicitly create any route domains, all routes on the system pertain to route domain 0.
Forwarding of traffic between route domains is by default enabled between route domains in a parent-child relationship only. (That is, traffic received in a child route domain can be forwarded to a parent route domain and the reverse.) Consequently, by default, the BIG-IP system does not load balance traffic arriving in route domain 1 to servers in any other route domain, except for the parent route domain.
You can control this behavior by configuring the Strict Isolation feature of a route domain. For example, to allow traffic forwarding between route domains 1 and 2, (without making route domain 2 a parent of route domain 1 or route domain 1 a parent of route domain 2), you must disable the Strict Isolation property on both route domains.
Each route domain can have a parent route domain, identified with a parent ID. The parent ID identifies another route domain on the system that the system can search to find a route.
For example, suppose you create route domain 1 with a parent ID of 0. For traffic pertaining to route domain 1, the system looks within route domain 1 for a route for the specified destination. If no route is found, the system searches the routes in route domain 0.
If the system finds no route in the parent route domain, the system searches the parent route domain’s parent, and so on, until the system finds either a match or a route domain with no parent. In the latter case, the system refrains from searching any other route domains to find a match, thus preventing the system from using a route from another route domain.
You can assign one or more VLANs, VLAN groups, or tunnels to a route domain. The VLANs, VLAN groups, or tunnels that you assign to a route domain are those pertaining to the particular traffic that you want to isolate in that route domain. Each VLAN, VLAN group, or tunnel can be a member of one route domain only.
When you assign a VLAN group to a route domain, the BIG-IP system automatically assigns the VLAN group members to the route domain.
Please note the following facts:
For each route domain that you configure, you can enable one or more dynamic routing protocols. Use of dynamic routing for route domain 0 or any other route domain is optional.
The route domains feature includes the concept of default route domains, to minimize the need for you to specify the %ID notation. When you designate a route domain as the default route domain in a partition, any BIG-IP system objects in that partition that do not include the %ID notation in their IP addresses are automatically associated with the default route domain.
The BIG-IP system, by default, includes one route domain, named route domain 0. Route domain 0 is known as the default route domain on the BIG-IP system, and this route domain resides in administrative partition Common. If you do not create any other route domains on the system, all traffic automatically pertains to route domain 0.
If you want to segment traffic into multiple route domains, you can create additional route domains in partition Common and then segment application traffic among those route domains. Any BIG-IP addresses that do not include the route domain ID notation are automatically associated with the default route domain.
For administrative partitions other than Common, you can create a route domain and designate it as a partition default route domain. A partition can contain one partition default route domain only.
The benefit of having a partition default route domain is that when you create objects such as a virtual server and pool members within that partition, you do not need to specify the ID of that default route domain within the addresses for those objects. For example, if you create a partition default route domain with an ID of 2 in partition A, the system automatically assigns any partition A object IP addresses without a route domain ID to route domain 2.
If no partition default route domain exists within the partition, the system associates those addresses with route domain 0 in partition Common.