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Example: Configuring Multiple Routing Instances of OSPF

Figure 5 shows how you can use multiple routing instances of OSPF or OSPFv3 to segregate prefixes within a large network. The network consists of three administrative entities: voice_policy, other_policy, and the default routing instance. Each entity is composed of several geographically separate sites that are connected by the backbone and managed by the backbone entity.

Figure 5: Configuration for Multiple Routing Instances

Image h1460.gif

Sites A and D belong to the voice_policy routing instance. Sites B and C belong to the other_policy instance. Router 1 and Router 3 at the edge of the backbone connect the routing instances. Each runs a separate OSPF or OSPFv3 instance (one per entity).

Router 1 runs three OSPF or OSPFv3 instances: one each for Site A (voice_policy), Site C (other_policy), and the backbone, otherwise known as the default instance. Router 3 also runs three OSPF or OSPFv3 instances: one each for Site B (other_policy), Site D (voice_policy), and the backbone (default instance).

When Router 1 runs the OSPF or OSPFv3 instances, the following occur:

Routes from the default instance routing table are placed in the voice_policy and other_policy instance routing tables.
Routes from the voice_policy routing instance are placed in the default instance routing table.
Routes from the other_policy routing instance are placed in the default instance routing table.
Routes from the voice_policy routing instance do not enter the other_policy instance routing table.
Routes from the other_policy routing instance do not enter the voice_policy instance routing table.

Configuring Router 1

The following sections describe how to configure Router 1 in the backbone entity with multiple routing instances.

Configure the routing instances for voice-policy and other-policy:



[edit]
routing-instances {


voice-policy {
interface so-2/2/2.0;


protocols {


(ospf | ospf3) {
rib-group voice_to_inet;   # Places routes into inet.0
#


area 0.0.0.0 {
interface so-2/2/2.0;
}


}


}


}


}
other-policy {
interface so-4/2/2.0;


protocols {


(ospf | ospf3) {
rib-group other_to_inet; # Places routes into inet.0 #


area 0.0.0.0 {
interface so-4/2/2.0;
}


}


}


}

Configure the routing table group inet_to_voice_and_others to take routes from inet.0 (default routing table) and place them in the voice-policy.inet.0 and other-policy.inet.0 routing tables:



[edit]
routing-options {


rib-groups {


inet_to_voice_and_other {
import-rib [ inet.0 voice-policy.inet.0 other-policy.inet.0
];
}


}


}

Configure the routing table group voice_to_inet to take routes from voice-policy.inet.0 and place them in the inet.0 default routing table:



[edit]
routing-options {


rib-groups {


voice_to_inet {
import-rib [ inet.0 voice-policy.inet.0 ];
}


}


}

Configure the routing table group other_to_inet to take routes from other-policy.inet.0 and place them in the inet.0 default routing table:



[edit]
routing-options {


rib-groups {


other_to_inet {
import-rib [ inet.0 other-policy.inet.0 ];
}


}


}

Configure the default OSPF or OSPFv3 instance:



[edit]
protocols {


(ospf | ospf3) {


rib-group inet_to_voice_and_other; # Place prefixes from
inet.0 into


area 0.0.0.0 { # voice-policy.inet.0 and
interface so-2/2/2.0 ;# other-policy.inet.0
interface so-4/2/2.0;
}


}


}


}

Configuring Router 3

The configuration for Router 3 is the same as for Router 1 except that the interface names might differ. In this topology, the interface so-5/2/2.0 belongs to other-policy, and so-3/2/2.0 belongs to voice-policy.

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