On a traditional IP network, only one unicast topology exists, and only one unicast forwarding table is available on the forwarding plane, which forces services transmitted from one router to the same destination address to share the same next hop, and various end-to-end services, such as voice and data services, to share the same physical links. As a result, some links may become heavily congested whereas others remain relatively idle. To address this problem, configure multi-topology to divide a physical network into different logical topologies for different services.
By default, the base topology is created on the public network. The class-specific topology can be added or deleted in the public network address family view. Each topology contains its own routing table. The class-specific topology supports the addition, deletion, and import of protocol routes.
The base topology cannot be deleted.
Direct routes can be added to or deleted from the routing table of any topology. The same routes can also be added to multiple topologies, independent of each other.
Direct routes associated with interfaces are added to the base topology by default. Direct routes in the base topology are not deleted, and the base topology contains all direct routes.
Static routes can be added to or deleted from the routing table of any topology. The routes with the same prefix, outbound interface, and next hop can also be added to multiple topologies, independent of each other.
Static routes, by default, are configured in the base topology. However, they can be configured in a specified class-specific topology and can be changed or deleted.
Static routes have no outbound interfaces, and therefore, need to perform recursion based on the next hop. In this case, you cannot specify the topology in which the next hop resides.
Public network static route recursion to a VPN next hop or VPN static route recursion to a public network next hop can be configured only in the base topology. When configuring static routes, you cannot specify the name of the topology in which the destination resides.