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Dealing with Routes within a Junos OS Based Router

When migrating services from one network design to the next, it is highly likely that a non-negligible transition period is required. During this time, services may live in two worlds, in which some applications and network sites for those services are partially duplicated to allow the old and new designs to coexist.

From the perspective of an IP network, a service is identified by different abstractions, and a valid concept for a service is a set of IP addresses that are reachable from different network sites. This reachability information, which is exchanged via routing protocols, is collected in routing tables, and the best routing information from routing tables is propagated to the forwarding engine.

This chapter focuses primarily on routing and addressing for the Internet Protocol ver­sion 4 (IPv4) and illustrates Junos® operating system (Junos OS) configuration options that can leverage and optimize route manipulation among different routing tables. The underlying concepts presented only for IPv4 here can be generalized to other address families.

1.1 Route Handling Features inside a Junos OS Based Router

Transition scenarios should avoid non-standard routing-protocol behavior, unless a network designer is deliberately planning a migration considering this. The impact of a migration can be reduced by employing specific and often creative behaviors on the routers themselves, behaviors that do not change the expected routing-protocol ...

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