3Com corebuilder 3500 Implementation Manual page 368

Hide thumbs Also See for corebuilder 3500:

Table of Contents

Routing Packets

A packet's source and destination determine the routers that move it:

Intraarea — When a packet's source and destination are in the same

area, the packet is routed using internal router databases. No routers

are used outside the area.

Interarea — When a packet's source and destination are in different

areas, the topology databases in the backbone area dictate the paths

that are taken between areas.

You can use virtual links to influence the routes that are taken for

interarea traffic. See "Virtual Links" later in this chapter.

To a stub area — When a packet's destination is in a stub area (an

area that does not accept external route advertisements), OSPF uses

the area's predefined default route. You configure default routing in

area border routers that serve an OSPF stub area, such as area border

router 1 in Figure 70. For more information, see "Stub Default

Metrics" later in this chapter.

To a different autonomous system — When a packet's source and

destination are in different autonomous systems, ASBRs compute the

routing paths using data obtained from another protocol, such as the

Border Gateway Protocol. The boundary routers flood these external

routes throughout all areas in the autonomous system except stub