Avaya ERS 8600 series, Руководство по настройке

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Figure 8: Virtual link between ABRs through a transit area
To configure a virtual link between the ABRs in Area 1 and Area 3, define Area 2 as the transit
area between the two areas. Identify R2 as the neighbor router, through which R2 must send
information to reach the backbone through R1.
Specifying ASBRs
ASBRs advertise non-OSPF routes into OSPFdomains so that they can pass through the
OSPF routing domain. A routercan function as an ASBR if one or more of the router interfaces
connectsto a non-OSPF network.
Limit the number of ASBRs in your network to conserve resources, or to specifically control
which routers perform as ASBRs to control traffic flow.
OSPF routing algorithm
A separate copy of the OSPF routing algorithm runs in each OSPF area. Routers that connect
to multiple areas run multiple copies of the algorithm. The processes governed by the routing
algorithm are as follows:
• When a router starts, it initializes the OSPF data structures and then waits for indications
from lower level protocols that the interfaces are functional.
• A router uses the Hello Protocol to discover neighbors. On point-to-point and broadcast
networks, the router dynamically detects neighbors by sending hello packets to the
IPv6 routing fundamentals
46 Configuration — IPv6 Routing November 2010