3Com S7906E - Switch, Руководство по настройке

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If a router connects to a PE router in the same area and establishes an internal route (backdoor route) to
a destination, in this case, since an OSPF intraarea route has a higher priority than a backbone route,
VPN traffic will always travel on the backdoor route rather than the backbone route. To avoid this, an
unnumbered sham link can be configured between PE routers, connecting the router to another PE
router via an intraarea route with a lower cost.
For sham link configuration, refer to MPLS L3VPN Configuration in the MPLS Volume .
BFD
For more information about BFD, refer to BFD Configuration in the High Availability Volume .
Bidirectional forwarding detection (BFD) provides a single mechanism to quickly detect and monitor the
connectivity of links between OSPF neighbors, thus reducing network convergence time.
Protocols and Standards
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RFC 1765: OSPF Database Overflow
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RFC 2328: OSPF Version 2
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RFC 3101: OSPF Not-So-Stubby Area (NSSA) Option
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RFC 3137: OSPF Stub Router Advertisement
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RFC 3630: Traffic Engineering Extensions to OSPF Version 2
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RFC 4811: OSPF Out-of-Band LSDB Resynchronization
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RFC 4812: OSPF Restart Signaling
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RFC 4813: OSPF Link-Local Signaling
OSPF Configuration Task List
An OSPF routing domain has different types of routers, such as intra-area routers, ABR, and ASBR.
OSPF can work normally only after being enabled on a router, regardless of the router’s type. On an
OSPF-enabled router, you can use the default values of parameters, such as the transmit interval of
OSPF packets, LSA delay timer, and SPF calculation interval, or configure them as required.
Network planning is needed before OSPF configuration on routers. The configurations for routers in an
area are performed on the area basis. Wrong configurations may cause communication failures, even
routing information block or routing loops between neighboring routers..
Complete the following tasks to configure OSPF: