Shulou(Shulou.com)06/01 Report--

OSPF introduces the technology of region division, and OSPF can divide the whole AS into several small regions. Area0 defaults to the backbone area, and the rest is the standard area.

In the OSPF area, the router is divided into internal router (IR), interarea router (ABR) and autonomous system boundary router (ASBR).

In the OSPF area, advertisements (LSA) are divided into seven categories of announcements (LSA):

V LSA1: internal route advertises route description and propagates all routes in the range area.

V LSA2: internal routes advertise routing entries and propagate all routes in the range area.

V LSA3: interarea routes advertise routing entries that propagate the entire AS autonomous system.

V LSA4: the boundary area routes the location of the ASBR, and the propagation range is the area where the ASBR is located.

V LSA5: external routing entry, propagating for the entire AS autonomous system. E1: cost cumulative E2: fixed cost 20.

V LSA7: external routing entry, propagating for the entire AS autonomous system.

Note: LSA7 is the routing entry propagated in the optimized region NSSA area.

The role of regional optimization: reduce the number of routing entries and improve routing efficiency.

Regional optimization:

V stub area: optimize for non-backbone and non-ASBR areas and replace it with a default route to prevent LSA5 type advertisements.

V complete stub area: optimize for non-backbone and non-ASBR areas and replace it with a default route to prevent LSA3,4,5 type advertisements.

V NSSA area: optimize the area where the ASBR boundary route is located, and convert LSA4,5 class advertisements into LSA7 class advertisements, which can reduce routing entries and resource consumption problems.

Identity: LSA1:O LSA3:OIA LSA5:0 E1/E2 stub area default route: O*IA

Redistribut route redistribution technology: two AS autonomous systems use different routing protocols. In order to learn the routing of another autonomous system, we need to use route redistribution technology.

The idea of Redistribut route redistribution:

V determine the routing protocol used by the autonomous system

V determine the location of the ASBR

V determines the direction of route redistribution.

Type of route: OSPF,RIP, directly connected route (Conncet), static route (static), default route (default).

Note: because RIP has a limit of 15 hops, you need to specify a metric metric in the OSPF import RIP protocol.

OSPF routing address summarization technology: aggregates a small range of IP addresses into a large range of IP addresses.

Advantages of OSPF summary technology:

V reduce routing entries

V shielding some details of network instability to save resources

V saves resources by reducing flooded LSA

OSPF route summary sub-area route summary and external route summary.

V Interarea route summary: route IP addresses planned for each area are summarized into one large address.

V external route summary: summarize the learned external route IP address into one large address.

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