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Configuration Guide - IP Unicast Routing

CloudEngine 12800 and 12800E V200R002C50

This document describes the configurations of IP Unicast Routing, including IP Routing, Static Route, RIP, RIPng, OSPF, OSPFv3, IPv4 IS-IS, IPv6 IS-IS, BGP, Routing Policy, and PBR.

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Summary of OSPF Configuration Tasks

Summary of OSPF Configuration Tasks

Table 5-19 describes the OSPF configuration tasks.

Table 5-19 OSPF configuration tasks




Configuring basic ospf functions

The configuration of basic OSPF functions is the foundation of the OSPF network and the precondition for other OSPF functions.

Configuring Basic OSPF Functions

Setting Session Parameters for OSPF Neighbor or Adjacency Relationships

Configuring OSPF Attributes in Different Types of Networks

Configuring OSPF areas

  • In a stub area, the area border router (ABR) does not transmit learned autonomous system (AS) external routes. This reduces entries in the routing table on the ABR in the stub area and the amount of routing information transmitted.

  • An NSSA is a new type of OSPF areas. Neither an NSSA nor a stub area transmits routes learned from other areas in the AS where it resides. Different from a stub area, an NSSA allows AS external routes to be imported and advertised in the entire AS.

Configuring OSPF Stub Areas

Configuring OSPF NSSAs

Adjusting OSPF route selection

To meet various user requirements, you can adjust OSPF parameters to flexibly control OSPF routing.

Adjusting OSPF Route Selection

Controlling OSPF routing information

To meet network requirements, you can configure different parameters to accurately control the advertisement and receipt of OSPF routes.

Controlling OSPF Routing Information

Controlling the convergence speed of OSPF routes

To enable OSPF to quickly detect changes in the network topology, you can speed up OSPF route convergence. To decrease the impact of route flapping on the network and relieve loads on devices, you can lower the convergence speed of OSPF routes.

Configuring OSPF Fast Convergence

Improving reliability of an OSPF network

  • OSPF IP FRR pre-computes a backup link by using the Loop-Free Alternate (LFA) algorithm, and then adds both the backup and primary links to the forwarding table. In the case of failures, OSPF IP FRR can fast switch traffic to the backup link before routes on the control plane converge. This prevents traffic interruption, protects traffic, and thereby improves reliability of an OSPF network.

  • By default, on broadcast networks, the interval for sending Hello packets is 10 seconds; on NBMA networks, the interval for sending Hello packets is 30 seconds. The interval for declaring a neighbor Down, that is, the dead time after which a neighbor relationship becomes invalid, is four times the interval for sending Hello packets. If a switch does not receive a Hello packet from its neighbor within the dead time, the switch deletes the neighbor. That is, the switch detects neighbor faults at the second level. This causes a large number of packets to be lost on a high-speed network.

    Bidirectional Forwarding Detection (BFD) is introduced to solve the above problem in the existing detection mechanism. BFD ensures that the detection interval is improved to the millisecond level. Instead of replacing the Hello mechanism of OSPF, BFD works with OSPF to fast detect adjacency faults. In addition, BFD instructs OSPF to recalculate corresponding routes to ensure correct packet forwarding.

  • When a switch restarts or performs an active/standby switchover, it directly ages all routing entries in the Forward Information Base (FIB) table. This results in route interruption. In addition, neighboring switches remove this switch from the neighbor list, and notify other switches. This causes SPF re-calculation. If this switch recovers within a few seconds, the neighbor relationship becomes unstable, resulting in route flapping.

    After being enabled with OSPF Graceful Restart (GR), a switch can ensure non-stop packet forwarding in the event of a restart caused by an abnormality. In such a case, route flapping is avoided during the short restart of the switch.

Configuring OSPF IP FRR

Configuring BFD for OSPF

Configuring the OSPF GR Helper

Improving stability of an OSPF network

You can improve stability of an OSPF network to reduce route flapping on the OSPF network and enable devices to work in a normal state for a long period of time.

Improving Stability of an OSPF Network

Improving security of an OSPF network

On a network demanding high security, you can configure OSPF authentication and adopt the GTSM mechanism to improve the security of the OSPF network.

Improving Security of an OSPF Network

Updated: 2019-03-21

Document ID: EDOC1000166601

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