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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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RFC 5291 and RFC 5292 define the prefix-based BGP outbound route filtering (ORF) capability to advertise required BGP routes. BGP ORF allows a device to send prefix-based import policies in a Route-refresh message to BGP peers. BGP peers construct export policies based on these import policies to filter routes before sending these routes, which has the following advantages:
  • Prevents the local device from receiving a large number of unnecessary routes.
  • Reduces CPU usage of the local device.
  • Simplifies the configuration of BGP peers.
  • Improves link bandwidth efficiency.

Application Scenarios

BGP ORF applies to the scenario where a device wants BGP peers to send only required routes, and BGP peers do not want to maintain different export policies for different devices.

Figure 9-12 Inter-AS EBGP peers

As shown in Figure 9-12, after negotiating the prefix-based ORF capability with RouterB, RouterA adds the local prefix-based import policies to a Route-refresh message and sends the message to RouterB. RouterB constructs export policies based on the received Route-refresh message and sends required routes to RouterA using a Route-refresh message. RouterA receives only required routes, and RouterB does not need to maintain routing policies. This reduces the configuration workload.

Figure 9-13 Intra-AS route reflector

As shown in Figure 9-13, there is a route reflector (RR) in AS 100. RouterA and RouterB are the clients of the RR. RouterA, RouterB, and the RR negotiate the prefix-based ORF capability. RouterA and RouterB then add the local prefix-based import policies to Route-refresh messages and send the messages to the RR. The RR constructs export policies based on the received import policies and reflects required routes in Route-refresh messages to RouterA and RouterB. RouterA and RouterB receive only required routes, and the RR does not need to maintain routing policies. This reduces the configuration workload.

Updated: 2019-03-21

Document ID: EDOC1000166601

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