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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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BGP-LS

BGP-LS

BGP-link state (LS) enables BGP to report topology information collected by IGPs to the controller.

BGP-LS is a new method of collecting topology information.

Without BGP-LS, the Switch uses an IGP (OSPF or IS-IS) to collect topology information of each AS, and the IGP reports the information to the controller. This topology information collection method has the following disadvantages:
  • The controller must have high computing capabilities and support the IGP and its algorithm.
  • The controller cannot gain the complete inter-AS topology information and therefore is unable to calculate optimal E2E paths.
  • Different IGPs report topology information separately to the controller, which complicates the controller's analysis and processing.
With powerful routing capabilities of BGP, BGP-LS has the following advantages:
  • Reduces computing capability requirements and spares the necessity of IGPs on the controller.
  • Facilitates route selection and calculation on the controller by using BGP to summarize process or AS topology information and report the complete information to the controller.
  • Requires only one routing protocol (BGP) to report topology information to the controller.

Related Concepts

BGP-LS provides a simple and efficient method of collecting topology information.

BGP-LS routes carry topology information and are classified into three types of routes that carry node, link, and route prefix information, respectively. Theses routes collaborate in carrying topology information.

Format of node routes

For example, a node route is in the format of [NODE][ISIS-LEVEL-1][IDENTIFIER0][LOCAL[as100][bgp-ls-identifier11.1.1.2][ospf-area-id0.0.0.0][igp-router-id0000.0000.0001.00]].

Node routes carry node information.

Table 9-5 describes the fields in node routes.

Table 9-5 Description of the fields in node routes

Item

Description

NODE

Field indicating that the BGP-LS route is a node route.

ISIS-LEVEL-1

Protocol that collects topology information. The protocol is IS-IS in this example.

IDENTIFIER0

Identifier of the protocol that collects topology information.

LOCAL

Field indicating information of a local node.

as

BGP-LS domain AS number.

bgp-ls-identifier

BGP-LS domain ID.

ospf-area-id

OSPF area ID.

igp-router-id

IGP router ID, generated by the IGP that collects topology information. The router ID is obtained from the NET of an IS-IS process in this example.

Format of link routes

For example, a link route is in the format of [LINK][ISIS-LEVEL-1][IDENTIFIER0][LOCAL[as255.255][bgp-ls-identifier192.168.102.4][ospf-area-id0.0.0.0][igp-router-id0000.0000.0002.01]][REMOTE[as255.255][bgp-ls-identifier192.168.102.4][ospf-area-id0.0.0.0][igp-router-id0000.0000.0002.00]][LINK[if-address0.0.0.0][peer-address0.0.0.0][if-address::][peer-address::][mt-id0]].

Link routes carry information about links between devices.

Table 9-6 describes the fields in link routes.

Table 9-6 Description of the fields in link routes

Item

Description

LINK

Field indicating that the BGP-LS route is a link route.

ISIS-LEVEL-1

Protocol that collects topology information. The protocol is IS-IS in this example.

IDENTIFIER0

Identifier of the protocol that collects topology information.

LOCAL

Field indicating information of a local node.

as

BGP-LS domain AS number.

bgp-ls-identifier

BGP-LS domain ID.

ospf-area-id

OSPF area ID.

igp-router-id

IGP router ID, generated by the IGP that collects topology information. The router ID is obtained from the NET of an IS-IS process in this example.

REMOTE

Field indicating information of a remote node.

if-address

IP address of the local interface.

peer-address

IP address of the remote interface.

mt-id

ID of the topology.

Format of prefix routes

For example, a prefix route is in the format of [IPV4-PREFIX][ISIS-LEVEL-1][IDENTIFIER0][LOCAL[as100][bgp-ls-identifier192.168.102.3][ospf-area-id0.0.0.0][igp-router-id0000.0000.0001.00]][PREFIX[mt-id0][ospf-route-type0][prefix192.168.102.0/24]].

Prefix routes carry information about reachable network segments.

Table 9-7 describes the fields in link routes.

Table 9-7 Description of the fields in prefix routes

Item

Description

IPV4-PREFIX

Field indicating an IPv4 or IPv6 prefix route. The Switch cannot generate IPv6 prefix routes, but it can process the IPv6 prefix routes received from non-Huawei devices.

ISIS-LEVEL-1

Protocol that collects topology information. The protocol is IS-IS in this example.

IDENTIFIER0

Identifier of the protocol that collects topology information.

LOCAL

Field indicating information of a local node.

as

BGP-LS domain AS number.

bgp-ls-identifier

BGP-LS domain ID.

ospf-area-id

OSPF area ID.

igp-router-id

IGP router ID, generated by the IGP that collects topology information. The router ID is obtained from the NET of an IS-IS process in this example.

PREFIX

Field indicating an IGP route.

mt-id

ID of the topology.

ospf-route-type

OSPF route type:
  • 1: Intra-Area
  • 2: Inter-Area
  • 3: External 1
  • 4: External 2
  • 5: NSSA 1
  • 6: NSSA 2
prefix

Prefix of an IGP route.

Application Scenarios

Networking in which topology information is collected within an IGP area

In Figure 9-17, SwitchA, SwitchB, SwitchC, and SwitchD use IS-IS to communicate with each other at the network layer. They are all Level-2 devices in the same area (area 10). Only one of the four devices needs to have BGP-LS deployed and establish a BGP-LS peer relationship with the controller so that BGP-LS can collect and report topology information to the controller. To improve reliability, deploying BGP-LS on two or more devices and establishing a BGP-LS peer relationship between each BGP-LS device and the controller are recommended. The BGP-LS devices collect the same topology information, and they back up each other in case one of them fails.

Figure 9-17 Networking in which topology information is collected within an IGP area

Networking in which topology information is collected between IGP areas

In Figure 9-18, SwitchA, SwitchB, SwitchC, and SwitchD use IS-IS to communicate with each other at the network layer. SwitchA, SwitchB, and SwitchC reside in area 10, whereas SwitchD resides in area 20. SwitchA and SwitchB are Level-1 devices, SwitchC is a Level-1-2 device, and SwitchD is a Level-2 device. Only one of the four devices needs to have BGP-LS deployed and establish a BGP-LS peer relationship with the controller so that BGP-LS can collect and report topology information to the controller. To improve reliability, deploying BGP-LS on two or more devices and establishing a BGP-LS peer relationship between each BGP-LS device and the controller are recommended. The BGP-LS devices collect the same topology information, and they back up each other in case one of them fails.

Figure 9-18 Networking in which topology information is collected between IGP areas

Networking in which topology information is collected between BGP ASs

In Figure 9-19, SwitchA and SwitchB belong to the same AS, and an IS-IS neighbor relationship is established between them. BGP is disabled on SwitchA. An EBGP peer relationship is established between SwitchB and SwitchC. If BGP-LS is disabled, BGP cannot exchange topology information between AS 100 and AS 200. As a result, the topology information collected in AS 100 is different from that collected in AS 200. To address this problem, enable BGP-LS on at least one device (two or more is recommended for higher reliability) in each AS and establish a BGP-LS peer relationship between each of the devices and the controller.

Figure 9-19 Networking 1 in which topology information is collected between BGP ASs

If two controllers are deployed and are connected to different ASs, for example in Figure 9-20, a BGP-LS peer relationship must be established between the two controllers or between SwitchB and SwitchC so that both controllers can obtain topology information on the whole network.

Figure 9-20 Networking 2 in which topology information is collected between BGP ASs
NOTE:

To reduce the number of connections to the controller, deploy one or more BGP-LS RRs and establish BGP-LS peer relationships between each RR and the devices that require BGP-LS peer relationships with the controller.

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Updated: 2019-03-21

Document ID: EDOC1000166601

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