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NE40E V800R010C10SPC500 Configuration Guide - IP Routing 01

This is NE40E V800R010C10SPC500 Configuration Guide - IP Routing
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Configuring BGP4+ RRs

Configuring BGP4+ RRs

BGP4+ RRs avoid fully meshed connections between multiple IBGP peers, which reduces network costs.

Usage Scenario

Fully meshed connections need to be established between IBGP peers to ensure the connectivity between IBGP peers. If there are n routers in an AS, n x (n-1)/2 IBGP connections need to be established. When there are a lot of IBGP peers, network resources and CPU resources are greatly consumed. Route reflection can solve the problem.

Using RRs reduces the total number of IBGP connections. On a large network, however, multiple RRs need to be configured to reduce the number of clients of each RR. Therefore, there are still a large number of IBGP connections on the network because fully meshed connections need to be established between the RRs. In this situation, configure hierarchical RR to further reduce the number of IBGP connections.

Figure 11-3 shows a typical hierarchical RR networking. Device A, Device B, Device C, and Device D function as level-2 RRs; Device E, Device F, Device G, and Device H function as level-1 RRs and the clients of level-2 RRs. Level-2 RRs are not the clients of any RR and must be fully meshed. Level-1 RRs function as the clients of level-2 RRs and do not need to be fully meshed.

Figure 11-3 Networking with hierarchical RRs

Pre-configuration Tasks

Before configuring BGP4+ RRs, configure basic BGP4+ functions.

Configuration Procedures

Figure 11-4 Flowchart for configuring BGP4+ RRs

Configuring an RR and Specifying Its Clients

RRs reflect routes between clients, and therefore IBGP connections do not need to be established between the clients.

Context

In an AS, one router functions as an RR, and the other routers function as its clients. The clients establish IBGP connections with the RR. The RR and its clients form a cluster. The RR transmits or reflects routes among clients, but the clients do not need to establish any IBGP connections between each other.

An RR is easy to configure because it needs to be configured only on the router that functions as a reflector and clients do not need to know that they are clients.

Procedure

  1. Run system-view

    The system view is displayed.

  2. Run bgp as-number

    The BGP view is displayed.

  3. Run ipv6-family unicast

    The IPv6 unicast address family view is displayed.

  4. Run peer { ipv6-address | ipv4-address | group-name } reflect-client

    An RR and its clients are configured.

    The router where the peer reflect-client command is run functions as the RR, and specified peers or peer groups function as the clients.

    NOTE:

    reflect-client configured in an address family is valid in this family address and cannot be inherited by other address families.

  5. Run commit

    The configuration is committed.

(Optional) Disabling Route Reflection Between Clients Through the RR

If the clients of an RR are fully meshed, you can disable route reflection among them through the RR to reduce bandwidth consumption.

Context

On some networks, if the clients of an RR have established IBGP peer relationships with each other, they can directly exchange routing information. Route reflection between the clients through the RR is unnecessary. In this case, disable route reflection among them through the RR.

Procedure

  1. Run system-view

    The system view is displayed.

  2. Run bgp as-number

    The BGP view is displayed.

  3. Run ipv6-family unicast

    The IPv6 unicast address family view is displayed.

  4. Run undo reflect between-clients

    Route reflection among clients through the RR is disabled.

    If the clients of an RR have been fully meshed, you can run the undo reflect between-clients command to disable route reflection among the clients through the RR. The undo reflect between-clients command is run only on RRs.

  5. Run commit

    The configuration is committed.

(Optional) Configuring a Cluster ID for RRs

If a cluster has multiple RRs, you can configure the same cluster ID for these RRs to prevent routing loops.

Context

Under some circumstances, more than one RR needs to be configured in a cluster to improve network reliability and prevent single points of failure. The same cluster ID needs to be configured for all the RRs in the cluster to reduce the number of routes received by each RR. This reduces network cost.

NOTE:

To allow clients to receive routes reflected by RRs, ensure that the cluster ID of the RRs is different from the router ID of any client. If the cluster ID of the RRs is the same as the router ID of a client, the client will discard received routes.

Procedure

  1. Run system-view

    The system view is displayed.

  2. Run bgp as-number

    The BGP view is displayed.

  3. Run ipv6-family unicast

    The IPv6 unicast address family view is displayed.

  4. Run reflector cluster-id cluster-id

    A cluster ID is configured for RRs.

    If a cluster has multiple RRs, you can use this command to set the same cluster ID for these RRs.

    The reflector cluster-id command is run only on RRs.

  5. Run commit

    The configuration is committed.

(Optional) Enabling the RR to Modify the Route Attributes Based on the Export Policy

You can enable the RR to modify the route attributes based on the export policy to change route selection results of the BGP4+.

Context

The route attributes on the RR cannot be modified using the export policy because it may cause routing loops. By default, the RR is disabled from modifying the route attributes based on the export policy. But if you need to re-plan the network traffic, you can enable the RR to modify the route attributes based on the export policy.

Procedure

  1. Run system-view

    The system view is displayed.

  2. Run bgp as-number

    The BGP view is displayed.

  3. Run ipv6-family unicast

    The IPv6 unicast address family view is displayed.

  4. Run reflect change-path-attribute

    You can enable the RR to modify the route attributes of the BGP4+ routes based on the export policy.

    After you enable the reflect change-path-attribute command on an RR, the configurations of the RR attributes modified using the export policy takes effect immediately. Perform the following operations:
    • Run the apply as-path command to modify the AS-Path attributes of BGP4+ routes.
    • Run the apply comm-filter delete command to delete all community attributes from a BGP4+ route.
    • Run the apply community command to modify the AS-Path attributes of BGP4+ routes.
    • Run the apply cost command to modify the MED of BGP4+ routes.
    • Run the apply ipv6 next-hop command to modify the next hop of BGP4+ routes.
    • Run the apply local-preference command to modify the local preference of BGP4+ routes.
    • Run the apply origin command to modify the Origin attributes of BGP4+ routes.
    • Run the apply extcommunity command to modify the VPN-Target extended community attributes of BGP4+ routes.
    NOTE:

    After the reflect change-path-attribute command is run on the RR, the peer route-policy export command takes precedence over the peer next-hop-invariable and peer next-hop-local commands.

  5. Run commit

    The configuration is committed.

Verifying the Configuration of BGP4+ RRs

After configuring BGP4+ RRs, check information about BGP4+ routes and peer groups.

Prerequisites

BGP4+ RRs have been configured.

Procedure

  • Run the display bgp ipv6 peer [ verbose ] command to check detailed information about peers and check whether an RR and its clients are successfully configured.
  • Run the display bgp ipv6 routing-table command to check the routes to an RR.
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Updated: 2019-01-03

Document ID: EDOC1100055018

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