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NE40E V800R010C10SPC500 Configuration Guide - IP Routing 01

This is NE40E V800R010C10SPC500 Configuration Guide - IP Routing
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Configuring BGP Next Hop Iteration Based on a Route-Policy

Configuring BGP Next Hop Iteration Based on a Route-Policy

Configuring BGP next hop iteration based on a route-policy prevents traffic loss if routes changes.

Usage Scenario

When BGP routes change, BGP needs to perform route iteration on the BGP routes with indirect next hops. If no route-policies are configured to filter the routes on which a BGP route with an indirect next hop depends for iteration, the BGP route may be iterated to an incorrect route, which may cause traffic loss. To address this problem, configure BGP next hop iteration based on a route-policy. If no routes match the route-policy, the BGP route with an indirect next hop is considered unreachable. In this situation, incorrect route iteration and traffic loss are prevented.

Pre-configuration Tasks

Before configuring BGP next hop iteration based on a route-policy, complete the following tasks:

Before configuring a route-policy, ensure that the routes on which BGP routes with indirect next hops depend for iteration will not be filtered out by the route-policy. Otherwise, route iteration fails, and traffic cannot be forwarded.

Procedure

  1. Run system-view

    The system view is displayed.

  2. Run bgp as-number

    The BGP view is displayed.

  3. Run nexthop recursive-lookup { route-policy route-policy-name | route-filter route-filter-name }

    BGP next hop iteration based on a route-policy or route-filter is configured.

    NOTE:

    The command does not apply to the routes received from directly connected EBGP peers or LinkLocal peers.

  4. Run commit

    The configuration is committed.

Checking the Configurations

Run the following commands to check the previous configuration.

  • Run the display bgp routing-table network [ mask | mask-length ] command to check detailed information about a specified route in the BGP routing table.

# Run the display bgp routing-table network [ mask | mask-length ] command to view detailed information about a specified route in the BGP routing table. The command output shows that the next hop of the route that is filtered out by the route-policy has been set to 0.0.0.0 and that the outbound interface has been set to null.

<HUAWEI> display bgp routing-table 4.4.4.4 32
 
 BGP local router ID : 1.1.1.1
 Local AS number : 100
 Paths:   2 available, 1 best, 1 select
 BGP routing table entry information of 4.4.4.4/32:
 From: 3.3.3.3 (3.3.3.3)  
 Route Duration: 0d00h11m41s
 Relay IP Nexthop: 200.1.2.2
 Relay IP Out-interface: GigabitEthernet1/0/2
 Original nexthop: 3.3.3.3
 Qos information : 0x0            
 AS-path 200, origin igp, MED 1, pref-val 0, valid, external, best, select, pre 255
 Advertised to such 2 peers:
    3.3.3.3
    2.2.2.2

 BGP routing table entry information of 4.4.4.4/32:
 From: 2.2.2.2 (2.2.2.2)  
 Route Duration: 0d00h15m48s
 Relay IP Nexthop: 0.0.0.0
 Relay IP Out-interface: 
 Original nexthop: 2.2.2.2
 Qos information : 0x0            
 AS-path 200, origin igp, MED 1, pref-val 0, external, pre 255
 Not advertised to any peers yet
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Updated: 2019-01-03

Document ID: EDOC1100055018

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