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Configuration Guide - IP Routing 01

NE05E and NE08E V300R003C10SPC500

This is NE05E and NE08E V300R003C10SPC500 Configuration Guide - IP Routing
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Huawei uses machine translation combined with human proofreading to translate this document to different languages in order to help you better understand the content of this document. Note: Even the most advanced machine translation cannot match the quality of professional translators. Huawei shall not bear any responsibility for translation accuracy and it is recommended that you refer to the English document (a link for which has been provided).
Configuring BGP4+ Load Balancing

Configuring BGP4+ Load Balancing

Configuring BGP4+ load balancing better utilizes network resources.

Usage Scenario

BGP4+ load balancing can be performed among routes that have the same AS_Path attribute and conform to the first 8 rules in "Route Selection" in BGP Route Processing.

Pre-configuration Tasks

Before configuring BGP4+ load balancing, configure basic BGP4+ functions.

Procedure

  • Configure BGP4+ peer or peer group-based load balancing.

    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.

      NOTE:

      The BGP-IPv6 unicast address family view is used as an example, and you can also configure load balancing in the BGP view, BGP-IPv4 unicast address family view, BGP-IPv6 unicast address family view, BGP-VPN instance IPv4 address family view, or BGP-VPN instance IPv6 address family view.

    4. Run peer { ipv4-address | ipv6–address | group-name } load-balancing [ as-path-ignore | as-path-relax ]

      BGP4+ peer or peer group-based load balancing is configured.

      After the peer load-balancing command is run, BGP peer-based load balancing is implemented only when the following conditions are met:
      • The routes are received from the specified peer or peer group.
      • The optimal route and optimal equal-cost routes exist.
      • The AS_Path attribute is the same as that of the optimal route, or as-path-ignore or as-path-relax is specified in the peer load-balancing command.
        • If as-path-ignore is specified, the device ignores comparing AS_Path attributes when selecting routes for load balancing. In this case, routes can participate in load balancing even if their AS_Path attributes are different.
        • If as-path-relax is specified, the device ignores comparing the AS_Path attributes of the same length when selecting routes for load balancing. In this case, routes cannot participate in load balancing if their AS_Path attributes are of different lengths. For example, the AS_Path attribute of route A is 10, and the AS_Path attribute of route B is 10, 20. Because the two AS_Path attributes are of different lengths, the two routes cannot participate in load balancing.
    5. (Optional) Change load balancing rules.

      • Run the load-balancing as-path-ignore command to prevent the device from comparing AS_Path attributes when selecting routes for load balancing.
      • Run the load-balancing as-path-relax command to configure the device to ignore comparing the AS_Path attributes of the same length when selecting routes for load balancing.
      • Run the load-balancing igp-metric-ignore command to prevent the device from comparing IGP costs when selecting routes for load balancing.
      NOTE:

      The address family views supported by the preceding commands are different. When running any of the commands, ensure that the command is run in the correct address family view.

      Change load balancing rules based on network requirements and exercise caution when running the commands.

    6. Run commit

      The configuration is committed.

  • Configure global BGP4+ load balancing.

    • Set the maximum number of BGP4+ routes for load balancing.
      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 maximum load-balancing [ ebgp | ibgp ] number [ ecmp-nexthop-changed ]

        The maximum number of BGP4+ equal-cost routes for load balancing is set.

        By default, the maximum number of BGP4+ equal-cost routes for load balancing is 1, indicating that load balancing is disabled.

        • ebgp indicates that load balancing is implemented only among EBGP routes.

        • ibgp indicates that load balancing is implemented only among IBGP routes.

        • If neither ebgp nor ibgp is specified, both EBGP and IBGP routes can balance traffic, and the number of EBGP routes for load balancing is the same as the number of IBGP routes for load balancing.

        NOTE:

        By default, traffic cannot be balanced among IBGP and EBGP routes on the public network. If multiple routes with the same destination address exist on the public network, the system selects the optimal route first. If the optimal route is an IBGP route, only IBGP routes carry out load balancing. If the optimal route is an EBGP route, only EBGP routes carry out load balancing.

        The BGP-IPv6 unicast address family view is used as an example, and you can also configure load balancing in the BGP view, BGP-IPv4 unicast address family view, BGP-VPN instance IPv4 address family view, or BGP-VPN instance IPv6 address family view.

      5. (Optional) Change load balancing rules.

        • Run the load-balancing as-path-ignore command to prevent the device from comparing AS_Path attributes when selecting routes for load balancing.
        • Run the load-balancing as-path-relax command to configure the device to ignore comparing the AS_Path attributes of the same length when selecting routes for load balancing.
        • Run the load-balancing igp-metric-ignore command to prevent the device from comparing IGP costs when selecting routes for load balancing.
        NOTE:

        The address family views supported by the preceding commands are different. When running any of the commands, ensure that the command is run in the correct address family view.

        Change load balancing rules based on network requirements and exercise caution when running the commands.

      6. Run commit

        The configuration is committed.

    • Set the maximum number of EBGP and IBGP routes for load balancing.

      This configuration is used in a VPN where a CE is dual-homed to two PEs. When the CE resides in the same AS as only one of the PEs, you can set the maximum number of EBGP and IBGP routes for load balancing so that VPN traffic can be balanced among EBGP and IBGP routes.

      1. Run system-view

        The system view is displayed.

      2. Run bgp as-number

        The BGP view is displayed.

      3. Run ipv6-family vpn-instance vpn-instance-name

        The BGP VPN instance IPv6 address family view is displayed.

      4. Run maximum load-balancing eibgp number [ ecmp-nexthop-changed ]

        The maximum number of EBGP and IBGP routes for load balancing is set.

        By default, the maximum number of EBGP and IBGP routes for load balancing is not set.

        After the maximum load-balancing eibgp number command is run on a device, the device, by default, changes the next hop of each route to itself before advertising the route to a peer, regardless of whether the route is to be used for load balancing ( However, in RR or BGP confederation scenarios, the device does not change the next hop addresses of non-local routes to be advertised to a local address ). However, in RR or BGP4+ confederation scenarios, the device does not change the next hop addresses of non-local routes to be advertised to a local address. As a result, besides the routes for load-balancing, those routes that are not supposed to participate in load balancing deliver traffic to the device, which overburdens the device. To address this problem, you can set ecmp-nexthop-changed so that the device changes the next hop of only routes that are to be used for load balancing to itself before advertising them to peers.

      5. (Optional) Change load balancing rules.

        • Run the load-balancing as-path-ignore command to prevent the device from comparing AS_Path attributes when selecting routes for load balancing.
        • Run the load-balancing as-path-relax command to configure the device to ignore comparing the AS_Path attributes of the same length when selecting routes for load balancing.
        • Run the load-balancing eibgp command to enable load balancing among EBGP and IBGP routes.
        • Run the load-balancing igp-metric-ignore command to prevent the device from comparing IGP costs when selecting routes for load balancing.
        NOTE:

        The address family views supported by the preceding commands are different. When running any of the commands, ensure that the command is run in the correct address family view.

        Change load balancing rules based on network requirements and exercise caution when running the commands.

      6. Run commit

        The configuration is committed.

Checking the Configuration

After the configuration is complete, check whether the configuration has taken effect.

  • Run the display bgp ipv6 routing-table ipv6-address prefix-length command to check routes in the BGP4+ routing table.

# Run the display bgp ipv6 routing-table command. The command output shows that two BGP4+ routes have been selected for load balancing. For example:

<HUAWEI> display bgp ipv6 routing-table 8::1 64
 BGP local router ID : 1.1.1.1
 Local AS number : 100
 Paths : 2 available, 1 best, 2 select
 BGP routing table entry information of 8::/64:
 From: 2001:db8:20:1::2 (2.2.2.2)
 Route Duration: 0d00h02m00s
 Direct Out-interface: GigabitEthernet0/3/0
 Original nexthop: 2001:db8:20:1::2
 AS-path 300 200, origin igp, pref-val 0, valid, external, best, select, pre 255
 Advertised to such 2 peers:
    2001:db8:20:1::2
    2001:db8:20:2::2

 BGP routing table entry information of 8::/64:
 From: 2001:db8:20:2::2 (3.3.3.3)
 Route Duration: 0d00h02m00s
 Direct Out-interface: GigabitEthernet0/3/1
 Original nexthop: 2001:db8:20:2::2
 AS-path 300 200, origin igp, pref-val 0, valid, external, select, pre 255, not
preferred for router ID
 Not advertised to any peers yet
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Updated: 2019-01-14

Document ID: EDOC1100058916

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