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ME60 V800R010C10SPC500 Configuration Guide - IP Routing 01

This is ME60 V800R010C10SPC500 Configuration Guide - IP Routing
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Configuring BGP4+ Iteration Suppression in Case of Next Hop Flapping

Configuring BGP4+ Iteration Suppression in Case of Next Hop Flapping

BGP4+ iteration suppression in case of next hop flapping prevents the system from frequently processing changes of a large number of routes that are iterated to a flapping next hop, which reduces system resource consumption and CPU usage.

Usage Scenario

If a large number of routes are iterated to the same next hop that flaps frequently, the system will be busy processing changes of these routes, which consumes excessive system resources and leads to high CPU usage. To address this problem, configure BGP4+ iteration suppression in case of next hop flapping.

By default, BGP4+ iteration suppression in case of next hop flapping is enabled. After this function is enabled, BGP4+ calculates the penalty value that starts from 0 by comparing the flapping interval with configured intervals if next hop flapping occurs. When the penalty value exceeds 10, BGP4+ suppresses route iteration to the corresponding next hop. For example, if the intervals for increasing, retaining, and clearing the penalty value are T1, T2, and T3, respectively, BGP4+ calculates the penalty value as follows:
  • Increases the penalty value by 1 if the flapping interval is less than T1.
  • Retains the penalty value if the flapping interval is greater than or equal to T1, but less than T2.
  • Reduces the penalty value by 1 if the flapping interval is greater than or equal to T2, but less than T3.
  • Clears the penalty value if the flapping interval is greater than or equal to T3.

Pre-configuration tasks

Before configuring BGP iteration suppression in case of next hop flapping, configure basic BGP4+ functions.

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 nexthop recursive-lookup restrain disable

    BGP iteration suppression in case of next hop flapping is enabled.

    If you do not care about whether the system is busy processing route selection and advertisement and the possible high CPU usage, run the nexthop recursive-lookup restrain disable command to disable BGP iteration suppression in case of next hop flapping.

  5. Run quit

    Return to the BGP view.

  6. Run nexthop recursive-lookup restrain suppress-interval add-count-time hold-interval hold-count-time clear-interval clear-count-time

    The intervals are configured for increasing, retaining, and clearing the penalty value for BGP iteration suppression in case of next hop flapping.

  7. Run commit

    The configuration is committed.

Checking the Configurations

After configuring BGP4+ iteration suppression in case of next hop flapping, check the configurations.

  • Run the display bgp ipv6 routing-table command to check BGP4+ public network route information.
  • Run the display bgp vpnv6 routing-table command to check BGP VPNv6 and BGP VPN route information.

# Run the display bgp ipv6 routing-table command to view BGP4+ public network route information. The command output shows that route iteration to a specified next hop is suppressed because the next hop flaps. If only a small number of routes are iterated to the next hop, the suppression is very short; therefore, the Relay is delayed as nexthop flapped frequently field may not be displayed in this case.

<HUAWEI> display bgp ipv6 routing-table 111::111 128
 BGP local router ID : 3.3.3.3
 Local AS number : 100
 Paths:   2 available, 1 best, 1 select , 0 best-external, 0 add-path
 BGP routing table entry information of 111::111/128:
 From: 30::2 (4.4.4.4)
 Route Duration: 00h25m46s
 Relay IP Nexthop: 30::2
 Relay IP Out-Interface: GigabitEthernet1/0/2
 Original nexthop: 50::2
 AS-path 300, origin incomplete, MED 0, localpref 100, pref-val 0, valid, internal, best, select, pre 255
 Not advertised to any peers yet
 BGP routing table entry information of 111::111/128:
 From: 40::2 (5.5.5.5)
 Route Duration: 00h25m44s
 Relay IP Nexthop: 40::2
 Relay IP Out-Interface: GigabitEthernet1/0/3
 Relay is delayed as nexthop flapped frequently
 Original nexthop: 60::2
 Primary Routing Table: vrf1
 AS-path 300, origin incomplete, MED 0, localpref 100, pref-val 0, valid, internal, active, pre 255 , not preferred for router ID
 Not advertised to any peers yet

# Run the display bgp vpnv6 routing-table command to view BGP VPNv6 route information. The command output shows that route iteration to a specified next hop is suppressed because the next hop flaps. If only a small number of routes are iterated to the next hop, the suppression is very short; therefore, the Relay is delayed as nexthop flapped frequently field may not be displayed in this case.

<HUAWEI> display bgp vpnv6 routing-table 2001:db8:1::
 BGP local router ID : 1.1.1.2
 Local AS number : 200
 
 Total routes of Route Distinguisher(6:7): 2
 BGP routing table entry information of 2001:db8:1::/48:
 Label information (Received/Applied): NULL/64
 From: 2001::1 (1.1.1.1)  
 Route Duration: 0d00h01m03s
 Direct Out-interface: GigabitEthernet3/0/3
 Relay is delayed as nexthop flapped frequently
 Original nexthop: 2001::1
 Ext-Community: RT <1 : 1>
 AS-path 100, origin incomplete, MED 0, pref-val 0, valid, external, best, select, pre 255
 Advertised to such 1 peers:
    1.1.1.1
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Updated: 2019-01-04

Document ID: EDOC1100059437

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