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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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Configuring IS-IS Neighbor Relationship Flapping Suppression

Configuring IS-IS Neighbor Relationship Flapping Suppression

Usage Scenario

If an interface transmitting IS-IS services alternates between Up and Down, IS-IS neighbor relationship flapping occurs on the interface. During the flapping, IS-IS reestablishes the neighbor relationship and recalculates routes. In this process, a large number of packets are exchanged, adversely affecting neighbor relationship stability, IS-IS services, and other IS-IS-dependent services, such as LDP and BGP. IS-IS neighbor relationship flapping suppression can address this problem by delaying IS-IS neighbor relationship reestablishment or preventing service traffic from passing through flapping links.

Pre-configuration Tasks

Before configuring IS-IS neighbor relationship flapping suppression, complete the following tasks:


  1. Run system-view

    The system view is displayed.

    By default, IS-IS neighbor relationship flapping suppression is enabled globally. To disable this function globally, run the suppress-flapping peer disable command in the IS-IS view.

  2. Run interface interface-type interface-number

    The interface view is displayed.

    By default, IS-IS neighbor relationship flapping suppression is enabled on all interfaces in the same IS-IS process. To disable the function from one of the interfaces, run the isis suppress-flapping peer disable command.

  3. On an Ethernet interface, run undo portswitch

    The interface is switched to Layer 3 mode.

    By default, an Ethernet interface works in Layer 2 mode.

    The mode switching function takes effect when the interface only has attribute configurations (for example, shutdown and description configurations). Alternatively, if configuration information supported by both Layer 2 and Layer 3 interfaces exists (for example, mode lacp and lacp system-id configurations), no configuration that is not supported after the working mode of the interface is switched can exist. If unsupported configurations exist on the interface, delete the configurations first and then run the undo portswitch command.


    If many Ethernet interfaces need to be switched to Layer 3 mode, run the undo portswitch batch interface-type { interface-number1 [ to interface-number2 ] } &<1-10> command in the system view to switch these interfaces to Layer 3 mode in batches.

  4. Run isis suppress-flapping peer hold-down interval

    The Hold-down mode is configured, and its duration is set.

    Flapping suppression works in either Hold-down or Hold-max-cost mode.

    • Hold-down mode: In the case of frequent flooding and topology changes during neighbor relationship establishment, interfaces prevent neighbor relationship reestablishment during Hold-down suppression, which minimizes synchronization attempts and packet exchanges.
    • Hold-max-cost mode: If the traffic forwarding path changes frequently, interfaces use the maximum value (16777214 for the wide mode and 63 for the narrow mode) as the cost of the flapping link during Hold-max-cost suppression, which prevents traffic from passing through the flapping link.

    Flapping suppression can also work first in Hold-down mode and then in Hold-max-cost mode.

    By default, the Hold-down mode is disabled, and the Hold-max-cost mode is enabled.

    To disable this mode, run the isis suppress-flapping peer hold-max-cost disable command.

  5. Run isis suppress-flapping peer { detecting-interval detecting-interval | threshold threshold | resume-interval resume-interval } *

    Detection parameters are configured for IS-IS neighbor relationship flapping suppression.

    Each IS-IS interface on which IS-IS neighbor relationship flapping suppression is enabled starts a flapping counter. If the interval between two successive neighbor status changes from Full to a non-Full state is shorter than detecting-interval, a valid flapping_event is recorded, and the flapping_count increases by 1. When the flapping_count reaches or exceeds threshold, flapping suppression takes effect. If the interval between two successive neighbor status changes from Full to a non-Full state is longer than resume-interval, the flapping_count is reset.


    The value of resume-interval must be greater than that of detecting-interval.

    By default, the detection interval of IS-IS neighbor relationship flapping suppression is 60s, the suppression threshold is 10, and the interval for exiting from suppression is 120s. Using the default detection parameters is recommended.

  6. Run commit

    The configuration is committed.

Verifying the Configuration

Run the display isis interface interface-type interface-number [ verbose ] command to check the status of IS-IS neighbor relationship flapping suppression.

Updated: 2019-03-21

Document ID: EDOC1000166601

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