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NE40E V800R010C10SPC500 Configuration Guide - IP Routing 01

This is NE40E V800R010C10SPC500 Configuration Guide - IP Routing
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Configuring IPv4 IS-IS Route Summarization

Configuring IPv4 IS-IS Route Summarization

To speed up IPv4 route lookup and simplify route management on a large-scale IS-IS network, configure IS-IS route summarization to reduce the number of IS-IS routes in a routing table.

Usage Scenario

The IS-IS routing table of a device on a medium or large IS-IS network contains a large number of routing entries. Storing the routing table consumes a large number of memory resources, and transmitting and processing routing information consume lots of network resources. IS-IS route summarization can solve this problem.

Route summarization is the process of summarizing routes that share the same next hop but are destined for different subnets of a network segment into one route. The system then advertises the summarized route to other network segments. Route summarization on a large-scale IS-IS network reduces the number of routes in a routing table and minimizes system resource consumption. In addition, if a specific link frequently alternates between Up and Down, the link status changes will not be advertised to devices that are located beyond the summarized route network segment, which prevents route flapping and improves network stability.

Pre-configuration Tasks

Before configuring IS-IS route summarization, complete the following tasks:

  • Configure IP addresses for interfaces to ensure that neighboring devices are reachable at the network layer.


  1. Run system-view

    The system view is displayed.

  2. Run isis [ process-id ]

    The IS-IS view is displayed.

  3. Run summary ip-address mask [ avoid-feedback | generate_null0_route | tag tag-value | [ level-1 | level-1-2 | level-2 ] ] *

    The specified IS-IS routes are summarized into one IS-IS route.


    After route summarization is configured on an IS, the local IPv4 routing table still contains all specific routes before the summarization.

    The IPv4 routing tables on other ISs that receive the LSP from the local IS contain only the summarized route, and the summarized route is deleted only after all its specific routes are deleted.

  4. Run commit

    The configuration is committed.

Checking the Configurations

After configuring route summarization, perform the following steps to check whether the route summarization function has taken effect.
  • Run the display isis route command to check summarized routes in the IS-IS routing table.

  • Run the display ip routing-table [ verbose ] command to check summarized routes in the IP routing table.

Run the display isis route command to check summarized routes in IS-IS process 1.

<HUAWEI> display isis route
                         Route information for ISIS(1)
                        ISIS(1) Level-2 Forwarding Table
 IPV4 Destination     IntCost    ExtCost ExitInterface   NextHop         Flags
----------------------------------------------------------------------------         20         NULL    GE2/0/0       A/-/L/-         10         NULL    GE2/0/0         Direct          D/-/L/-

     Flags: D-Direct, A-Added to URT, L-Advertised in LSPs, S-IGP Shortcut,
                               U-Up/Down Bit Set
Updated: 2019-01-03

Document ID: EDOC1100055018

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