Contents

Introduction· 1

Prerequisites· 1

Example: Configuring IS-IS route summarization· 1

Network configuration· 1

Analysis· 2

Procedures· 2

Configuring IP addresses for interfaces· 2

Configuring basic IS-IS· 3

Configuring IS-IS route summarization· 4

Verifying the configuration· 4

Configuration files· 5

Device A· 5

Device B· 5

GW 1· 6

 

Introduction

This document provides IS-IS route summarization configuration examples.

Prerequisites

The configuration examples in this document were created and verified in a lab environment, and all the devices were started with the factory default configuration. When you are working on a live network, make sure you understand the potential impact of every command on your network.

This document assumes that you have basic knowledge of IS-IS route summarization.

Example: Configuring IS-IS route summarization

Network configuration

As shown in Figure 1, the five departments of a company use IS-IS to connect to the backbone network. The three departments are assigned the networks 192.168.1.0/24, 192.168.2.0/24, 192.168.3.0/24. Configure IS-IS route summarization to reduce routing entries and save system resources for Device B.

Figure 1 Network diagram

‌

Device	Interface	IP Address	Device	Interface	IP Address
Device A	XGE3/1/4	172.16.1.1/24	Device B	XGE3/1/1	172.16.1.2/24
	XGE3/1/1	10.1.1.1/24	GW 1	XGE3/1/1	10.1.1.2/24
	XGE3/1/2	10.1.2.1/24	GW 2	XGE3/1/2	10.1.2.2/24
	XGE3/1/3	10.1.3.1/24	GW3	XGE3/1/3	10.1.3.2/24

‌

Analysis

Configure route summarization on Device A because route summarization applies only to locally generated LSPs.

To avoid blackhole routes, set the summary route to 192.168.0.0/22.

Procedures

Configuring IP addresses for interfaces

# Configure an IP address for interface Ten-GigabitEthernet 3/1/4 on Device A.

<DeviceA> system-view

[DeviceA] interface ten-gigabitethernet 3/1/4

[DeviceA-Ten-GigabitEthernet3/1/4] ip address 172.16.1.1 24

[DeviceA-Ten-GigabitEthernet3/1/4] quit

# Configure IP addresses for other interfaces as shown in Figure 1 in the same way VLAN-interface 10 is configured. (Details not shown.)

Configuring basic IS-IS

Configuring Device A

# Enable IS-IS on Device A and configure Device A as a Level-1-2 router.

[DeviceA] isis 1

[DeviceA-isis-1] network-entity 10.0000.0000.0001.00

[DeviceA-isis-1] is-level level-1-2

[DeviceA-isis-1] quit

# Enable IS-IS on interface Ten-GigabitEthernet 3/1/4.

[DeviceA] interface ten-gigabitethernet 3/1/4

[DeviceA–Ten-GigabitEthernet3/1/4] isis enable 1

[DeviceA–Ten-GigabitEthernet3/1/4] quit

# Configure other interfaces in the same way VLAN-interface 10 is configured. (Details not shown.)

Configuring Device B

# Enable IS-IS on Device B and configure Device B as a Level-2 router.

[DeviceB] isis 1

[DeviceB-isis-1] network-entity 10.0000.0000.0002.00

[DeviceB-isis-1] is-level level-2

[DeviceB-isis-1] quit

# Enable IS-IS on interface Ten-GigabitEthernet 3/1/1.

[DeviceB] interface ten-gigabitethernet 3/1/1

[DeviceB–Ten-GigabitEthernet3/1/1] isis enable 1

[DeviceB–Ten-GigabitEthernet3/1/1] quit

Configuring the gateways

# Enable IS-IS on GW 1 and configure GW 1 as a Level-1 router.

[GW1] isis 1

[GW1-isis-1] network-entity 10.0001.0001.0001.00

[GW1-isis-1] is-level level-1

[GW1-isis-1] quit

# Enable IS-IS on interface Ten-GigabitEthernet 3/1/1.

[GW1] interface ten-gigabitethernet 3/1/1

[GW1–Ten-GigabitEthernet3/1/1] isis enable 1

[GW1–Ten-GigabitEthernet3/1/1] quit

# Configure other gateways in the same way GW 1 is configured. (Details not shown.)

Displaying IS-IS routing information on Device B

# Display IS-IS routing information on Device B to view the network address of each department.

[DeviceB] display isis route

 

Route information for IS-IS(1)

 

                         -----------------------------

                         Level-2 IPv4 Forwarding Table

                         -----------------------------

 

 IPv4 Destination     IntCost    ExtCost ExitInterface   NextHop         Flags

-------------------------------------------------------------------------------

 192.168.1.0/24       30         NULL    XGE3/1/1        172.16.1.1      R/-/-

 10.1.1.0/24          20         NULL    XGE3/1/1         172.16.1.1      R/-/-

 192.168.2.0/24       30         NULL    XGE3/1/1        172.16.1.1      R/-/-

 10.1.2.0/24          20         NULL    XGE3/1/1        172.16.1.1      R/-/-

 192.168.3.0/24       30         NULL    XGE3/1/1        172.16.1.1      R/-/-

 10.1.3.0/24          20         NULL    XGE3/1/1        172.16.1.1      R/-/-

 172.16.1.0/24        10         NULL    XGE3/1/1        Direct          D/L/-

 

      Flags: D-Direct, R-Added to Rib, L-Advertised in LSPs, U-Up/Down Bit Set

Configuring IS-IS route summarization

# Configure IS-IS route summarization on Device A.

[DeviceA] isis 1

[DeviceA-isis-1]address-family ipv4

[DeviceA-isis-1-ipv4] summary 192.168.0.0 22

Verifying the configuration

# Display IS-IS routing information on Device B.

[DeviceB] display isis route

 

                         Route information for IS-IS(1)

                         ------------------------------

 

                         Level-2 IPv4 Forwarding Table

                         -----------------------------

 

 IPv4 Destination     IntCost    ExtCost ExitInterface   NextHop         Flags

-------------------------------------------------------------------------------

 10.1.1.0/24          20         NULL    XGE3/1/1        172.16.1.1      R/-/-

 10.1.2.0/24          20         NULL    XGE3/1/1        172.16.1.1      R/-/-

 10.1.3.0/24          20         NULL    XGE3/1/1        172.16.1.1      R/-/-

 172.16.1.0/24        10         NULL    XGE3/1/1        Direct          D/L/-

 192.168.0.0/22       30         NULL    XGE3/1/1        172.16.1.1      R/-/-

 

      Flags: D-Direct, R-Added to Rib, L-Advertised in LSPs, U-Up/Down bit set

The output shows that the networks have been summarized into a single network 192.168.0.0/22.

Configuration files

Device A

#

isis 1

 network-entity 10.0000.0000.0001.00

 #

 address-family ipv4 unicast

  summary 192.168.0.0 255.255.252.0

#

interface ten-gigabitethernet 3/1/4

 port link-mode route

 ip address 172.16.1.1 255.255.255.0

 isis enable 1

#

interface ten-gigabitethernet 3/1/1

 port link-mode route

 ip address 10.1.1.1 255.255.255.0

 isis enable 1

#

interface ten-gigabitethernet 3/1/2

 port link-mode route

 ip address 10.1.2.1 255.255.255.0

 isis enable 1

#

interface ten-gigabitethernet 3/1/3

 port link-mode route

 ip address 10.1.3.1 255.255.255.0

 isis enable 1

#

Device B

#

isis 1

 is-level level-2

 network-entity 10.0000.0000.0002.00

#

interface ten-gigabitethernet 3/1/1

 port link-mode route

 ip address 172.16.1.2 255.255.255.0

 isis enable 1

#

GW 1

#

isis 1

 is-level level-1

 network-entity 10.0001.0001.0001.00

#

interface ten-gigabitethernet 3/1/1

 port link-mode route

 ip address 10.1.1.2 255.255.255.0

 isis enable 1

#

interface ten-gigabitethernet 3/1/2

 port link-mode route

 ip address 192.168.1.1 255.255.255.0

 isis enable 1

#

The configuration files for other gateways are similar to the configuration file for GW 1. (Details not shown.)