Example for Configuring IS-IS Route Summarization
Networking Requirements
As shown in Figure 7-35, three routers run IS-IS to communicate with each other. RouterA is a Level-2 router, RouterB is a Level-1-2 router, and RouterC is a Level-1 router. RouterA is heavily loaded because there are too many routing entries on the IS-IS network. Therefore, system resource consumption of RouterA needs to be reduced.
Configuration Roadmap
The configuration roadmap is as follows:
Configure IP addresses for interfaces and enable IS-IS on each router so that the routers can be interconnected.
Configure route summarization on RouterB to reduce the routing table size of RouterA without affecting data forwarding so that the system resource consumption of RouterA can be reduced.
Procedure
- Configure IP addresses for interfaces on each router.
# Configure RouterA.
<Huawei> system-view[Huawei] sysname RouterA[RouterA] interface gigabitethernet 2/0/0[RouterA-GigabitEthernet2/0/0] ip address 172.2.1.1 24[RouterA-GigabitEthernet2/0/0] quitThe configurations of RouterB and RouterC are similar to the configuration of RouterA, and are not mentioned here.
- Configure basic IS-IS functions.
# Configure RouterA.
[RouterA] isis 1[RouterA-isis-1] is-level level-2[RouterA-isis-1] network-entity 20.0000.0000.0001.00[RouterA-isis-1] quit[RouterA] interface gigabitethernet 2/0/0[RouterA-GigabitEthernet2/0/0] isis enable 1[RouterA-GigabitEthernet2/0/0] quit# Configure RouterB.
[RouterB] isis 1[RouterB-isis-1] network-entity 10.0000.0000.0002.00[RouterB-isis-1] quit[RouterB] interface gigabitethernet 2/0/0[RouterB-GigabitEthernet2/0/0] isis enable 1[RouterB-GigabitEthernet2/0/0] quit[RouterB] interface gigabitethernet 1/0/0[RouterB-GigabitEthernet1/0/0] isis enable 1[RouterB-GigabitEthernet1/0/0] quit# Configure RouterC.
[RouterC] isis 1[RouterC-isis-1] is-level level-1[RouterC-isis-1] network-entity 10.0000.0000.0003.00[RouterC-isis-1] quit[RouterC] interface gigabitethernet 1/0/0[RouterC-GigabitEthernet1/0/0] isis enable 1[RouterC-GigabitEthernet1/0/0] quitThe configurations of GigabitEthernet2/0/0, GigabitEthernet3/0/0, and GigabitEthernet4/0/0 are similar to the configuration of GigabitEthernet1/0/0, and are not mentioned here.
- Check the IS-IS routing table of RouterA.
[RouterA] display isis routeRoute information for ISIS(1)
-----------------------------
ISIS(1) Level-2 Forwarding Table
--------------------------------
IPV4 Destination IntCost ExtCost ExitInterface NextHop Flags
----------------------------------------------------------------------------
172.1.1.0/24 30 NULL GE2/0/0 172.2.1.2 A/-/L/-
172.1.2.0/24 30 NULL GE2/0/0 172.2.1.2 A/-/L/-
172.1.3.0/24 30 NULL GE2/0/0 172.2.1.2 A/-/L/-
172.1.4.0/24 20 NULL GE2/0/0 172.2.1.2 A/-/L/-
172.2.1.0/24 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
- Configure route summarization on RouterB.
# Summarize 172.1.1.0/24, 172.1.2.0/24, 172.1.3.0/24, and 172.1.4.0/24 into 172.1.0.0/16 on RouterB.
[RouterB] isis 1[RouterB-isis-1] summary 172.1.0.0 255.255.0.0 level-1-2[RouterB-isis-1] quit - Verify the configuration.
# Check the routing table of RouterA, you can see that routes 172.1.1.0/24, 172.1.2.0/24, 172.1.3.0/24 and 172.1.4.0/24 are summarized into one route 172.1.0.0/16.
[RouterA] display isis routeRoute information for ISIS(1)
-----------------------------
ISIS(1) Level-2 Forwarding Table
--------------------------------
IPV4 Destination IntCost ExtCost ExitInterface NextHop Flags
----------------------------------------------------------------------------
172.1.0.0/16 20 NULL GE2/0/0 172.2.1.2 A/-/L/-
172.2.1.0/24 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
Configuration Files
Configuration file of RouterA
#
sysname RouterA#
isis 1
is-level level-2
network-entity 20.0000.0000.0001.00
#
interface GigabitEthernet2/0/0
ip address 172.2.1.1 255.255.255.0
isis enable 1
#
return
Configuration file of RouterB
#
sysname RouterB#
isis 1
network-entity 10.0000.0000.0002.00
summary 172.1.0.0 255.255.0.0 level-1-2
#
interface GigabitEthernet1/0/0
ip address 172.1.4.2 255.255.255.0
isis enable 1
#
interface GigabitEthernet2/0/0
ip address 172.2.1.2 255.255.255.0
isis enable 1
#
return
Configuration file of RouterC
#
sysname RouterC#
isis 1
is-level level-1
network-entity 10.0000.0000.0003.00
#
interface GigabitEthernet1/0/0
ip address 172.1.4.1 255.255.255.0
isis enable 1
#
interface GigabitEthernet2/0/0
ip address 172.1.1.1 255.255.255.0
isis enable 1
#
interface GigabitEthernet3/0/0
ip address 172.1.2.1 255.255.255.0
isis enable 1
#
interface GigabitEthernet4/0/0
ip address 172.1.3.1 255.255.255.0
isis enable 1
#
return
