Metric
You can make a route the preferred route by changing its metric. In this example, the cost has been configured to make R3 the next hop for R1.
The default metric for each interface is 10. Interface eth3 on R2 has a metric of 20, and Interface eth2 on R3 has a metric of 30. The total cost to reach 10.10.14.0/24 (R4) through R2 and R3 is computed as follows:
R2: 10+20 = 30
R3: 10+30 = 40
In this topology, R1 chooses R2 as its next hop for destination 10.10.14.0/24.
Note: Below configuration is applicable for narrow (non-wide) metric-style. Wide metric can be configured by using the CLI's "metric-style wide" under isis instance and "isis wide-metric < 1-16777214>" under interface mode.
Topology
Figure 13-105:
Configuration
R1
#configure terminal | Enter configure mode. |
(config)#interface eth1 | Enter interface mode. |
(config-if)#ip address 20.20.20.1/24 | Configure IP address on interface. |
(config-if)#ip router isis ABC | Enable IS-IS routing on an interface for area 49 (ABC). |
(config-if)#commit | Commit candidate configuration to the running configuration |
(config-if)#exit | Exit interface mode. |
(config)#interface eth2 | Enter interface mode. |
(config-if)#ip address 30.30.30.1/24 | Configure IP address on interface. |
(config-if)#ip router isis ABC | Enable IS-IS routing on an interface for area 49 (ABC). |
(config-if)#commit | Commit candidate configuration to the running configuration |
(config-if)#exit | Exit interface mode. |
(config)#router isis ABC | Create an IS-IS routing instance for area 49 (ABC). |
(config-router)#is-type level-2-only | Configure instance as level-2-only routing. |
(config-router)#dynamic-hostname | Configure the hostname to be advertised for an ISIS instance. |
(config-router)#net 49.0000.0000.0001.00 | Set a Network Entity Title for this instance, specifying the area address and the system ID. |
(config-router)#commit | Commit candidate configuration to the running configuration |
R2
(config)#interface eth2 | Enter interface mode. |
(config-if)#ip address 30.30.30.2/24 | Configure IP address on interface. |
(config-if)#ip router isis ABC | Enable IS-IS routing on an interface for area 49 (ABC). |
(config-if)#commit | Commit candidate configuration to the running configuration |
(config-if)#exit | Exit interface mode. |
(config)#interface eth3 | Enter interface mode. |
(config-if)#ip address 40.40.40.1/24 | Configure IP address on interface. |
(config-if)#ip router isis ABC | Enable IS-IS routing on an interface for area 49 (ABC). |
(config-if)#commit | Commit candidate configuration to the running configuration |
(config-if)#isis metric 20 | Set the value of IS-IS metric (on eth3) to 20. |
(config-if)#exit | Exit interface mode. |
(config)#router isis ABC | Create an IS-IS routing instance for area 49 (ABC). |
(config-router)#is-type level-2-only | Configure instance as level-2-only routing. |
(config-router)#dynamic-hostname | Configure the hostname to be advertised for an ISIS instance. |
(config-router)#net 49.0000.0000.0002.00 | Set a Network Entity Title for this instance, specifying the area address and the system ID. |
(config-router)#commit | Commit candidate configuration to the running configuration |
R3
(config)#interface eth1 | Enter interface mode. |
(config-if)#ip address 20.20.20.2/24 | Configure IP address on interface. |
(config-if)#ip router isis ABC | Enable IS-IS routing on an interface for area 49 (ABC). |
(config-if)#commit | Commit candidate configuration to the running configuration |
(config-if)#exit | Exit interface mode. |
(config)#interface eth2 | Enter interface mode. |
(config-if)#ip router isis ABC | Enable IS-IS routing on an interface for area 49 (ABC). |
(config-if)#ip address 50.50.50.1/24 | Configure IP address on interface. |
(config-if)#isis metric 30 | Set the value of IS-IS metric (on eth2) to 30. |
(config-if)#commit | Commit candidate configuration to the running configuration |
(config-if)#exit | Exit interface mode. |
(config)#router isis ABC | Create an IS-IS routing instance for area 49 (ABC). |
(config-router)#is-type level-2-only | Configure instance as level-2-only routing. |
(config-router)#dynamic-hostname | Configure the hostname to be advertised for an ISIS instance. |
(config-router)#net 49.0000.0000.0003.00 | Set a Network Entity Title for this instance, specifying the area address and the system ID. |
(config-router)#commit | Commit candidate configuration to the running configuration |
R4
(config)#interface eth1 | Enter interface mode. |
(config-if)#ip router isis ABC | Enable IS-IS routing on an interface for area 49 (ABC). |
(config-if)#ip address 50.50.50.2/24 | Configure IP address on interface. |
(config-if)#commit | Commit candidate configuration to the running configuration |
(config-if)#exit | Exit interface mode. |
(config)#interface eth3 | Enter interface mode. |
(config-if)#ip router isis ABC | Enable IS-IS routing on an interface for area 49 (ABC). |
(config-if)#ip address 40.40.40.2/24 | Configure IP address on interface. |
(config-if)#commit | Commit candidate configuration to the running configuration |
(config-if)#exit | Exit interface mode. |
(config)#router isis ABC | Create an IS-IS routing instance for area 49 (ABC). |
(config-router)#is-type level-2-only | Configure instance as level-2-only routing. |
(config-router)#dynamic-hostname | Configure the hostname to be advertised for an ISIS instance. |
(config-router)#net 49.0000.0000.0004.00 | Set a Network Entity Title for this instance, specifying the area address and the system ID. |
(config-if)#commit | Commit candidate configuration to the running configuration |
Validation
R1#show clns neighbors
Total number of L1 adjacencies: 0
Total number of L2 adjacencies: 2
Total number of adjacencies: 2
Tag ABC: VRF : default
System Id Interface SNPA State Holdtime Type Protocol
R3 eth1 5254.00dc.2f11 Up 5 L2 IS-IS
R2 eth2 5254.007e.5ade Up 20 L2 IS-IS
R2#show clns neighbors
Total number of L1 adjacencies: 0
Total number of L2 adjacencies: 2
Total number of adjacencies: 2
Tag ABC: VRF : default
System Id Interface SNPA State Holdtime Type Protocol
R1 eth2 5254.00a1.6afe Up 7 L2 IS-IS
R4 eth3 5254.00b1.d6fb Up 8 L2 IS-IS
R3#show clns neighbors
Total number of L1 adjacencies: 0
Total number of L2 adjacencies: 2
Total number of adjacencies: 2
Tag ABC: VRF : default
System Id Interface SNPA State Holdtime Type Protocol
R1 eth1 5254.00dc.0b76 Up 20 L2 IS-IS
R4 eth2 5254.00f5.35a4 Up 8 L2 IS-IS
R4#show clns neighbors
Total number of L1 adjacencies: 0
Total number of L2 adjacencies: 2
Total number of adjacencies: 2
Tag ABC: VRF : default
System Id Interface SNPA State Holdtime Type Protocol
R3 eth1 5254.00a8.940d Up 25 L2 IS-IS
R2 eth3 5254.0049.c509 Up 25 L2 IS-IS
R1#show isis topology
Tag ABC: VRF : default
IS-IS paths to level-2 routers
System Id Metric Next-Hop Interface SNPA
R1 --
R2 10 R2 eth2 5254.007e.5ade
R3 10 R3 eth1 5254.00dc.2f11
R4 30 R2 eth2 5254.007e.5ade
R2#show isis topology
Tag ABC: VRF : default
IS-IS paths to level-2 routers
System Id Metric Next-Hop Interface SNPA
R1 10 R1 eth2 5254.00a1.6afe
R2 --
R3 20 R1 eth2 5254.00a1.6afe
R4 20 R4 eth3 5254.00b1.d6fb
R3#show isis topology
Tag ABC: VRF : default
IS-IS paths to level-2 routers
System Id Metric Next-Hop Interface SNPA
R1 10 R1 eth1 5254.00dc.0b76
R2 20 R1 eth1 5254.00dc.0b76
R3 --
R4 30 R4 eth2 5254.00f5.35a4
R4#show isis topology
Tag ABC: VRF : default
IS-IS paths to level-2 routers
System Id Metric Next-Hop Interface SNPA
R1 20 R2 eth3 5254.0049.c509
R3 eth1 5254.00a8.940d
R2 10 R2 eth3 5254.0049.c509
R3 10 R3 eth1 5254.00a8.940d
R4 --
R1#show ip isis route
Codes: C - connected, E - external, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, D - discard, e - external metric
** - invalid
Tag ABC: VRF : default
Destination Metric Next-Hop Interface Tag
C 20.20.20.0/24 10 -- eth1 0
C 30.30.30.0/24 10 -- eth2 0
L2 40.40.40.0/24 30 30.30.30.2 eth2 0
L2 50.50.50.0/24 40 30.30.30.2 eth2 0
20.20.20.2 eth1 0
R2#show ip isis route
Codes: C - connected, E - external, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, D - discard, e - external metric
** - invalid
Tag ABC: VRF : default
Destination Metric Next-Hop Interface Tag
L2 20.20.20.0/24 20 30.30.30.1 eth2 0
C 30.30.30.0/24 10 -- eth2 0
C 40.40.40.0/24 20 -- eth3 0
L2 50.50.50.0/24 30 40.40.40.2 eth3 0
R3#show ip isis route
Codes: C - connected, E - external, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, D - discard, e - external metric
** - invalid
Tag ABC: VRF : default
Destination Metric Next-Hop Interface Tag
C 20.20.20.0/24 10 -- eth1 0
L2 30.30.30.0/24 20 20.20.20.1 eth1 0
L2 40.40.40.0/24 40 20.20.20.1 eth1 0
50.50.50.2 eth2 0
C 50.50.50.0/24 30 -- eth2 0
R4#show ip isis route
Codes: C - connected, E - external, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, D - discard, e - external metric
** - invalid
Tag ABC: VRF : default
Destination Metric Next-Hop Interface Tag
L2 20.20.20.0/24 20 50.50.50.1 eth1 0
L2 30.30.30.0/24 20 40.40.40.1 eth3 0
C 40.40.40.0/24 10 -- eth3 0
C 50.50.50.0/24 10 -- eth1 0
R1#show isis interface
eth1 is up, line protocol is up
Routing Protocol: IS-IS (ABC)
Network Type: Broadcast
Circuit Type: level-1-2
Local circuit ID: 0x01
Extended Local circuit ID: 0x00000003
Local SNPA: 5254.00dc.0b76
IP interface address:
20.20.20.1/24
IPv6 interface address:
fe80::5054:ff:fedc:b76/64
Level-2 Metric: 10/10, Priority: 64, Circuit ID: 0000.0000.0003.01
Number of active level-2 adjacencies: 1
Level-2 LSP MTU: 1492
Next IS-IS LAN Level-2 Hello in 5 seconds
eth2 is up, line protocol is up
Routing Protocol: IS-IS (ABC)
Network Type: Broadcast
Circuit Type: level-1-2
Local circuit ID: 0x02
Extended Local circuit ID: 0x00000004
Local SNPA: 5254.00a1.6afe
IP interface address:
30.30.30.1/24
IPv6 interface address:
fe80::5054:ff:fea1:6afe/64
Level-2 Metric: 10/10, Priority: 64, Circuit ID: 0000.0000.0001.02
Number of active level-2 adjacencies: 1
Level-2 LSP MTU: 1492
Next IS-IS LAN Level-2 Hello in 183 milliseconds
R2#show isis interface
eth2 is up, line protocol is up
Routing Protocol: IS-IS (ABC)
Network Type: Broadcast
Circuit Type: level-1-2
Local circuit ID: 0x01
Extended Local circuit ID: 0x00000004
Local SNPA: 5254.007e.5ade
IP interface address:
30.30.30.2/24
IPv6 interface address:
fe80::5054:ff:fe7e:5ade/64
Level-2 Metric: 10/10, Priority: 64, Circuit ID: 0000.0000.0001.02
Number of active level-2 adjacencies: 1
Level-2 LSP MTU: 1492
Next IS-IS LAN Level-2 Hello in 706 milliseconds
eth3 is up, line protocol is up
Routing Protocol: IS-IS (ABC)
Network Type: Broadcast
Circuit Type: level-1-2
Local circuit ID: 0x02
Extended Local circuit ID: 0x00000005
Local SNPA: 5254.0049.c509
IP interface address:
40.40.40.1/24
IPv6 interface address:
fe80::5054:ff:fe49:c509/64
Level-2 Metric: 20/10, Priority: 64, Circuit ID: 0000.0000.0004.02
Number of active level-2 adjacencies: 1
Level-2 LSP MTU: 1492
Next IS-IS LAN Level-2 Hello in 2 seconds
R3#show isis interface
eth1 is up, line protocol is up
Routing Protocol: IS-IS (ABC)
Network Type: Broadcast
Circuit Type: level-1-2
Local circuit ID: 0x01
Extended Local circuit ID: 0x00000003
Local SNPA: 5254.00dc.2f11
IP interface address:
20.20.20.2/24
IPv6 interface address:
fe80::5054:ff:fedc:2f11/64
Level-2 Metric: 10/10, Priority: 64, Circuit ID: 0000.0000.0003.01
Number of active level-2 adjacencies: 1
Level-2 LSP MTU: 1492
Next IS-IS LAN Level-2 Hello in 2 seconds
eth2 is up, line protocol is up
Routing Protocol: IS-IS (ABC)
Network Type: Broadcast
Circuit Type: level-1-2
Local circuit ID: 0x02
Extended Local circuit ID: 0x00000004
Local SNPA: 5254.00a8.940d
IP interface address:
50.50.50.1/24
IPv6 interface address:
fe80::5054:ff:fea8:940d/64
Level-2 Metric: 30/10, Priority: 64, Circuit ID: 0000.0000.0004.01
Number of active level-2 adjacencies: 1
Level-2 LSP MTU: 1492
Next IS-IS LAN Level-2 Hello in 3 seconds
R4#show isis interface
eth1 is up, line protocol is up
Routing Protocol: IS-IS (ABC)
Network Type: Broadcast
Circuit Type: level-1-2
Local circuit ID: 0x01
Extended Local circuit ID: 0x00000003
Local SNPA: 5254.00f5.35a4
IP interface address:
50.50.50.2/24
IPv6 interface address:
fe80::5054:ff:fef5:35a4/64
Level-2 Metric: 10/10, Priority: 64, Circuit ID: 0000.0000.0004.01
Number of active level-2 adjacencies: 1
Level-2 LSP MTU: 1492
Next IS-IS LAN Level-2 Hello in 0 milliseconds
eth3 is up, line protocol is up
Routing Protocol: IS-IS (ABC)
Network Type: Broadcast
Circuit Type: level-1-2
Local circuit ID: 0x02
Extended Local circuit ID: 0x00000005
Local SNPA: 5254.00b1.d6fb
IP interface address:
40.40.40.2/24
IPv6 interface address:
fe80::5054:ff:feb1:d6fb/64
Level-2 Metric: 10/10, Priority: 64, Circuit ID: 0000.0000.0004.02
Number of active level-2 adjacencies: 1
Level-2 LSP MTU: 1492
Next IS-IS LAN Level-2 Hello in 0 milliseconds
Last modified date: 10/16/2023