- IS-IS Overview and Basic Configuration
- IPv6 Routing: Route Redistribution
- IPv6 Routing: IS-IS Support for IPv6
- Configuring Integrated IS-IS Protocol Shutdown Support Maintaining Configuration Parameters
- Customizing IS-IS for Your Network Design
- IS-IS MIB
- IS-IS Support for an IS-IS Instance per VRF for IP
- Overview of IS-IS Fast Convergence
- Setting Best Practice Parameters for IS-IS Fast Convergence
- Reducing Failure Detection Times in IS-IS Networks
- IPv6 Routing: IS-IS Multitopology Support for IPv6
- Reducing Link Failure and Topology Change Notification Times in IS-IS Networks
- IS-IS Support for Route Tags
- Enhancing Security in an IS-IS Network
- IS-IS IPv6 Administrative Tag
- IS-IS IPv6 Advertise Passive Only
- IS-IS IPv6 Multi-Process Support
- ISIS Local Microloop Protection
Contents
- Customizing IS-IS for Your Network Design
- Finding Feature Information
- Prerequisites for Customizing IS-IS for Your Network Design
- Information About Customizing IS-IS for Your Network Design
- Enhancing Your IS-IS Network Design at the Interface Level
- Setting the IS-IS Link-State Metrics
- Prioritizing Designated Intermediate Systems for IS-IS
- Enhancing Your IS-IS Network Design at the Router Level
- Limiting Level 1 and Level 2 Operations on the IS-IS Router
- Summarizing Address Ranges in the IS-IS Routing Table
- Generating an IS-IS Default Route
- Configuring an IS-IS Default Metric
- Configuration Examples for Customizing IS-IS for Your Network Design
- Example Configuring a Global Default Metric for IPv4
- Additional References
- Feature Information for Customizing IS-IS for Your Network Design
Customizing IS-IS for Your Network Design
This module describes optional tasks that you can perform to customize Intermediate System-to-Intermediate System (IS-IS) for your network design. You can optimize network traffic flow by setting metrics, specifying an IS-IS system type, summarizing addresses, generating a default route, and configuring a global default metric.
- Finding Feature Information
- Prerequisites for Customizing IS-IS for Your Network Design
- Information About Customizing IS-IS for Your Network Design
- Configuration Examples for Customizing IS-IS for Your Network Design
- Additional References
- Feature Information for Customizing IS-IS for Your Network Design
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Prerequisites for Customizing IS-IS for Your Network Design
Before performing the tasks in this module, you should be familiar with the concepts described in the "Integrated IS-IS Routing Protocol Overview" module.
You should understand the concept of IP addressing. For more information on IP addressing, see the "Configuring IPv4 Addresses" chapter of the Cisco IOS XE IP Addressing Services Configuration Guide, Release 2.
You should know your network design and how you want traffic to flow through it before configuring IS-IS. Define areas, prepare an addressing plan for the routers (including defining the network entity titles [NETs]), and determine the interfaces that will run Integrated IS-IS.
IS-IS must be enabled.
Information About Customizing IS-IS for Your Network Design
You can enhance network traffic flow by configuring IS-IS metric values for Level-1 or Level-2 routing, in order to prioritize traffic through certain paths. You can customize network traffic flow by changing the metric cost for a specified interface. All IS-IS links use the metric of 10 by default. The protocol does not automatically incorporate link attributes such as bandwidth or delay when metric values are assigned. The total cost to a destination is the sum of the costs on all outgoing interfaces along a particular path from the source to the destination. The least-cost paths are preferred.
On multi-access networks, IS-IS elects a router to act as a pseudo-node representing the multi-access circuit. The elected router is known as the designated intermediate system (DIS). The DIS issues pseudo-node LSPs listing all of the routers which are reachable on the network. Each router on the network advertises in its non-pseudonode LSPs reachability to the DIS. This reduces the amount of information that needs to be advertised. A DIS is elected for each level that is operating on the network, for example both Level 1 and Level 2. By default, all routers have the same priority for being elected DIS. The MAC address of each router’s interface onto the network is used as the tiebreaker. When all routers have the same priority, the addition or removal of a router onto the network can result in a chance in the DIS. This churn can be prevented by assigning a higher priority to the router which you wish to act as the DIS. Priorities can be configured individually for Level 1 and Level 2. By default the priority is 64. You can configure the priority in the range from 0 to 127.
You can configure a summary address to represent summarized (aggregate) addresses within the IS-IS routing table. This process is called route summarization. Using a summary address can enhance scalability and network stability because it reduces the amount of information that needs to be advertised and reduces the frequency of updates required. For example, a single route flap may not cause the summary advertisement to flap. The disadvantage of using the summary addresses is that routing may be sub-optimal, for example, the path to a specific destination covered by the summary address may be longer than it would have been, had all the individual addresses been advertised. Summary addresses are most commonly used to summarize routes from one Level-one area into the Level-2 subdomain. One summary address can include multiple groups of addresses for a given level. Routes learned from other routing protocols can also be summarized. The metric used to advertise the summary is the smallest metric of all the more-specific routes.
Whenever you specifically configure redistribution of routes into an IS-IS routing domain, the Cisco IOS XE software does not, by default, redistribute the default route into the IS-IS routing domain. If you wish to advertise a default route you must use the default-information originate command. This command causes a default route to be advertised by the router. Advertisement of the default route can be made conditional by using a route map. You can use the route map to identify the level into which the default route is to be announced, whether a particular non-default prefix must be reachable, etc.
In Cisco IOS XE software, IS-IS has a default metric value of 10 for all active interfaces. If the interface is passive, the default value is zero. Rather than change the metric values for the active interfaces one by one, you can configure a different default metric value to be used by all interfaces. All interfaces that had the original IS-IS default metric 10 will be configured with the new default value. Besides offering the user the convenience of being able to globally configure the value for all IS-IS interfaces, the feature helps prevent errors that may occur when interfaces are individually configured to change the metric value. For example the user may remove configured metrics from an interface, thereby restoring the default metric value of 10--perhaps unintentionally making that interface a highly preferred one in the network. Such an occurrence on the wrong interface could mean the rerouting of traffic across the network on an undesirable path.
- Enhancing Your IS-IS Network Design at the Interface Level
- Enhancing Your IS-IS Network Design at the Router Level
Enhancing Your IS-IS Network Design at the Interface Level
Setting the IS-IS Link-State Metrics
1.
enable
2.
configure
terminal
3.
interface
type
name
4.
isis
metric
default-metric
[level-1 | level-2]
5.
end
6.
show
isis
[process-tag] database [level-1] [level-2] [l1] [l2] [detail] [lspid]
DETAILED STEPS
Prioritizing Designated Intermediate Systems for IS-IS
1.
enable
2.
configure
terminal
3.
interface
type
name
4.
isis
priority
number-value
[level-1 | level-2]
5.
end
DETAILED STEPS
| Command or Action | Purpose | |
|---|---|---|
| Step 1 |
enable
Example: Router> enable |
Enables privileged EXEC mode.
|
| Step 2 |
configure
terminal
Example: Router# configure terminal |
Enters global configuration mode. |
| Step 3 |
interface
type
name
Example: Router(config)# interface gigabitethernet 0/3/0 |
Enters interface configuration mode. |
| Step 4 |
isis
priority
number-value
[level-1 | level-2] Example: Router(config-if)# isis priority 2 level-1 |
Configures the priority used in the designated router election. |
| Step 5 |
end
Example: Router(config-if)# end |
Exits interface configuration mode and returns to privileged EXEC mode. |
Enhancing Your IS-IS Network Design at the Router Level
- Limiting Level 1 and Level 2 Operations on the IS-IS Router
- Summarizing Address Ranges in the IS-IS Routing Table
- Generating an IS-IS Default Route
- Configuring an IS-IS Default Metric
Limiting Level 1 and Level 2 Operations on the IS-IS Router
1.
enable
2.
configure
terminal
3.
router
isis
area-tag
4.
is-type
{level-1 |
level-1-2 |
level-2-only}
5.
end
6.
show
isis
[ipv6] [*]
topology[level-1] [level-2]
DETAILED STEPS
| Command or Action | Purpose | |||
|---|---|---|---|---|
| Step 1 |
enable
Example: Router> enable |
Enables privileged EXEC mode. | ||
| Step 2 |
configure
terminal
Example: Router# configure terminal |
Enters global configuration mode. | ||
| Step 3 |
router
isis
area-tag
Example: Router(config)# router isis 1 |
Enables IS-IS as an IP routing protocol. | ||
| Step 4 |
is-type
{level-1 |
level-1-2 |
level-2-only}
Example: Router(config-router)# is-type level-1 |
Configures the routing level for an instance of the IS-IS routing process.
| ||
| Step 5 |
end
Example: Router(config-router)# end |
Exits router configuration mode and returns to privileged EXEC mode. | ||
| Step 6 |
show
isis
[ipv6] [*]
topology[level-1] [level-2]
Example: Router# show isis topology level-1 |
(Optional) Displays a list of all connected routers in all areas. |
Examples
The following example shows output from the show isis topology command for a router within a dual CLNS-IP network. In this example, because neither the level-1 nor level-2 optional keywords were entered, information is displayed for both Level 1 and Level 2 routers.
Router# show isis topology Tag L2BB: IS-IS paths to level-2 routers System Id Metric Next-Hop Interface SNPA 0000.0000.0005 -- 0000.0000.0009 10 0000.0000.0009 Tu529 *Tunnel* 0000.0000.0017 20 0000.0000.0009 Tu529 *Tunnel* 0000.0000.0053 30 0000.0000.0009 Tu529 *Tunnel* 0000.0000.0068 20 0000.0000.0009 Tu529 *Tunnel* Tag A3253-01: IS-IS paths to level-1 routers System Id Metric Next-Hop Interface SNPA 0000.0000.0003 10 0000.0000.0003 FE1/0/0 0000.0c03.6944 0000.0000.0005 -- 0000.0000.0053 10 0000.0000.0053 FE1 /0/0 0060.3e58.ccdb
Summarizing Address Ranges in the IS-IS Routing Table
1.
enable
2.
configure
terminal
3.
router
isis
area-tag
4.
summary-address
address
mask
{level-1 | level-1-2 | level-2}[tag tag-number] [metric metric-value]
5.
end
6.
show
isis
database
verbose
DETAILED STEPS
| Command or Action | Purpose | |||
|---|---|---|---|---|
| Step 1 |
enable
Example: Router> enable |
Enables privileged EXEC mode.
| ||
| Step 2 |
configure
terminal
Example: Router# configure terminal |
Enters global configuration mode. | ||
| Step 3 |
router
isis
area-tag
Example: Router(config)# router isis 1 |
Enables IS-IS as an IP routing protocol.
| ||
| Step 4 |
summary-address
address
mask
{level-1 | level-1-2 | level-2}[tag tag-number] [metric metric-value] Example: Router(config-router)# summary-address 10.1.0.0 255.255.0.0 level-2 |
Creates aggregate addresses for IS-IS.
| ||
| Step 5 |
end
Example: Router(config-router)# end |
Exits router configuration mode and returns to privileged EXEC mode. | ||
| Step 6 |
show
isis
database
verbose
Example: Router# show isis database verbose |
(Optional) Displays detailed information about the IS-IS database. |
Generating an IS-IS Default Route
1.
enable
2.
configure
terminal
3.
router
isis
area-tag
4.
default-information
originate
[route-map map-name]
5.
end
6.
show
ip
route
DETAILED STEPS
| Command or Action | Purpose | |
|---|---|---|
| Step 1 |
enable
Example: Router> enable |
Enables privileged EXEC mode.
|
| Step 2 |
configure
terminal
Example: Router# configure terminal |
Enters global configuration mode. |
| Step 3 |
router
isis
area-tag
Example: Router(config)# router isis 1 |
Enables IS-IS as an IP routing protocol.
|
| Step 4 |
default-information
originate
[route-map map-name] Example: Router(config-router)# default-information originate |
Generates a default route into an IS-IS routing domain. |
| Step 5 |
end
Example: Router(config-router)# end |
Exits router configuration mode and returns to privileged EXEC mode. |
| Step 6 |
show
ip
route
Example: Router# show ip route |
(Optional) Displays the current state of the routing table. |
Configuring an IS-IS Default Metric
 Note | If you have already configured a metric for a specific interface by entering the isis metric command, the metric that has been configured for that specific interface will take precedence over any default set by the metric command. |
1.
enable
2.
configure
terminal
3.
router
isis
area-tag
4.
metric
default-value
[level-1 | level-2]
5.
end
DETAILED STEPS
| Command or Action | Purpose | |
|---|---|---|
| Step 1 |
enable
Example: Router> enable |
Enables privileged EXEC mode.
|
| Step 2 |
configure
terminal
Example: Router# configure terminal |
Enters global configuration mode. |
| Step 3 |
router
isis
area-tag
Example: Router(config)# router isis 1 |
Enables IS-IS as an IP routing protocol.
|
| Step 4 |
metric
default-value
[level-1 | level-2] Example: Router(config-router)# metric 25 level-2 |
Globally sets a new default metric value for all IS-IS interfaces.
|
| Step 5 |
end
Example: Router(config-router)# end |
Exits router configuration mode and returns to privileged EXEC mode. |
Configuration Examples for Customizing IS-IS for Your Network Design
Example Configuring a Global Default Metric for IPv4
The following configuration example for an IS-IS routing process called area1 sets a global default metric of 111 for the IS-IS interfaces:
interface gigabitethernet3/1/0 ip address 172.16.10.2 255.255.0.0 ip router isis area1 no ip route-cache duplex half ! interface gigabitethernet3/2/0 ip address 192.168.242.2 255.255.255.0 ip router isis area1 no ip route-cache duplex half router isis area1 net 01.0000.0309.1234.00 metric-style wide metric 111
In the following example, the show clns interface command confirms that the IS-IS IPv4 interface metric for both Level 1 and Level 2 interfaces is assigned the new default metric value 111:
Router# show clns interface
GigabitEthernet3/1/0 is up, line protocol is up
Checksums enabled, MTU 1497, Encapsulation SAP
ERPDUs enabled, min. interval 10 msec.
CLNS fast switching enabled
CLNS SSE switching disabled
DEC compatibility mode OFF for this interface
Next ESH/ISH in 39 seconds
Routing Protocol: IS-IS
Circuit Type: level-1-2
Interface number 0x0, local circuit ID 0x1
Level-1 Metric: 111, Priority: 64, Circuit ID: mekong.01
Level-1 IPv6 Metric: 10
Number of active level-1 adjacencies: 0
Level-2 Metric: 111, Priority: 64, Circuit ID: mekong.01
Level-2 IPv6 Metric: 10
Number of active level-2 adjacencies: 0
Next IS-IS LAN Level-1 Hello in 922 milliseconds
Next IS-IS LAN Level-2 Hello in 1 seconds
GigabitEthernet3/2/0 is up, line protocol is up
Checksums enabled, MTU 1497, Encapsulation SAP
ERPDUs enabled, min. interval 10 msec.
CLNS fast switching enabled
CLNS SSE switching disabled
DEC compatibility mode OFF for this interface
Next ESH/ISH in 20 seconds
Routing Protocol: IS-IS
Circuit Type: level-1-2
Interface number 0x1, local circuit ID 0x2
Level-1 Metric: 111, Priority: 64, Circuit ID: mekong.02
Level-1 IPv6 Metric: 10
Number of active level-1 adjacencies: 1
Level-2 Metric: 111, Priority: 64, Circuit ID: mekong.02
Level-2 IPv6 Metric: 10
Number of active level-2 adjacencies: 1
Next IS-IS LAN Level-1 Hello in 2 seconds
Next IS-IS LAN Level-2 Hello in 1 seconds
In the following example, the isis metric command is entered so that it will assign a metric value of 10. The metric value that is set with the isis metric command for GigabitEthernet interface 3/1/0 will take precedence over the metric value that was previously set with the metric command.
interface GigabitEthernet3/1/0 ip address 172.30.10.2 255.255.0.0 ip router isis area1 no ip route-cache duplex half isis metric 10 ! interface GigabitEthernet3/2/0 ip address 192.168.224.2 255.255.255.0 ip router isis area1 no ip route-cache duplex half router isis area1 net 01.0000.0309.1234.00 metric-style wide metric 111
When the show clns interfacecommand is entered, the router output confirms that the interface has an assigned IS-IS IPv4 metric value of 10:
Router# show clns interface
GigabitEthernet3/1/0 is up, line protocol is up
Checksums enabled, MTU 1497, Encapsulation SAP
ERPDUs enabled, min. interval 10 msec.
CLNS fast switching enabled
CLNS SSE switching disabled
DEC compatibility mode OFF for this interface
Next ESH/ISH in 53 seconds
Routing Protocol: IS-IS
Circuit Type: level-1-2
Interface number 0x0, local circuit ID 0x1
Level-1 Metric: 10, Priority: 64, Circuit ID: mekong.01
Level-1 IPv6 Metric: 10
Number of active level-1 adjacencies: 0
Level-2 Metric: 10, Priority: 64, Circuit ID: mekong.01
Level-2 IPv6 Metric: 10
Number of active level-2 adjacencies: 0
Next IS-IS LAN Level-1 Hello in 4 seconds
Next IS-IS LAN Level-2 Hello in 4 seconds
GigabitEthernet3/2/0 is up, line protocol is up
Checksums enabled, MTU 1497, Encapsulation SAP
ERPDUs enabled, min. interval 10 msec.
CLNS fast switching enabled
CLNS SSE switching disabled
DEC compatibility mode OFF for this interface
Next ESH/ISH in 30 seconds
Routing Protocol: IS-IS
Circuit Type: level-1-2
Interface number 0x1, local circuit ID 0x2
Level-1 Metric: 111, Priority: 64, Circuit ID: mekong.02
Level-1 IPv6 Metric: 10
Number of active level-1 adjacencies: 1
Level-2 Metric: 111, Priority: 64, Circuit ID: mekong.02
Level-2 IPv6 Metric: 10
Number of active level-2 adjacencies: 1
Next IS-IS LAN Level-1 Hello in 2 seconds
Next IS-IS LAN Level-2 Hello in 922 milliseconds
Additional References
Related Documents
|
Related Topic |
Document Title |
|---|---|
|
IS-IS commands: complete command syntax, command mode, defaults, command history, usage guidelines, and examples |
Cisco IOS IP Routing: ISIS Command Reference |
|
Overview of Integrated IS-IS conceptual information with links to all the individual IS-IS modules |
"Integrated IS-IS Routing Protocol Overview" module |
|
Configuring IPv6 |
"Implementing IPv6 Addressing and Basic Connectivity" chapter in the Cisco IOS IPv6 XE Configuration Guide, Release 2 |
|
Configuring the IS-IS protocol for IPv6 networks |
"Implementing IS-IS for IPv6" module in the Cisco IOS XE IPv6 Configuration Guide , Release 2 |
|
Customizing IS-IS for fast convergence and scalability |
"Overview of IS-IS Fast Convergence" module |
|
Enhancing IS-IS network security |
"Enhancing Security in an IS-IS Network" module |
|
Cisco IOS master command list, all releases |
Standards
|
Standard |
Title |
|---|---|
|
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature. |
-- |
MIBs
|
MIB |
MIBs Link |
|---|---|
|
No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature. |
To locate and download MIBs for selected platforms, Cisco IOS XE software releases, and feature sets, use Cisco MIB Locator found at the following URL: |
RFCs
|
RFCs |
Title |
|---|---|
|
RFC 1195 |
s |
Technical Assistance
|
Description |
Link |
|---|---|
|
The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password. |
Feature Information for Customizing IS-IS for Your Network Design
The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
|
Feature Name |
Releases |
Feature Information |
|---|---|---|
|
Integrated IS-IS Global Default Metric |
Cisco IOS XE Release 2.1 |
The Integrated IS-IS Global Default Metric feature allows you to change the global IS-IS default metric for interfaces so that you need not change the metric values for the interfaces one by one. All interfaces that had the original IS-IS default metric 10 will be configured with the new global default value. This feature was introduced on the Cisco ASR 1000 Series Aggregation Services Routers. The following commands were modified by this feature: metric, router isis. |