This documentation has been moved
Integrated IS-IS Features Roadmap
Downloads: This chapterpdf (PDF - 185.0KB) The complete bookPDF (PDF - 1.14MB) | Feedback

Integrated IS-IS Features Roadmap

Table Of Contents

Integrated IS-IS Features Roadmap


Integrated IS-IS Features Roadmap


First Published: April 30, 2007
Last Updated: September 10, 2010

This roadmap lists the features documented in the Cisco IOS IP Routing: ISIS Configuration Guide and maps them to the modules in which they appear.

Feature and Release Support

Table 1 lists Integrated IS-IS feature support for the following Cisco IOS software release trains:

Cisco IOS Release 12.0S

Cisco IOS Release 12.2S

Cisco IOS Release 12.2SB

Cisco IOS Release 12.2SR

Cisco IOS Release 12.2SX

Cisco IOS Releases 12.2T, 12.3, 12.3T, 12.4, and 12.4T

Cisco IOS Release 15.0M

Cisco IOS Release XE 3.1.0SG

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.


Note Table 1 lists only the Cisco IOS software release that introduced support for a given feature in a given Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS software release train also support that feature.


Table 1 Supported Integrated IS-IS Features 

Release
Feature Name
Feature Description
Where Documented
Cisco IOS Release 12.0S

12.0(29)S

IS-IS Support for an IS-IS Instance per VRF for IP

The IS-IS Support for an IS-IS Instance per VRF for IP feature provides multiple VPN routing and forwarding (VRF)-aware Intermediate System-to-Intermediate System (IS-IS) instances. The VRF functionality allows Internet service providers (ISPs) to separate routing protocol information and propagate it to the appropriate routing table and network neighbors. Using one router with VRF functionality is more cost-effective than using separate routers to separate and forward the routing information.

IS-IS Support for an IS-IS Instance per VRF for IP

12.0(27)S

Integrated IS-IS Global Default Metric

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 default value.

Customizing IS-IS for Your Network Design

Integrated IS-IS Protocol Shutdown Support Maintaining Configuration Parameters

This feature allows you to disable the Integrated IS-IS protocol at the interface level or at the global IS-IS process level without removing the IS-IS configuration parameters.

Configuring a Basic IS-IS Network

IS-IS Caching of Redistributed Routes

The IS-IS Caching of Redistributed Routes feature improves IS-IS convergence time when routes are being redistributed into IS-IS. This feature introduces new commands for monitoring and maintaining IS-IS redistributed routes.

Reducing Alternate-Path Calculation Times in IS-IS Networks

IS-IS Fast-Flooding of LSPs Using the fast-flood Command

The IS-IS Fast-Flooding of LSPs Using the fast-flood Command feature improves IS-IS convergence time when new link-state PDUs (LSPs) are generated in the network and shortest path first (SPF) is triggered by the new LSPs. This feature introduces the new fast-flood command.

Reducing Link Failure and Topology Change Notification Times in IS-IS Networks

12.0(26)S

IS-IS Support for Priority-Driven IP Prefix RIB Installation

The IS-IS Support for Priority-Driven IP Prefix RIB Installation feature allows customers to designate a subset of IP prefixes advertised by Integrated IS-IS for faster processing and installation in the global routing table as one way to achieve faster convergence. For example, Voice over IP (VoIP) gateway addresses may need to be processed first to help VoIP traffic get updated faster than other types of packets.

Reducing Alternate-Path Calculation Times in IS-IS Networks

12.0(25)S

IS-IS Limit on Number of Redistributed Routes

The IS-IS Limit on Number of Redistributed Routes feature provides for a user-defined maximum number of prefixes that are allowed to be redistributed into IS-IS from other protocols or other IS-IS processes. Such a limit could help prevent the router from being flooded by too many redistributed routes.

Reducing Alternate-Path Calculation Times in IS-IS Networks

12.0(24)S

IS-IS Incremental SPF

Integrated IS-IS can be configured to use an incremental SPF algorithm for calculating the shortest path first routes. Incremental SPF is more efficient than the full SPF algorithm, thereby allowing IS-IS to converge faster on a new routing topology in reaction to a network event.

Reducing Alternate-Path Calculation Times in IS-IS Networks

12.0(22)S

IS-IS HMAC-MD5 Authentication and Enhanced Clear Text Authentication

The IS-IS HMAC-MD5 authentication feature adds an HMAC-MD5 digest to each IS-IS protocol data unit (PDU). The digest allows authentication at the IS-IS routing protocol level, which prevents unauthorized routing message from being injected into the network routing domain. IS-IS clear text (plain text) authentication is enhanced so that passwords are encrypted when the software configuration is displayed and passwords are easier to manage and change.

Enhancing Security in an IS-IS Network

IS-IS Mechanisms to Exclude Connected IP Prefixes from LSP Advertisements

Beginning with Cisco IOS Release 12.0(22)S, IS-IS caches routes that are redistributed from other routing protocols or from another IS-IS level into a local redistribution cache that is maintained by IS-IS. Caching occurs automatically and requires no configuration. The caching of redistributed routes improves IS-IS convergence time when routes are being redistributed into IS-IS. IS-IS caching of redistributed routes increases the performance of LSP generation, significantly improving network scalability.

Reducing Alternate-Path Calculation Times in IS-IS Networks

Cisco IOS Release 12.2S

12.2(25)S

Integrated IS-IS Global Default Metric

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 of 10 will be configured with the new default value.

Customizing IS-IS for Your Network Design

12.2(25)S

Integrated IS-IS Protocol Shutdown Support Maintaining Configuration Parameters

This feature allows you to disable the Integrated IS-IS protocol at the interface level or at the global IS-IS process level without removing the IS-IS configuration parameters.

Configuring a Basic IS-IS Network

12.2(25)S

IS-IS Caching of Redistributed Routes

The IS-IS Caching of Redistributed Routes feature improves IS-IS convergence time when routes are being redistributed into IS-IS. This feature introduces new commands for monitoring and maintaining IS-IS redistributed routes.

Reducing Alternate-Path Calculation Times in IS-IS Networks

12.2(25)S

IS-IS Support for Priority-Driven IP Prefix RIB Installation

The IS-IS Support for Priority-Driven IP Prefix RIB Installation feature allows customers to designate a subset of IP prefixes advertised by Integrated IS-IS for faster processing and installation in the global routing table as one way to achieve faster convergence. For example, Voice over IP (VoIP) gateway addresses may need to be processed first to help VoIP traffic get updated faster than other types of packets.

Reducing Alternate-Path Calculation Times in IS-IS Networks

12.2(18)S

IS-IS Incremental SPF

Integrated IS-IS can be configured to use an incremental SPF algorithm for calculating the shortest path first routes. Incremental SPF is more efficient than the full SPF algorithm, thereby allowing IS-IS to converge faster on a new routing topology in reaction to a network event.

Reducing Alternate-Path Calculation Times in IS-IS Networks

IS-IS Limit on Number of Redistributed Routes

The IS-IS Limit on Number of Redistributed Routes feature provides for a user-defined maximum number of prefixes that are allowed to be redistributed into IS-IS from other protocols or other IS-IS processes. Such a limit could help prevent the router from being flooded by too many redistributed routes.

Reducing Alternate-Path Calculation Times in IS-IS Networks

IS-IS Mechanisms to Exclude Connected IP Prefixes from LSP Advertisements

Beginning with Cisco IOS Release 12.0(22)S, IS-IS caches routes that are redistributed from other routing protocols or from another IS-IS level into a local redistribution cache that is maintained by IS-IS. Caching occurs automatically and requires no configuration. The caching of redistributed routes improves IS-IS convergence time when routes are being redistributed into IS-IS. IS-IS caching of redistributed routes increases the performance of LSP generation, significantly improving network scalability.

Reducing Alternate-Path Calculation Times in IS-IS Networks

IS-IS Support for Route Tags

The IS-IS Support for Route Tags feature provides the capability to tag IS-IS route prefixes and use those tags in a route map to control IS-IS route redistribution or route leaking.

Reducing Alternate-Path Calculation Times in IS-IS Networks

12.2(11)S

IS-IS HMAC-MD5 Authentication and Enhanced Clear Text Authentication

The IS-IS HMAC-MD5 authentication feature adds an HMAC-MD5 digest to each IS-IS protocol data unit (PDU). The digest allows authentication at the IS-IS routing protocol level, which prevents unauthorized routing message from being injected into the network routing domain. IS-IS clear text (plain text) authentication is enhanced so that passwords are encrypted when the software configuration is displayed and passwords are easier to manage and change.

Enhancing Security in an IS-IS Network

Cisco IOS Release 12.2SB

12.2(31)SB3

IS-IS MIB

The IS-IS MIB feature introduces MIB support for the IS-IS link-state routing protocol. IS-IS is used as the link-state routing protocol of choice by major service providers. The IS-IS MIB feature offers service providers an improved capability to continuously monitor the changing state of an IS-IS network by use of MIB objects to gather information relating to protocol parameters and trap notification objects that can signal the occurrence of significant protocol events such as an authentication failure or a mismatch in area addresses between Intermediate Systems (ISs). The protocol information collected by the IS-IS MIB objects and trap objects can be used by the network manager to derive statistics that can help monitor and improve overall network performance.

In 12.2(31)SB2, this feature was implemented on the Cisco 7000 series routers.

In 12.2(31)SB3, this feature was implemented on the Cisco 10000 series routers.

IS-IS MIB

12.2(31)SB2

IS-IS MIB

The IS-IS MIB feature introduces MIB support for the IS-IS link-state routing protocol. IS-IS is used as the link-state routing protocol of choice by major service providers. The IS-IS MIB feature offers service providers an improved capability to continuously monitor the changing state of an IS-IS network by use of MIB objects to gather information relating to protocol parameters and trap notification objects that can signal the occurrence of significant protocol events such as an authentication failure or a mismatch in area addresses between Intermediate Systems (ISs). The protocol information collected by the IS-IS MIB objects and trap objects can be used by the network manager to derive statistics that can help monitor and improve overall network performance.

In 12.2(31)SB2, this feature was implemented on the Cisco 7000 series routers.

IS-IS MIB

12.2(27)SBC

Integrated IS-IS Global Default Metric

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 of 10 will be configured with the new default value.

Customizing IS-IS for Your Network Design

12.2(27)SBC

Integrated IS-IS Protocol Shutdown Support Maintaining Configuration Parameters

This feature allows you to disable the Integrated IS-IS protocol at the interface level or at the global IS-IS process level without removing the IS-IS configuration parameters.

Configuring a Basic IS-IS Network

12.2(27)SBC

IS-IS Incremental SPF

Integrated IS-IS can be configured to use an incremental SPF algorithm for calculating the shortest path first routes. Incremental SPF is more efficient than the full SPF algorithm, thereby allowing IS-IS to converge faster on a new routing topology in reaction to a network event.

Reducing Alternate-Path Calculation Times in IS-IS Networks

12.2(27)SBC

IS-IS Limit on Number of Redistributed Routes

The IS-IS Limit on Number of Redistributed Routes feature provides for a user-defined maximum number of prefixes that are allowed to be redistributed into IS-IS from other protocols or other IS-IS processes. Such a limit could help prevent the router from being flooded by too many redistributed routes.

Reducing Alternate-Path Calculation Times in IS-IS Networks

12.2(27)SBC

IS-IS Mechanisms to Exclude Connected IP Prefixes from LSP Advertisements

Beginning with Cisco IOS Release 12.0(22)S, IS-IS caches routes that are redistributed from other routing protocols or from another IS-IS level into a local redistribution cache that is maintained by IS-IS. Caching occurs automatically and requires no configuration. The caching of redistributed routes improves IS-IS convergence time when routes are being redistributed into IS-IS. IS-IS caching of redistributed routes increases the performance of LSP generation, significantly improving network scalability.

Reducing Alternate-Path Calculation Times in IS-IS Networks

12.2(27)SBC

IS-IS Support for Priority-Driven IP Prefix RIB Installation

The IS-IS Support for Priority-Driven IP Prefix RIB Installation feature allows customers to designate a subset of IP prefixes advertised by Integrated IS-IS for faster processing and installation in the global routing table as one way to achieve faster convergence. For example, Voice over IP (VoIP) gateway addresses may need to be processed first to help VoIP traffic get updated faster than other types of packets.

Reducing Alternate-Path Calculation Times in IS-IS Networks

12.2(27)SBC

IS-IS Support for Route Tags

The IS-IS Support for Route Tags feature provides the capability to tag IS-IS route prefixes and use those tags in a route map to control IS-IS route redistribution or route leaking.

Reducing Alternate-Path Calculation Times in IS-IS Networks

Cisco IOS Release 12.2SR

12.2(33)SRB

IS-IS MIB

The IS-IS MIB feature introduces MIB support for the IS-IS link-state routing protocol. IS-IS is used as the link-state routing protocol of choice by major service providers. The IS-IS MIB feature offers service providers an improved capability to continuously monitor the changing state of an IS-IS network by use of MIB objects to gather information relating to protocol parameters and trap notification objects that can signal the occurrence of significant protocol events such as an authentication failure or a mismatch in area addresses between Intermediate Systems (ISs). The protocol information collected by the IS-IS MIB objects and trap objects can be used by the network manager to derive statistics that can help monitor and improve overall network performance.

In 12.2(31)SB2, this feature was implemented on the Cisco 7000 series routers.

In 12.2(31)SB3, this feature was implemented on the Cisco 10000 series routers.

IS-IS MIB

12.2(33)SRB

IS-IS Support for an IS-IS Instance per VRF for IP

The IS-IS Support for an IS-IS Instance per VRF for IP feature provides multiple VPN routing and forwarding (VRF)-aware Intermediate System-to-Intermediate System (IS-IS) instances. The VRF functionality allows Internet service providers (ISPs) to separate routing protocol information and propagate it to the appropriate routing table and network neighbors. Using one router with VRF functionality is more cost-effective than using separate routers to separate and forward the routing information.

IS-IS Support for an IS-IS Instance per VRF for IP

12.2(33)SRA

IS-IS Support for Priority-Driven IP Prefix RIB Installation

The IS-IS Support for Priority-Driven IP Prefix RIB Installation feature allows customers to designate a subset of IP prefixes advertised by Integrated IS-IS for faster processing and installation in the global routing table as one way to achieve faster convergence. For example, Voice over IP (VoIP) gateway addresses may need to be processed first to help VoIP traffic get updated faster than other types of packets.

Reducing Alternate-Path Calculation Times in IS-IS Networks

Cisco IOS Release 12.2SX

12.2(18)SXE

Integrated IS-IS Global Default Metric

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 of 10 will be configured with the new default value.

Customizing IS-IS for Your Network Design

Cisco IOS Releases 12.2T, 12.3, 12.3T, 12.4, and 12.4T

12.3(7)T

IS-IS Caching of Redistributed Routes

The IS-IS Caching of Redistributed Routes feature improves IS-IS convergence time when routes are being redistributed into IS-IS. This document introduces new commands for monitoring and maintaining IS-IS redistributed routes.

Reducing Alternate-Path Calculation Times in IS-IS Networks

IS-IS Fast-Flooding of LSPs Using the fast-flood Command

The IS-IS Fast-Flooding of LSPs Using the fast-flood Command feature improves IS-IS convergence time when new link-state PDUs (LSPs) are generated in the network and shortest path first (SPF) is triggered by the new LSPs. This feature introduces the new fast-flood command.

Reducing Link Failure and Topology Change Notification Times in IS-IS Networks

12.3(4)T

Integrated IS-IS Global Default Metric

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 default value.

Customizing IS-IS for Your Network Design

Integrated IS-IS Protocol Shutdown Support Maintaining Configuration Parameters

This feature allows you to disable the Integrated IS-IS protocol at the interface level or at the global IS-IS process level without removing the IS-IS configuration parameters.

Configuring a Basic IS-IS Network

IS-IS Limit on Number of Redistributed Routes

The IS-IS Limit on Number of Redistributed Routes feature provides for a user-defined maximum number of prefixes that are allowed to be redistributed into IS-IS from other protocols or other IS-IS processes. Such a limit could help prevent the router from being flooded by too many redistributed routes.

Reducing Alternate-Path Calculation Times in IS-IS Networks

IS-IS Support for Priority-Driven IP Prefix RIB Installation

The IS-IS Support for Priority-Driven IP Prefix RIB Installation feature allows customers to designate a subset of IP prefixes advertised by Integrated IS-IS for faster processing and installation in the global routing table as one way to achieve faster convergence. For example, Voice over IP (VoIP) gateway addresses may need to be processed first to help VoIP traffic get updated faster than other types of packets.

Reducing Alternate-Path Calculation Times in IS-IS Networks

12.3(2)T

IS-IS Incremental SPF

Integrated IS-IS can be configured to use an incremental SPF algorithm for calculating the shortest path first routes. Incremental SPF is more efficient than the full SPF algorithm, thereby allowing IS-IS to converge faster on a new routing topology in reaction to a network event.

Reducing Alternate-Path Calculation Times in IS-IS Networks

IS-IS Mechanisms to Exclude Connected IP Prefixes from LSP Advertisements

Beginning with Cisco IOS Release 12.3(2)T, IS-IS caches routes that are redistributed from other routing protocols or from another IS-IS level into a local redistribution cache that is maintained by IS-IS. Caching occurs automatically and requires no configuration. The caching of redistributed routes improves IS-IS convergence time when routes are being redistributed into IS-IS. IS-IS caching of redistributed routes increases the performance of LSP generation, significantly improving network scalability.

Reducing Alternate-Path Calculation Times in IS-IS Networks

IS-IS Support for Route Tags

The IS-IS Support for Route Tags feature provides the capability to tag IS-IS route prefixes and use those tags in a route map to control IS-IS route redistribution or route leaking.

Reducing Alternate-Path Calculation Times in IS-IS Networks

12.2(15)T

Integrated IS-IS Nonstop Forwarding (NSF) Awareness

The Integrated IS-IS Nonstop Forwarding (NSF) Awareness feature allows customer premises equipment (CPE) routers that are NSF-aware to help NSF-capable routers perform nonstop forwarding of packets. This feature is part of the software code and requires no configuration.

Integrated IS-IS Nonstop Forwarding (NSF) Awareness

12.2(13)T

IS-IS HMAC-MD5 Authentication and Enhanced Clear Text Authentication

The IS-IS HMAC-MD5 authentication feature adds an HMAC-MD5 digest to each IS-IS protocol data unit (PDU). The digest allows authentication at the IS-IS routing protocol level, which prevents unauthorized routing message from being injected into the network routing domain. IS-IS clear text (plain text) authentication is enhanced so that passwords are encrypted when the software configuration is displayed and passwords are easier to manage and change.

Enhancing Security in an IS-IS Network

12.2(8)T

Integrated IS-IS Point-to-Point Adjacency over Broadcast Media

When a network consists of only two networking devices connected to broadcast media and uses the integrated IS-IS protocol, it is better for the system to handle the link as a point-to-point link instead of as a broadcast link. This feature introduces a new command to make IS-IS behave as a point-to-point link between the networking devices.

This feature improves the network convergence times of the customer's network because it saves the system from electing a designated router (DR), prevents flooding from using CSNPs for database synchronization, and simplifies shortest path first (SPF) computations.

Reducing Failure Detection Times in IS-IS Networks

Cisco IOS Release 15.0M

15.0(1)M

IS-IS Support for an IS-IS Instance per VRF for IP

The IS-IS Support for an IS-IS Instance per VRF for IP feature provides multiple VPN routing and forwarding (VRF)-aware Intermediate System-to-Intermediate System (IS-IS) instances. The VRF functionality allows Internet service providers (ISPs) to separate routing protocol information and propagate it to the appropriate routing table and network neighbors. Using one router with VRF functionality is more cost-effective than using separate routers to separate and forward the routing information.

IS-IS Support for an IS-IS Instance per VRF for IP

Cisco IOS Release XE 3.1.0SG

Cisco IOS XE 3.1.0SG

Integrated ISIS Point to Point Adjacency over Broadcast Media

When a network consists of only two networking devices connected to broadcast media and uses the integrated IS-IS protocol, it is better for the system to handle the link as a point-to-point link instead of as a broadcast link. This feature introduces a new command to make IS-IS behave as a point-to-point link between the networking devices.

Reducing Failure Detection Times in IS-IS Networks

Cisco IOS XE 3.1.0SG

IS-IS Caching of Redistributed Routes

The IS-IS Caching of Redistributed Routes feature improves IS-IS convergence time when routes are being redistributed into IS-IS. This feature introduces new commands for monitoring and maintaining IS-IS redistributed routes.

Reducing Alternate-Path Calculation Times in IS-IS Networks

Cisco IOS XE 3.1.0SG

IS-IS HMAC-MD5 Authentication

The IS-IS HMAC-MD5 authentication feature adds an HMAC-MD5 digest to each IS-IS protocol data unit (PDU). The digest allows authentication at the IS-IS routing protocol level, which prevents unauthorized routing message from being injected into the network routing domain. IS-IS clear text (plain text) authentication is enhanced so that passwords are encrypted when the software configuration is displayed and passwords are easier to manage and change.

Enhancing Security in an IS-IS Network

Cisco IOS XE 3.1.0SG

IS-IS Incremental SPF

Integrated IS-IS can be configured to use an incremental SPF algorithm for calculating the shortest path first routes. Incremental SPF is more efficient than the full SPF algorithm, thereby allowing IS-IS to converge faster on a new routing topology in reaction to a network event.

Reducing Alternate-Path Calculation Times in IS-IS Networks

Cisco IOS XE 3.1.0SG

IS-IS Limit on Number of Redistributed Routes

The IS-IS Limit on Number of Redistributed Routes feature provides for a user-defined maximum number of prefixes that are allowed to be redistributed into IS-IS from other protocols or other IS-IS processes. Such a limit could help prevent the router from being flooded by too many redistributed routes.

Reducing Alternate-Path Calculation Times in IS-IS Networks

Cisco IOS XE 3.1.0SG

IS-IS Mechanism to Exclude Connected IP Prefixes from LSP Advertisements

Beginning with Cisco IOS Release 12.0(22)S, IS-IS caches routes that are redistributed from other routing protocols or from another IS-IS level into a local redistribution cache that is maintained by IS-IS. Caching occurs automatically and requires no configuration. The caching of redistributed routes improves IS-IS convergence time when routes are being redistributed into IS-IS. IS-IS caching of redistributed routes increases the performance of LSP generation, significantly improving network scalability.

Reducing Alternate-Path Calculation Times in IS-IS Networks

Cisco IOS XE 3.1.0SG

IS-IS Limit on Number of Redistributed Routes

The IS-IS Limit on Number of Redistributed Routes feature provides for a user-defined maximum number of prefixes that are allowed to be redistributed into IS-IS from other protocols or other IS-IS processes. Such a limit could help prevent the router from being flooded by too many redistributed routes.

Reducing Alternate-Path Calculation Times in IS-IS Networks

Cisco IOS XE 3.1.0SG

IS-IS Support for IP Route Tags

The IS-IS Support for Route Tags feature provides the capability to tag IS-IS route prefixes and use those tags in a route map to control IS-IS route redistribution or route leaking.

Reducing Alternate-Path Calculation Times in IS-IS Networks

Cisco IOS XE 3.1.0SG

IS-IS Support for Priority-Driven IP Prefix RIB Installation

The IS-IS Support for Priority-Driven IP Prefix RIB Installation feature allows customers to designate a subset of IP prefixes advertised by Integrated IS-IS for faster processing and installation in the global routing table as one way to achieve faster convergence. For example, Voice over IP (VoIP) gateway addresses may need to be processed first to help VoIP traffic get updated faster than other types of packets.

Reducing Alternate-Path Calculation Times in IS-IS Networks