- Preface
- Product Overview
- Configuring the Router for the First Time
- Configuring a Supervisor Engine 720
- Configuring a Route Switch Processor 720
- Configuring NSF with SSO Supervisor Engine Redundancy
- ISSU and eFSU on Cisco 7600 Series Routers
- Configuring RPR and RPR+ Supervisor Engine Redundancy
- Configuring Interfaces
- Configuring a Supervisor Engine 32
- Configuring LAN Ports for Layer 2 Switching
- Configuring Flex Links
- Configuring EtherChannels
- Configuring VTP
- Configuring VLANs
- Configuring Private VLANs
- Configuring Cisco IP Phone Support
- Configuring IEEE 802.1Q Tunneling
- Configuring Layer 2 Protocol Tunneling
- Configuring L2TPv3
- Configuring STP and MST
- Configuring Optional STP Features
- Configuring Layer 3 Interfaces
- Configuring GTP-SLB IPV6 Support
- IP Subscriber Awareness over Ethernet
- Configuring UDE and UDLR
- Configuring Multiprotocol Label Switching on the PFC
- Configuring IPv4 Multicast VPN Support
- Configuring Multicast VPN Extranet Support
- Configuring IP Unicast Layer 3 Switching
- Configuring IPv6 Multicast PFC3 and DFC3 Layer 3 Switching
- Configuring IPv4 Multicast Layer 3 Switching
- Configuring MLDv2 Snooping for IPv6 Multicast Traffic
- Configuring IGMP Snooping for IPv4 Multicast Traffic
- Configuring PIM Snooping
- Configuring Network Security
- Understanding Cisco IOS ACL Support
- Configuring VRF aware 6RD Tunnels
- Configuring VLAN ACLs
- Private Hosts (Using PACLs)
- Configuring IPv6 PACL
- IPv6 First-Hop Security Features
- Configuring Online Diagnostics
- Configuring Denial of Service Protection
- Configuring DHCP Snooping
- Configuring Dynamic ARP Inspection
- Configuring Traffic Storm Control
- Unknown Unicast Flood Blocking
- Configuring PFC QoS
- Configuring PFC QoS Statistics Data Export
- Configuring MPLS QoS on the PFC
- Configuring LSM MLDP based MVPN Support
- Configuring IEEE 802.1X Port-Based Authentication
- Configuring IEEE 802.1ad
- Configuring Port Security
- Configuring UDLD
- Configuring NetFlow and NDE
- Configuring Local SPAN, RSPAN, and ERSPAN
- Configuring SNMP IfIndex Persistence
- Power Management and Environmental Monitoring
- Configuring Web Cache Services Using WCCP
- Using the Top N Utility
- Using the Layer 2 Traceroute Utility
- Configuring Bidirectional Forwarding and Detection over Switched Virtual Interface
- Configuring Call Home
- Configuring IPv6 Policy Based Routing
- Using the Mini Protocol Analyzer
- Configuring Resilient Ethernet Protocol
- Configuring Synchronous Ethernet
- Configuring Link State Tracking
- Configuring BGP PIC Edge and Core for IP and MPLS
- Configuring VRF aware IPv6 tunnels over IPv4 transport
- ISIS IPv4 Loop Free Alternate Fast Reroute (LFA FRR)
- Multicast Service Reflection
- Y.1731 Performance Monitoring
- Online Diagnostic Tests
- Acronyms
- Cisco IOS Release 15S Software Images
- Index
Configuring Link State Tracking
This chapter describes how to configure the Link State Tracking in Cisco IOS Software Release 15.1(01)S.

Note For complete syntax and usage information for the commands used in this chapter, see the Cisco 7600 Series Router Cisco IOS Command Reference at this URL: http://www.cisco.com/en/US/products/ps6922/prod_command_reference_list.html
Understanding How Link State Tracking Works
When a link failure occurs on a REP and MST segment, the associated protocols handle the link failure event. However, if the primary link to the switch is enabled even though the corresponding uplink ports on the switch are disabled, the REP and MST protocol is unaware of backbone side, and does not trigger a failover. The router continues to receive the traffic from the access side and then drops it discreetly due to lack of backbone connectivity. Link state tracking provides a solution to this problem by allowing the uplink interfaces to bind the link status to the down link ports. Uplink state tracking is configured such that when a set of uplink ports are disabled, other ports linked through CLI commands are disabled as well. The state of all the downlink interfaces are error-disabled only when all the upstream interfaces are disabled.
The LST triggers REP/MST re-convergence on the access side depending on the state of the core-facing interface. The link state of the core facing interface and the access facing interface are bound by link state tracking group.
– Enabling and disabling of link state group tracking.
– Removal of downstream interfaces from a link state group.
– Performing shut/no shut on error disabled interface.
Restrictions and Usage Guidelines
Follow these restrictions and usage guidelines when you configure the LST:
- Ensure that the management interfaces are not part of a link state group.
- REP port cannot be configured as uplink port.
- LST does not allow any interface, upstream or downstream, to be part of more than one link state group.
- You can configure a maximum of 10 link state groups.
- When you configure LST for the first time, you must add upstream interfaces to the link state group before adding downstream, otherwise the state of the downlink interfaces are error-disabled.
- The configurable interfaces are physical (both routed and switch port), port-channel, sub-interface and VLAN.
- Upstream interfaces are required to be among:
Configuring Link State Tracking
Perform the following tasks to configure a Link State Tracking:
This example shows how to create a link-state group and configure the interfaces:
The show link state group command displays the link-state group information.
The show link state group detail command displays detailed information about the group.
(Up):Interface up (Dwn):Interface Down (Dis):Interface disabled
Troubleshooting the Link State Tracking
Table 69-1 lists the troubleshooting issues while configuring LST:
Table 69-1 Troubleshooting LST Issues