IP Service Level Agreement (SLA) & Enhanced Object Tracking (EOT)

Cisco routers can dynamically react to changing network conditions using IP SLA and Object Tracking. These features are often used to influence HSRP priorities, static routes, or routing protocol failover.

Basic Object Tracking

Interface State Tracking

This monitors whether an interface is up at Layer 1 (line-protocol) or Layer 3 (IP routing).

track 100 interface GigabitEthernet0/0/0 line-protocol

Use Case: HSRP will decrement priority if the interface goes down.

standby 1 track 100 decrement 10

If this tracked interface goes down, the HSRP group will reduce its priority, which may cause it to lose active status — allowing the standby router to take over.

IP Routing Capability Tracking

This tracks if the interface has a working IP routing path, not just a physical link.

track 101 interface GigabitEthernet0/0/0 ip routing

Use Case: Interface might be physically up, but not routing (e.g., downstream device failure). HSRP can still react based on IP reachability.

Static Route Reachability Tracking

This tracks the presence of a route in the RIB (routing table).

track 110 ip route 10.10.10.0/24 reachability

Use Case: If a static route disappears, HSRP will reduce priority, or a tracked static route will be withdrawn entirely.

IP SLA Integration with Tracking

IP SLA generates synthetic probes (ping, TCP, UDP) to verify real-time availability of a remote destination.

Example: ICMP Echo with Static Route Tracking

ip sla 1
 icmp-echo 8.8.8.8 source-ip 10.100.2.59
 frequency 5
 timeout 6000

ip sla schedule 1 start-time now life forever

Tie to tracking:

track 1 ip sla 1

ip route 0.0.0.0 0.0.0.0 10.100.2.1 track 1

Use Case: If the router cannot reach 8.8.8.8, the static route to 10.100.2.1 is removed — preventing black-hole routing and enabling failover to a backup path.

Example: TCP/UDP Port Availability Between Routers

R2 – Initiator

ip sla 2
 tcp-connect 10.100.1.1 80 source-ip 192.168.1.25 control disable
ip sla schedule 2 start-time now life forever

ip sla 3
 udp-connect 10.100.1.1 80 source-ip 192.168.1.25 control disable
ip sla schedule 3 start-time now life forever

R1 – Responder

ip sla responder tcp-connect ip 10.100.2.1 port 80
ip sla responder udp-echo ip 10.100.2.1 port 80

Use Case: Track port-level availability of a remote server (e.g., web service). If the service fails, you can withdraw routes or reduce HSRP priority.

Enhanced Object Tracking (Track Lists)

Track lists allow evaluating multiple objects together, providing more robust failure logic.

Boolean Tracking (AND, OR, NOT)

track 10 list boolean and
 object 1
 object 2 not
 delay up 10 down 20

Use Case with HSRP:

standby 1 track 10 decrement 20

HSRP priority is reduced only if object 1 is down and object 2 is up. This allows refined failover logic — e.g., only fail if a primary path fails but a backup stays up.

Threshold Tracking – Weight

Objects contribute weighted values. The combined weight is compared against thresholds.

track 20 list threshold weight
 object 1 weight 60
 object 2 weight 40
 threshold weight up 70 down 30
 delay up 5 down 10

Use Case with Static Route:

ip route 0.0.0.0 0.0.0.0 10.100.2.1 track 20

• Route remains up if total object weight is ≥ 70
• Route is withdrawn if total drops below 30

This provides a graded failover strategy — useful when monitoring different link types (e.g., MPLS and Broadband).

Threshold Tracking – Percentage

Objects are equally weighted; the logic uses percentage of how many are up.

track 30 list threshold percentage
 object 1
 object 2
 object 3
 threshold percentage up 100 down 50
 delay up 5 down 5

Use Case with HSRP:

standby 1 track 30 decrement 15

• HSRP priority is reduced if fewer than 50% of monitored services are up
• All must be up to restore full status

HSRP Application – Complete Examples

Interface-Based HSRP Failover

track 100 interface GigabitEthernet1/0/0 ip routing

interface GigabitEthernet0/0/0
 ip address 10.1.0.21 255.255.0.0
 standby 1 preempt
 standby 1 ip 10.1.0.1
 standby 1 priority 110
 standby 1 track 100 decrement 10

Use Case: Fail HSRP over if routing is lost on the upstream interface.

Route-Based HSRP Failover

track 100 ip route 10.2.2.0/24 reachability

interface GigabitEthernet0/0/0
 ip address 10.1.1.21 255.255.255.0
 standby 1 preempt
 standby 1 ip 10.1.1.1
 standby 1 priority 110
 standby 1 track 100 decrement 10

Use Case: Fail HSRP if a remote site route is lost due to upstream failure — even if local interfaces are still up.