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Configuring and using IP SLA

Here comes a brief guide on how to implement and use IP SLA.

IP SLA parameters

Timeout: time to wait for response before classifying as down.

Threshold: time to trigger an event. You can for example set a threshold value for which you send a notification event with SNMP that a threshold RTT is reached.

Frequency: How often IP SLA is run.

Configure IP SLA

1. Defining the IP SLA:

Ip sla 100
Icmp-echo 8.8.8.8 source-interface gi0/0
Threshold 2000
Timeoute 5000
Frequency 5

2. Scheduling the IP SLA.

ip sla schedule 100 life [forever|seconds]  start-time [now|time]

3. Creating a tracker to use in ip route, hsrp track etc:
Track 1 ip sla 100 state

So config example summarization:

Ip sla 100
Icmp-echo 8.8.8.8 source-interface gi0/0
Threshold 2000
Timeout 5000
Frequency 5
Ip sla schedule 100 life forever start-time now
Track 1 ip sla 100 state

This creates an IP SLA that pings google dns every 5 seconds, it has a threshold with 2seconds and a timeout of 5s. It is scheduled to start immediately and runs forever until the schedule command is negated. “Track 1” is used to refer to the IP SLA in other configurations.

Example:

Interface  gi1/0
Standby 1 address 192.168.1.1
standby 1 track 1 decrement 100

—-or—–

Ip route 192.168.2.0 255.255.255.0 192.168.1.1 track 1

The example with hsrp config tracks the ip sla, and if the tracked address stops responding to ping, the hsrp priority is decremented by 100. The ip route is also tracking the same IP SLA, causing the route to be revoked if the host stops responding to ping according to the sla configuration.

One Reply to “Configuring and using IP SLA”

  1. Everyone loves it when people come together
    and share thoughts. Great site, continue the good work!

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