How to turn SLA on and off

[dschlic1]

We have a Cisco switch which has a SLA commands and tracking objects to turn on and off a route. This is used to fail over from one route to another to provide path redundancy. The issue we are having, which seems insolvable, is that the pings generated by the SLA are being routed by the current active routes. So one option that I have thought of is if it is possible to turn a SLA and/or tracking object on and off via say SNMP, this might solve the issue we are currently facing. Is it possible to do this?

[balaji.bandi]

You also reach destination for IP SLA using source interface, not required to active route.

Other part not sure if i understand question correctly please give us more information.

[dschlic1]

The firmware level on our 370 switch does not accept source-interface in the SLA command. The system has two paths: one cellular and one via radio. The cellular path is setup to be the primary ad the radio the secondary. We are currently using the following for each redundant station:

ip sla 10

icmp-echo 10.16.2.10 source-ip 10.18.252.1

ip sla schedule 10 life forever start-time now

track 10 ip sla 10 reachability

ip route 10.16.2.10 255.255.255.255 10.18.252.2 track 10

ip route 10.16.2.10 255.255.255.255 10.15.2.10 201

The 10.16.2.10 is the cellular address which is used for all communications. 10.15.2.10 is the radio side IP address. 10.18.252.1 is the router port address that is connected to the cellular system. 10.18.252.2 is the IP address of the cellular provider's interface. What is happening is when the cellular path goes down the first ip route is disabled by the tracking object, leaving the second ip route which directs all traffic via the radio side. Unfortunately what also occurs is the pings for the SLA are also directed out the radio side by the second ip route statement. We have not found a way to prevent that.

If both sides are down (say the station is powered down) the 3750 switch does not receive a ping response so disables the first ip route. Then when the stations comes back up, but for some reason the radio does not, but the cellular side does, then the system deadlocks and will never change back to the cellular side because it will never receive a ping response back via the down but active (from the switch's point of view) radio channel.

[dinns]

Hi dschlic1,

in your ip route statement, can you put the exit interface before the next hop address?  

Unfortunately what also occurs is the pings for the SLA are also directed out the radio side by the second ip route statement. We have not found a way to prevent that.

The primary link (cellular) is already down, so static route via radio will be used.

Regarding your "deadlock" scenario, can you provide more details what device is this (10.16.2.10)? If Radio is up but primary link cellular is down, traffic should route via the former. We would like to see more especially on other side  of the link, perhaps they have a default route pointing back to you only via via cellular, thats why traffic is not using backup link.