Difference between IP SLA and HSRP

[mainodin87]

Hey Guys,

Why to use HSRP (where to use exactly) if IP SLA does the same thing. Just want to know the exact reason behind using HSRP.

Regards,

Mainodin

[paul driver]

Hello

IP SLA and HRSP are not the same feature

IP SLA is for traffic montiring
HRSP  is used to provide routing redundency

Please review these documents it will explain far better than I ever can.

Ip sla
Hrsp

res

Paul

[mainodin87]

Dear Paul,

Thanks for the link, but I've already went through it, but am not getting the concept behind these, when is IP SLA used or why it is used if there is HSRP already running ? coz HSRP does monitor the link and provide redundancy for same.

i know am asking very silly question, its just coz am very much confused.

Regards,

Mainodin 

[Jon Marshall]

HSRP is an FHRP (First Hop Redundancy Protocol) used for end devices, clients or servers for example to provide a redundant gateway.

So you would have a pair of L3 devices running HSRP and they share a virtual IP (VIP). One of the switches "owns" the virtual IP and all clients in the vlan send traffic to that switch if they want to send traffic to a remote subnet.

If that switch fails then the other switch takes over the VIP and clients are unaware of the change ie. they just keep on sending traffic to the VIP.

IP SLA is not providing redundancy for end devices.

It is used by L3 devices to track the state of links (and other things). A common usage is where you have a L3 device with a primary and secondary link and you are using static routes.

Because you are using static routes if there is a failure somewhere along the primary path your L3 device may not be aware of and so does not use the static via the secondary link. So with IP SLA you can ping an IP along the path and if the ping fails your L3 device knows there is a problem and can then switch over to the secondary link.

They are two different things and are used for different purposes.

Jon

[mainodin87]

Hey Jon,

Thanks for the input, most of the doubt is clear now, just one more thing, you told

"if the ping fails your L3 device knows there is a problem and can then switch over to the secondary link." with IPSLA

how this happens ? we have to do this manually or some track command has to be used.

Regards,

Mainodin

[Jon Marshall · Accepted solution]

It is done automatically and you track the route with IP SLA.

There are a few different ways to do it the commonest being to track the primary route and then have the secondary route with a higher AD which will only be if the primary path is unavailable.

Jon

[mainodin87]

Hey Jon,

Thank you so much for your clear inputs on my silly confusions :p

GOD Bless

Mainodin