Another IP SLA scenario for automated failover

Answered Question
Sep 7th, 2010
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Dear All,


I have another scenario as shown below for achieving automated failover on my WAN links.


Here I am having ISP cloud as a primary link and when ever that fails I need to go over ISDN link which acting as a backup.


I am using basic static routes to achieve same where I am changing the AD for failover, but the problem is due to some reason whenever my ISP link fails at one end that end uses ISDN as per requirement but other end continues using ISP so connectivity fails.


As per discussion with ISP probable solution according to them for this issue is use of IP SLA as primary thing and then OSPF, so need to understand how IP SLA can be used in this scenario.


First thing I will create IP sla for ICMP ping, and I will schedule that monitor event, but how do I map it in this scenario.


Please assist, thanking you all in advance.


Regards,

Mangesh.


                                                                 ISP CLOUD

                                                              -----------------------

                                                                  /             \

                                                               /                   \

                                                            /                         \

                                                         /                               \

                                                      /                                     \

                                                   /                                           \   


                                     ROUTER--------------------ISDN-------------------ROUTER

                                          HO                                                     BR

Correct Answer by Lei Tian about 6 years 10 months ago

Hi Mangesh,


It is there. Search 'Static Routing Examples'

ip route 0.0.0.0 0.0.0.0 10.1.1.242 track 123

HTH,
Lei Tian

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Nagaraja Thanthry Tue, 09/07/2010 - 05:18
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  • Cisco Employee,

Hello Mangesh,


You can use the WAN IP as the ICMP target in both ends. That will ensure

that when the WAN IP is unreachable, both ends will switch to ISDN.


Regards,


NT

mangesh.kamble Tue, 09/07/2010 - 12:11
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Dear Lei,


Yes that is what I was actually looking for, I have another query which actually making me bite my nails and that is the command track 123 rtr 1 reachability.


In my other post where we are using HSRP we are calling this track object 123, but here we are not doing anything of that kind.


Can you please elaborate how exactly track command works?


Thanking you.


Regards,

Mangesh.

Lei Tian Tue, 09/07/2010 - 12:33
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  • Cisco Employee,

Hi Mangesh,


The 'track 123 rtr 1 reachability' just associate the object, ip sla monitor instance (1), with that tracking instance (123). You also need to associate that tracking instance with the static route. During normal operation, tracking instance returns a up, and the static route remains in RIB; during failover, tracking instance returns a down, and static route will be removed from RIB.


HTH,

Lei Tian

mangesh.kamble Tue, 09/07/2010 - 12:54
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Exactly, "You also need to associate that tracking instance with the static route. "


But this thing is not done in the doc provided by you, So just was curious how can we map in inside a static route?


Please assist, thaning you in advance.


Regards,

Mangesh.

Correct Answer
Lei Tian Tue, 09/07/2010 - 13:16
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  • Cisco Employee,

Hi Mangesh,


It is there. Search 'Static Routing Examples'

ip route 0.0.0.0 0.0.0.0 10.1.1.242 track 123

HTH,
Lei Tian

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