Failover between-FE-Serial link-Using Ospf

Unanswered Question
Aug 26th, 2009

Hi All,


We are going to add an ethernet point to point Wifi link between our HO-Branch office.right now we have a serial leased line 512kB link between these two location. we are running OSPF as routing protocol.now my concern is regarding the cost value since fastethernet link has cost 1 the ethernet link will prefer to route the traffic.( we actually plan to keep primary as Wifi-ethernet link)


Since ethernet interface never go down(always show up) when the connectivity loses to the other end will the traffic switch over to serial leased line?



If no any method to make it switch over.


Thanks in advance

Shibu

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Jon Marshall Thu, 08/27/2009 - 01:38

Shibu


Is the wifi link running off a different router than the serial link ?


Could you clarify the router setup.


You can use ip sla to track the availability of the next-hop and if that next-hop is not pingable then you can switch to another route. Depending on your router setup you could use HSRP track or you may need to use a slightly different method.


Jon

Shibu1978 Thu, 08/27/2009 - 01:44

Hi Jon,


Thanks for your reply.


No...both links are in the same router at both end. one end we have 3825 and other end we have 7206 router.



Joseph W. Doherty Thu, 08/27/2009 - 03:21

BTW, regarding the OSPF cost value, you can override it either providing an explicit OSPF cost for the interface, or, since I suspect the WiFi connection provides much less than FE bandwidth, change the bandwidth to reflect what's actually available across that link.


Since you have routers at both ends of the the WiFi link, and if they form as OSPF neighbors, if they can't pass traffic but the local interface remains up, OSPF will lose connectivity to its neighbor router across the path and OSPF should stop using it. ([edit] i.e. traffic should then use the slower link and switch back to the faster link when and if the routers can communicate across it.)

Shibu1978 Thu, 08/27/2009 - 03:49

Thanks!!!


So i hope i dont need to use IP sla feature for this type of connection. i can manipulate cost value or bandwidth for selecting the links.


Thanks for the great input



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