change the WAN link when bandwidth is too low

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Mar 28th, 2008
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I have a router with 2 ethernet and 2 serial interfaces.I want to change my WAN link dynamically when the bandwidth is too low(the traffic will exit the LAN through the other serial interface).


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Goutam Sanyal Fri, 03/28/2008 - 00:30
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Roland, Can you post more details about your network infrastructures? Like is the WAN is connected with Serial only or you are also using the same as well as Merto Ethr also? Thanks Goutam

roland_costea Fri, 03/28/2008 - 00:43
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I have 2 serial connections with 2 different ISPs but I'm using only one for all my LAN traffic...I want to change the link and use the second ISP when the bandwidth supplied by the first is too low

Goutam Sanyal Fri, 03/28/2008 - 00:57
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Roland, It's also not sufficient for address you perfectly. With your post I can suggest you use when you are using the 2 ISPs Link, the take the full facilities and use the both simultaneously with a load balance facility for your LAN traffic by GLPB. Thanks Goutam [Pls rate if I am informative]

Joseph W. Doherty Fri, 03/28/2008 - 04:56
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Like Goutam, I too would recommend using both your ISP links all the time. How to do this depends on your current configuration. If, for instance, you have a single static default route, you might only need to add another static default route.


ip route x.x.x.x


ip route x.x.x.x

ip route y.y.y.y

roland_costea Fri, 03/28/2008 - 05:43
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that was my question...i know i can do load balancing but i don't want to.I want to manage the bandwidth parameter only(if iti is lower than x then switch link) and I'm curious if i can do that.Thank you for your answers.I can't use glbp because i have only one router!

roland_costea Fri, 03/28/2008 - 05:48
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and if i'm using 2 default routes with different metrics i supposed the single case when the second route will be in the routing table is when the first goes down...and that's not what i want...i want to switch links only if the first one i'm using will have a bandwidth lower than a specific value...not if it will go down!

Joseph W. Doherty Fri, 03/28/2008 - 05:57
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No, I wasn't thinking of first link going doing, I was thinking of equal metrics. I.e. both links would be hot all the time.

However, if you really only want to switch or add bandwidth based on load, Narayan's suggestion of EEM might allow you to monitor the load on the primary link, and change your config dynamically. You could either make the second path primary or make it equal cost.


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