ethernet or fastethernet vs. Serial interface

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Nov 26th, 2009
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Hello friends,

can you please tell me that why we require need to track only to ethernet or fast ethernet interfaces and no need to track serial interfaces?

when the link goes down, ethernet/fast showing ports status as up up and when serial interfaces goes down, interfaces showing as up down, why is so that?

Thanks and Regards,


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Reza Sharifi Thu, 11/26/2009 - 20:33
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When you say track, do you mean VRRP tracking or is this some thing else you are talking about?


sourabh1000_2 Thu, 11/26/2009 - 23:39
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Dear Reza,

please forget about main query is why fastethernet/ethernet interfaces showing UP and UP status only when link gone down and why serial interfaces showing UP and DOWN when link gone down?

Thanks and Regards,


Richard Burts Mon, 11/30/2009 - 10:09
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One part of the explanation of the different behavior between Ethernet/FastEthernet and serial interfaces is that the serial interfaces use a keepalive mechanism that sends keepalive packets over the serial interface and must receive keepalive packets over the serial interface. If the correct keepalives are not received then the serial interface shows up and down. The keepalive on the Ethernet/FastEthernet does not work quite the same way and so the behavior is different.

Another part of the explanation is that while the serial keepalive works end to end over the link the Ethernet/FastEthernet does not check end to end (from router to router or whatever is connected on the Ethernet). The Ethernet/FastEthernet only checks to the next connected device which is usually a switch. So your router Ethernet/FastEthernet will report up and up because it is connected to a switch which is working and does not detect that the router on the other end of the link is down.




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