Strange with two cisco routers

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Feb 15th, 2010
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I have a cisco 2821 connected to a server with ip and all traffic goes to this router.This server only uses this router.  There is another cisco 1841 router with ip and all servers use this device.

When I open a terminal session in the first server(router ip  and ping for example or some packets go frm server to and then to and or amazon.....not always happends but sometimes.


The server has as default route not 254.

Best regards

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Federico Coto F... Mon, 02/15/2010 - 11:56
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Are both routers (2821 and 1841) connected to the same switch?

I see they both are on the same subnet.

Could be a configuration issue on the switch.

Could you attach that configuration as well?


Federico Coto F... Mon, 02/15/2010 - 12:13
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I am responding in english so that everybody understands...

This could be a normal behavior, for example if for a moment the 2821 could not reach its internet access, it has another way to reach the Internet, through the 1841...

Could you share with us a snapshot of the topology?


edgar.quintana Mon, 02/15/2010 - 12:40
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There are, for this topic, two swtiches.

1st for lan 192.168.157.x

2nd for x.x.x.81 and internet.

Both router have one interface connected to lan and 2nd to this swtich.

Federico Coto F... Mon, 02/15/2010 - 12:45
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Like I said,

Could be that the connection from the 2821 to the Internet is interrumpted, and therefore it get's out through the other router (being both on the same subnet).

Can you test that when this happens, there's a lost in the connection from the 2821 to the Internet? I think this is what's happening...

Is this affecting the network in anyway?


Giuseppe Larosa Mon, 02/15/2010 - 14:47
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Hello Federico,

the two routers have both

no ip proxy-arp on internal LAN interfaces or external interfaces

there is  no backup floating static route pointing to the other router or a dynamic routing protocol.

even if router1's wan interface fails it should not be able to detect the other router is still able to reach the internet.

So I agree it is strange

Are the two routers connected to the same IP subnet also on the ip nat outside ?

Hope to help



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