Router Flows

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Oct 14th, 2009
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I'm just needing to find out if I need to setup Netflow on a router or not.


What happens to the VLAN ID info when an IP Packet leaves a router that does not have Netflow enabled. Is it discarded.




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Lucien Avramov Wed, 10/14/2009 - 13:40
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No it is not discarded at all.

The netflow header is optionnal and doesnt impact traffic.


You dont need netflow to have proper data traffic.

infosateng Wed, 10/14/2009 - 13:59
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Ok, so you are saying that when an IP packet leaves the router it keeps its source IP and VLAN information.

Lucien Avramov Wed, 10/14/2009 - 14:05
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I dont understand your question.

Perhaps you have confusion about what netflow is.


Netflow adds extra information in a header with sysuptime and packet flow number. You can read the RFC of netflow for further reference.


Netflow is an optionnal feature for statistics on your network, that can be collected by a Netflow Collector.


You do not need netflow for your router to work, neither netflow to be able to get packets that already have a netflow header on them.



infosateng Wed, 10/14/2009 - 14:20
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Sorry for confusion.


We have some sites which have the same subnet behind their router, but are on different VLANs. I need to find if the IP Packet has both the Source IP and the VLAN ID when it reaches its destination.


I was told the only way to capture this was to use Netflow, but if this information is already there, obviously I don't need to enable Netflow.


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