Simone,
I think that you are correct with your assumption that you are only seeing
extended_data relating to layer 2.
The extended_data fields that are exported represent the data that the
device used when it decided how to forward the sampled packet.
This means that a switch operating at layer 2 will be able to export layer 2
information (eg source/destination 802.1p/Q) While a switch that is
forwarding at layer 3 will be able to export layer 3 forwarding information
(eg next hop subnet, source/destination address prefix mask).
The BGP fields can be populated if the device is a BGP router and the
sampled traffic is routed via BGP.
Similarly if the device is web switch and maintains a connection table
mapping to urls, then it is possible for the url to be exported with the
sampled packet.
If you upgrade your switch to run layer 3 software, you should be able to
see the layer 3 extended data for the packets that are forwarded at layer 3.
I hope this makes sense. Please let us know if you would like more
explanation.
Sonia
> Sonia,
>
> I've studied the source code of sflowtool, and I've seen a
> lot of useful information that can be sampled even with sFlow
> v2. As I am running sFlow on a switch (thus, a layer 2
> device), however, the only value that I get for
> extended_data_tag is 1, and the only "extended" information
> that I get regard vlans.
> My questions are the following:
> - looking at the code it seems to me that there is no way (on
> a layer 2
> device) to obtain other extended information, such as BGP or
> URLs, but it would be very useful if you could confirm this.
> - our device has also layer 3 capabilities (but now it is
> running layer
> 2 software): if we upgrade it, could we get other extended
> information?
>
> Thanks in advance.
> Best regards, Simone.
Received on Mon Oct 18 16:22:30 2004
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