Netflow and OTV

[Kevin Dorrell]

Nexus 7700 version 6.2.

Can someone confirm whether this is possible? - I have OTV between two data centres, and I would like to see some statistics concerning which pairs of IP addresses are using the OTV.  The objective is to try and put the pairs of heavy talkers in the same data centre, in order to minimise the traffic across the Data Centre Interconnect.

I tried Netflow on the interfaces of the DCI links.  Yes, I do see the routed flows where the VLANs are specific to each Data Centre.  But for the traffic that goes through the OTV tunnel, I see only the four flows between the OTV join interfaces.  And of course, that amounts to over 99% of the traffic, and so is not very useful.  What I would really like would be to see the individual flows inside the OTV tunnel.

I thought of using layer-2 netflow on the point where the Data Centre joins the OTV vdc, but that only tells me about the MAC addresses ... and of course most of the traffic is to or from a MAC address of one or other of my aggregation routers.

Any ideas anyone?

[Kevin Dorrell]

Anyone?

[mgreylingbcx]

Hi Kevin,

Was looking for the same thing, did you manage to get a workaround?

Have you tried L2 Netflow on the Port-Channel connecting up from your LAN VDC to the OTV VDC? At least then you will be able to look at your ARP table and see which MAC maps to which IP, thus giving you more visibility.

Not ideal, the problems we have to deal with when things gets encapsulated I guess.

[Kevin Dorrell]

Hi,

Thank you for the suggestion.  I did try L2 netfow.  That would let me see the server pairs where they are in the same VLAN, albeit with the inconvenience of having to look up the correspondence in the ARP table.  Unfortunately it is not so useful where the servers are on different VLANs because the source MAC address will always be the aggregation router on the site where the packet is sourced.  That is, server A on site X will go to the aggregation router on site X, which will then switch the packet to server B's VLAN and pass it over the OTV with the source MAC address of the site X router.

Thanks for the suggestion anyway ... I was beginning to think nobody was listening!