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<div class="moz-cite-prefix">On 3/20/23 09:43, Mike Hammett wrote:<br>
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<blockquote type="cite"
cite="mid:2103687210.393.1679326975070.JavaMail.mhammett@Thunderfuck2">
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<div style="font-family: arial,helvetica,sans-serif; font-size:
10pt; color: #000000">But then I'm storing and processing twice
as much data as I need.<br>
<br>
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<br>
<br>
I would say somewhere between 0 - 100% overhead. Depending upon
traffic. <br>
<br>
Recall that a flow is packet delivery in one direction only. An end
to end flow is an ingress interface with various l2 decorations
along with an egress interface with its various l2 decorations
(which many flavours of sflow will report). So you need to record
flows in both directions - from point of entry to point of exit. In
Cisco when I have the ability to turn on ingress and/or egress. I
turn on both so I can record this detail.<br>
<br>
To fully record traffic, you need this in both directions. And
recall, multihome means that traffic delivery may be asymmetrical
across interfaces. So diagnostics will require this full flow info
in both directions.<br>
<br>
And as the disparaged marketing material indicating that a 1G
interface carries 2G worth of traffic, it isn't a lie.<br>
<br>
All this to say that no, you aren't processing twice as much data as
you need. You need all that, in both directions, to properly
generate additional detail reports.<br>
<br>
<blockquote type="cite"
cite="mid:2103687210.393.1679326975070.JavaMail.mhammett@Thunderfuck2">
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<div
style="color:#000;font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt;"><b>From:
</b>"Raymond Burkholder" <a class="moz-txt-link-rfc2396E" href="mailto:ray@oneunified.net"><ray@oneunified.net></a><br>
<b>To: </b><a class="moz-txt-link-abbreviated" href="mailto:nanog@nanog.org">nanog@nanog.org</a><br>
<b>Sent: </b>Monday, March 20, 2023 10:16:37 AM<br>
<b>Subject: </b>Re: Cisco Nexus Odd sFlow Implementation<br>
<br>
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<div class="moz-cite-prefix">On 3/20/23 08:55, Mike Hammett
wrote:<br>
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<blockquote
cite="mid:1373333037.350.1679324104776.JavaMail.mhammett@Thunderfuck2">
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<div style="font-family: arial,helvetica,sans-serif;
font-size: 10pt; color: #000000">Cisco is sending the in
and out packets in their sFlow implementation on their
Nexus switches. Obviously, this double counts the
information.
<div><br>
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<div>Are there solutions that process those flows and
remove one of those directions?<br>
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<br>
Wouldn't you just do that in your reporting? The report
engine usually has options for interface, ingress/egress,
prefix range, protocol, ....<br>
<br>
Then when you need to aggregate for a specific interface for
additional troubleshooting, you have all the information for
when you need it.<br>
<br>
Yes, your aggregate numbers for total packets transiting is
double, but I generally have specific reports for specific
traffic patterns I focus on anyway.<br>
<br>
Raymond Burkholder<br>
One Unified Net Limited<br>
<br>
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