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Re: [nsp] Re: Per VLAN Stats on MSFC2 - Complaints from the Field

  • From: Anthony Cennami
  • Date: Thu Nov 20 18:16:25 2003

If you want to bill accurately, bill off the Layer 2 ports; that's what is always churning the traffic. I've not looked at the accuracy on a scientific level, but I've never found what I believed to be a serious discrepency when billing/polling the physical ports.

The reporting of the Layer 2 and 3 devices, virtual or otherwise appears to be correct; I argue that Cisco attempting to 'populate' the SVI counters with information they are actually not seeing would be 'breaking' the implementation. Remember folks, we're talking about multi layer switching/routing here; the SVI isn't processing all of the traffic and should not lie and say that it is.


Hudson Delbert J Contr 61 CS/SCBN wrote:

cisco long ago made the decision that counting packets was NOT as important
processing them. i've seen this thread in discussions about IOS since
Version
9. they arent going to change the methodology right now because we need to
bill off of it. why use the overhead involved with passing info about L2 to L3 if 'train is still moving the cattle'. who cares?


~v/r
Del Hudson
61CS/SCBN - LAAFB NCC
Network Architecture & Engineering Group
[email protected]



-----Original Message-----
From: Gert Doering [mailto:[email protected]]
Sent: Thursday, November 20, 2003 1:43 PM
To: Anthony Cennami
Cc: Nanog Mailing list; Robert A. Hayden; [email protected]
Subject: Re: [nsp] Re: Per VLAN Stats on MSFC2 - Complaints from the
Field


Hi,

On Thu, Nov 20, 2003 at 12:52:02PM -0500, Anthony Cennami wrote:

This is because in 1996 you were likely not dealing with 'Switch Routers'; today's 'routers' perform some form of flow switching/caching, meaning once the traffic enters the VLAN routed interface and an appropriate path is found it is sent down the the Layer 2 fabric. 
This is all nice and shiny, but having shortcuts doesn't mean "the L2
fabric can't export the resulting numbers up to the L3 brain".

They just botched it.  Counters and Cisco boxes seem to be fundamentally
incompatible.

gert