Per VLAN Stats on MSFC2 - Complaints from the Field
narziss at cdardn.net
Thu Nov 20 17:52:02 UTC 2003
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
can be circumvented by disabling MLS on your fabric, but will result in
all of your packets being process switched, inherently increasing the
CPU load of your MSFC/CPU.
Depending on your configuration, your SVI information can be coupled
with the Layer 2 SNMP statistics (at least for I/O) to provide more
I apologize if I have missed something, but I'm assuming this is what
you're alluding to.
Robert A. Hayden wrote:
> Hey all,
> This one is a weird one. I apologize if this is a bit off topic.
> As everyone is probably aware, the Cisco 6500/7600 line is unable to
> provide per-vlan I/O statistics on routed interfaces (ie, a "show int vlan
> xxx" has meaningless numbers in the I/O and error fields at the end).
> MIB tables also fail to provide meaningful data. You CAN get some L2 VLAN
> data, but that doesn't help you when you need to know what's going through
> the router interface.
> We've be going around and around with the vendor for a while now about how
> this makes it pretty useless for traffic analysis, and even showed them
> the RFC that requires that the information be made available to call it a
> router. Their latest tactic is to claim that "nobody else in the industry
> is concerned about this shortcoming".
> For us, we've been collecting routed interface stats going back all the
> way to 1996 and with our new gear we've been sold we find that our graphs
> are pretty empty and we get no reasonable information about how much
> traffic is passing through the L3 interfaces.
> So, here's the question I have for anybody out there dealing with this
> hardware. Is this shortcoming an issue for how you run your network?
> Have you asked Cisco to fix it? My feeling is that a lot of people find
> it to be an issue and simply accept it is yet another broken cisco thing.
> Please let me know privately. I want to talk into our next meeting with
> some printed testimonials from "real people" that this box is plain
> broken. Let me know as well if you don't want me to use your name and/or
> organization in my report.
> Thanks for your time.
> - Robert Hayden
> University of Wisconsin Madison
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