[c-nsp] snmp counters wrong for SVI with multicast

[Tony]

Hi,

I recently had similar problems and logged a case with TAC. After discussing/arguing with them for quite some time (2 cases over a period of 4-5 months) they were finally able to reproduce my issue and the net result was:

Filed a bug
: CSCtj63596 &
the fix is available in 12.2(33)SRE3
I don't know if this is the same problem as you, but the symptoms are similar (the bug description is fairly vague). I was getting twice the real bandwidth usage in certain monitoring intervals, not continually though. It didn't seem to be specific to multicast in my case, but the box in question does have other multicast traffic through it.

We are currently running 12.2(33)SDR4 and I haven't yet had a chance to upgrade to the version indicated above so I can't tell you whether it has fixed the problem as TAC suggests.


If you do upgrade, it would be good to know if it fixes your issue (as it could be related to similar code about SNMP stats).


regards,
Tony Miles.




________________________________
 From: Artyom Viklenko <artem at aws-net.org.ua>
To: "cisco-nsp at puck.nether.net" <cisco-nsp at puck.nether.net> 
Sent: Wednesday, 4 April 2012 5:33 PM
Subject: [c-nsp] snmp counters wrong for SVI with multicast
 
Hi, List!

Apparently I found some strange situation. We use Cacti to
draw interfaces utilization on our 7600 routers w/RSP720-3CXL-GE.
The problem is that cacti draws more traffic on vlan interface
that it is really forwards and this is only in cases when
multicast traffic inbound or outbound is present. More over
if some interface vlan used for only multicast delivery
(iptv in our case) cacti showes bandwidth near two times more
than it actually forwards. If some interface vlan receives
multicast and unicast - cacti also draws more input. and
delta typically equals to total multicast stream bandwidth.

I try to draw some graphs using anoter host and anoter software
MRTG. And it also reveals this problem. F.e. I have physical
port say Gi2/1 configured as trunk and only one vlan say 333.
if I grapth Gi2/1 - it showes 280Mbps input. At the same time
graph for vlan333 showes 400Mbps input!

'show interface xxx' displays relatively equal load on both
interfaces.

IOS is 12.2(33)SRD6 ADVIPSERVICES. Try to search release notes
and didn't found any relevant.

Does anybody know what is this and how to fix it.
I'm preparing to upgrade to SRD7 but still dont know is this
fix the problem. And in release notes still nothing about this.

Thanks in advance!

--            Sincerely yours,
                            Artyom Viklenko.