Re: Cisco Juniper MRTG Different Result

cwy · ‎06-16-2008

Hi all,

I have a connection connected a Cisco router and a Juniper Router. After I setup a MRTG server to monitor the interfaces of both routers. I found the MRTG show the traffic utilization is different. The utilization of Cisco seems higher than the Juniper. Also I show the interface counter of both routers to verify, and the result also the same.

Any one faced this before? And any idea about this?

THX.

Andy

dave.keith · ‎06-18-2008

I recall a study done by Edwin Mier many moons ago where he compared SNMP counters on various products. The bottom line was that few were even close to 100% accurate. Some were way off. I can't comment on the accuracy of the counters in your specific products, but as long as they show similar numbers I wouldn't worry about them not being exactly the same. I see different SNMP counter numbers (ifInNUcastPkts) from interconnected IOS and CatOS interfaces.

Dave

andrew.burns · ‎06-19-2008

Hi,

When you say "different", just how different are they? Can you quantify it for us.

Andrew.

cwy · ‎06-22-2008

Hi Andrew,

Thanks for your reply. According to the MRTG graph, there is around 20% different between Cisco and Juniper interfaces.

THX!

Andy

andrew.burns · ‎06-22-2008

Hi,

I can think of a couple of reasons why they might be a little different, but nothing that would explain that much of a difference.

Are you polling them using the same interval? Or maybe one end is sending something that the other end isn't receiving?

Is the difference equally spilt between unicast/broadcast/multicast?

Andrew.

cwy · ‎06-23-2008

Hi Andrew,

The interval are the same. I didn't anaylse the traffic, but the sending and receiving of both ends should be the same.

The unicast should equally split. And there is no multicast. Also the broadcast traffic should not cause sure big difference, I think.

THX!

Andy

andrew.burns · ‎06-23-2008

Hi,

Can you post the show interface output from both devices, for two time periods? I.e. show interface at the same time, wait a while (a reasonably long time such as an hour or so) then collect show interface from both devices again?

Andrew.