Should REPEATER MIB (RFC1516) and RMON MIB (RFC1757) give the same results?

Should REPEATER MIB (RFC1516) and RMON MIB (RFC1757) give the same results?

Post by Thomas Dzubi » Sat, 03 Oct 1998 04:00:00



I've been happily using the Repeater MIB (RFC2108) to do traffic
statistics
for repeaters and switches on my network, but I've recently received
some
devices which don't "do" RFC2108, so I have to query the RMON MIB
(RFC1757)
for the ports in the device.
(I haven't been using RMON all along because some of my really old
devices
don't support RMON, but they do support the Repeater MIB)

In my devices that support both MIBs, though, I've had some strange
results...

I get substantially different count results from
  RFC2108 rptrMonitorPortReadableOctets = 1128824064
  RFC1757 etherStatsOctets              = 2097785344

(similar results for rptrMonitorPortReadableFrames vs. etherStatsPkts
too)

Any ideas on why they might be sooooooo different?
(It's a 3Com SuperStack II Switch 1000 - it isn't technically a repeater
...maybe I shouldn't even be using RFC2108 against it?? ...perhaps the
bridge MIB (RFC1493)?)

------------
Thomas Dzubin
Network Analyst
Saskatoon, Vancouver, and Calgary CANADA

 
 
 

Should REPEATER MIB (RFC1516) and RMON MIB (RFC1757) give the same results?

Post by Charlie Dellacon » Sat, 03 Oct 1998 04:00:00


Just a guess...  In many RMON devices etherStatsOctets is the sum of both
received and transmitted octets.  Same for the packet count.  RFC1757 says
etherStatsOctets should just be octets received but that was intended for
probe devices not for switches and routers.  Check etherStatsOctets against
(ifInOctets + ifOutOctets) to see if this is the case.  Its looks possible
here since RMON is about double RFC2108 which would suggest a near symmetric
traffic flow if this is the case.

Charlie Dellacona


> I've been happily using the Repeater MIB (RFC2108) to do traffic
> statistics
> for repeaters and switches on my network, but I've recently received
> some
> devices which don't "do" RFC2108, so I have to query the RMON MIB
> (RFC1757)
> for the ports in the device.
> (I haven't been using RMON all along because some of my really old
> devices
> don't support RMON, but they do support the Repeater MIB)

> In my devices that support both MIBs, though, I've had some strange
> results...

> I get substantially different count results from
>   RFC2108 rptrMonitorPortReadableOctets = 1128824064
>   RFC1757 etherStatsOctets              = 2097785344

> (similar results for rptrMonitorPortReadableFrames vs. etherStatsPkts
> too)

> Any ideas on why they might be sooooooo different?
> (It's a 3Com SuperStack II Switch 1000 - it isn't technically a repeater
> ...maybe I shouldn't even be using RFC2108 against it?? ...perhaps the
> bridge MIB (RFC1493)?)

> ------------
> Thomas Dzubin
> Network Analyst
> Saskatoon, Vancouver, and Calgary CANADA