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Orion Reported Discards

Does anyone know what Orion considers a discard? We have been seeing an increased number of discards in our backbone but the links that are showing this problem are no where close to saturation. I haven't found any information in the Solarwinds website that can define what Solarwinds considers a discard or what switch/router counter looks to find this information.

Thanks,
Jose

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Isaac

Hi there Jose,

Orion looks at the standard mib for discards:
1.3.6.1.2.1.2.2.1.13 receive
1.3.6.1.2.1.2.2.1.19 transmit

Are your backbone devices Cisco?

If so there are a number of scenarios in which you will see discards even if a link is not being saturated with traffic. In my experience it is either a cabling issue or an issue with the electronics of the transmitter or receiver for a particular interface. If you are dealing with GIG Ethernet and using GBICs for your backbone links this is even more likely. The discards are caused by a number of improper frame formats (CRC issues, length, corrupted headers, etc...).

As always check the cabling first. After that has been verified check the backbone link interfaces to verify proper operation.

tinmac

I am seeing the same issue on my network. I am using cisco equipment, but not sure it is a cabling or frame format issue. My network runs great for days and then I will get hit with a few thousand discards on one of my backbone switches all at once then everything goes back to normal for a while. This will happen on different backbone switches randomly. Lines are not close to being saturated, we are talking maybe 2% utilization. Anyone have any ideas?

bleearg13

If your network happens to be a Juniper network, there are such things as 'policed discards' which show up at layer 2. These discards are typically something like CDP or FDP or some other layer 2 protocol that Juniper doesn't understand. It's not a problem, just more of an informational thing.

I would imagine that other non-Cisco devices would also see this behavior, as CDP is proprietary to Cisco, although I believe Foundry and HP do interpret CDP.

-eric

MRoberts

I just finished an eval of NetMRI and it also confirmed some routing discards on the network. For each statistic, it displays a definition or basis for the alert.
The description for routing discards is:

" The following routers experienced more than 50 IP routing discards during the day of 2005-03-28. IP routing discards are the number of routing entries which where chosen to be discarded even though they are valid. A possible reason for IP routing discards could be to free buffer space to make room for other routing entries "

Now, you could request SW to provided its description for the stats it displays or a link to a page with such information.

Marlon.A.Roberts
Network Management Systems Engineer.
ITSD/Verizon/SIM&S INC.
Network Control
732-532-5000
Marlon.A.Roberts@us.army.mil
"Learn By Doing"

Network_Guru

Marlon,

Thanks for the info, but I believe the discards seen in Solarwinds are Layer2 related.
The info you have provided appears to be Layer3 IP routing drops/discards as opposed to interface packet drops/discards(switch of router interfaces).

-=Cheers=-
NG

dlehman

quote:Originally posted by janunez

Does anyone know what Orion considers a discard? We have been seeing an increased number of discards in our backbone but the links that are showing this problem are no where close to saturation. I haven't found any information in the Solarwinds website that can define what Solarwinds considers a discard or what switch/router counter looks to find this information.

Thanks,
Jose

The discards can also be caused by packets with an MTU size that is to large and have the DF bit set. I have a Cisco router that is the endpoint of an IPSec tunnel which reduces the MTU size to less than 1500. With servers (both Windows and Linux) doing PMTU discovery, they occasionally send out packets with the DF bit set and the packets are too large to go through the tunnel. The Cisco router reports these as discards.