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5500G-EL discards on cascade ports

Occasional Contributor

5500G-EL discards on cascade ports

We have two 5500 switches stacked with cascade links at the rear. Two of these links between the two switches show a high number of "discards" when using Solar Winds network monitoring software. Is this a problem? The cpu's of these switches are showing as less than 40% busy

Occasional Collector

Re: 5500G-EL discards on cascade ports

on my ports that I intentionally have stp blocking (or rrpp blocking) the discards are super high, but on-purpose.




A5800s/A5500s - rrpp/iBGP - metroE
Occasional Contributor

Re: 5500G-EL discards on cascade ports

I'm thinking that the discards are there purely because the ports are being blocked by spanning tree protocol.


3Com Network Director does not show any problem in this area

Occasional Visitor

Re: 5500G-EL discards on cascade ports

Just to flesh this out a bit


2,500-2,800 discards per minute

Two switches connected via cascade ports A1->B2 and B1->A2 

CPU rarely drops below 40% on the 5 minute counter

Buffers seem to be 97-98% used at any moment in time (querying OID

Ethernet ports showing no real load to speak of (mostly sub 1%)

Servers have two network cards in set up as a team, one card to each switch


Couple of theories so far, buffers - just not enough of them and ingress/egress with the multihomed servers and traffic being sent accross the switches when it thinks they are 'local'.


So, overall

1: is the amount of discards anything to be worried about

2: how do we find out what they are? (and how can we clear them?)

3: is it just running out of buffers? 




Neil Read
Occasional Visitor

Re: 5500G-EL discards on cascade ports

Did you resolve this issue?


I also have two 3com 5500g switches with high recieve discards.


Not sure if it's missing VLANS on some of the ports, faulty cables or just miss reporting within Solarwinds.

Trusted Contributor

Re: 5500G-EL discards on cascade ports

Hi all


Thats a normal behavior in xrn/irf-ring-topology. Let me explain:


In a ring topology you have redundant ways. XRN/IRF send hardbeat-packet in both directions for redundancy checks. the second one receiving on the master device will be dropped. unfurtunatly this drop is reported as discarded by FFP (Fast Forwarding Processor) => display packet-drop.


I discussed this several times with R&D and tech support, but it doesnt seam important for them. "It works as designed"




H3CSE, MASE Network Infrastructure [2011], Switzerland