3560-G High switchport utilization

[david-flores]

Dear Experts,

Need some guidance in troubleshooting high switchport utilization which seems to only happen on my 100mb ports and also when the Symantec backup jobs run.  The switch is a 3560G-48 in a DMZ behind a Checkpoint firewall.  We are only using about 23 of the 48 ports, and of those 23, 5 are running servers at 100mb while the rest are running at 1gb.  The 5 100mb ports will spike up to 100% utilization while the 1gb ports are less than 20% utilized.  Not all these servers back up at the same time,  so I cannot figure out why all the 100mb ports are sitting at 100% for a period of time.  Is it even possible that this is because of an oversubscription issue?  The stats on the switch only show about 2% during this time.  Any guidance on troubleshooting this would be appreciated.  Not sure if I need to consider a higher end switch since this switch is more of an access layer model.

Thanks

[Leo Laohoo]

so I cannot figure out why all the 100mb ports are sitting at 100% for a period of time.

Can't those negotiate to 1Gb?

[david-flores]

Unfortunately, No.  Some of these are an older model Firewall, and some other appliances that don't support 1Gb.

[Leo Laohoo]

Can you post the following commands please:

1.  sh interface

2.  sh controller util (maybey do this a few times as this is real-time)

[david-flores]

Right now it is sitting at 0%, but I will check these stats again when the backups run later this evening.

Thanks

[Joseph W. Doherty]

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Posting

You have gig ports running less than 20% (200 Mbps) and these outnumber the ports running at 100 Mbps better than 3:1 (18 vs. 5).  It also only happens whan a backup job runs.  I would say, yes, there might be an oversubscription issue.  Just one gig port running at 20% would oversubscribe a 100 Mbps port.

Confirmation is a bit difficult on a 3560 since it doesn't, I believe, provide flow stats.

If this high utilization is causing performance issues, beyond just your concern about the high utilization, you might activate QoS features, and deprioritize the backup stream as "background".  In this way, 100% port utilization shouldn't much adversely impact traffic other then backup traffic.

[david-flores]

If oversubscription is this issue here, and other than implementing QOS, would a jump in hardware to like a 3750, or 4900 be a solution to help with an oversubscription issue?

[Joseph W. Doherty]

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose.  Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind.  Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

Not if the oversubscription is happening on edge ports, themselves.  You would need ports with higher bandwidth, and that's already the issue since you have gig ports on the switch but the congested host devices don't support it.  You might find that host device might support some form of port channeling with the switch, but odds are against that.