Access Points

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jny
Occasional Contributor I

Giants on distribution switch ports

In trying to find a cause for thruput issues, I have discovered that all of the distribution switch ports that our AP125s are connected to, are collecting giants. These are cisco cat 2960 switches, and in their docs, to be declared a giant, there should be an accompanying FCS error. We're not seeing those (or at least the counters aren't reporting any) but the giant count grows slowly.

For example: in 1:06 (h:mm), we've collected 33 giants on the switch interface.

The other "odd" part is that the giant count is pretty much identical for all the APs on a given switch. If I clear the counters, they all grow at the same rate:

Port Single-Col Multi-Col Late-Col Excess-Col Carri-Sen Runts Giants
Gi0/1 0 0 0 0 0 0 29
Gi0/2 0 0 0 0 0 0 29
Gi0/3 0 0 0 0 0 0 29
Gi0/4 0 0 0 0 0 0 29
Gi0/5 0 0 0 0 0 0 29
Gi0/6 0 0 0 0 0 0 28
Gi0/7 0 0 0 0 0 0 29
Gi0/8 0 0 0 0 0 0 29
Gi0/9 0 0 0 0 0 0 28
Gi0/10 0 0 0 0 0 0 28
Gi0/11 0 0 0 0 0 0 29
Gi0/12 0 0 0 0 0 0 28

Port Single-Col Multi-Col Late-Col Excess-Col Carri-Sen Runts Giants
Gi0/13 0 0 0 0 0 0 28
Gi0/14 0 0 0 0 0 0 29
Gi0/15 0 0 0 0 0 0 29


Port Align-Err FCS-Err Xmit-Err Rcv-Err UnderSize OutDiscards
Gi0/1 0 0 0 0 0 0
Gi0/2 0 0 0 0 0 0
Gi0/3 0 0 0 0 0 0
Gi0/4 0 0 0 0 0 0
Gi0/5 0 0 0 0 0 0
Gi0/6 0 0 0 0 0 0
Gi0/7 0 0 0 0 0 0
Gi0/8 0 0 0 0 0 0
Gi0/9 0 0 0 0 0 0
Gi0/10 0 0 0 0 0 0
Gi0/11 0 0 0 0 0 0
Gi0/12 0 0 0 0 0 0
Gi0/13 0 0 0 0 0 0
Gi0/14 0 0 0 0 0 0
Gi0/15 0 0 0 0 0 0

Since the switch ports connected to the APs are the ports reporting the giants, it's got to be something coming into the port from the APs, not the switch trying to send giants to the APs.

Switch port and system routing MTU are both set to 1500.

Any ideas? I can't find an MTU command on the controller running config, nor on the AP config. Is there a way to look at gig interface counters on an AP? I'm striking out trying to find that in the user guide. Everything seems to be about the controller ethernet ports.

thanks,

-jny
Jenny Ladd
Carnegie Mellon University
Aruba Employee

Re: Giants on distribution switch ports

This is normal, check out the following post if you'd like to change the way the system works:

http://airheads.arubanetworks.com/vBulletin/showthread.php?t=2058

-awl
Andy Logan, ACDX
Director, Strategic Account Solutions
Aruba Networks
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