High Switch Port utilization

Answered Question
Nov 10th, 2008
User Badges:

I have switch-A 3524, fa0/9 is connected to switch-B 2924 fa 0/22. We are observing the output utilization on switch-A fa 0/9 is very high(98.94) and at switch-B 2924 fa 0/22 Input utilization is high(99.06) and there is no other port on switch-B with not more than 10% utilization.


3524, fa 0/9 ----> 2954 fa 0/22


Switch-A interface:-



FastEthernet0/9 is up, line protocol is up

< Deleted >

reliability 255/255, txload 219/255, rxload 14/255

< Deleted>

1005 input errors, 1005 CRC, 0 frame, 1134 overrun, 1134 ignored

0 watchdog, 75042 multicast


I appreciate if some one can help me to find what could be the reason.

Correct Answer by glen.grant about 8 years 6 months ago

Those are really old switches so the best way to look at those ports would be to use "sh controllers ethernet-controller fastethernet x/x " to get a good look at all the stats. If you don't have a way to look at the layer 3 info via netflow or other tools then you may have use a packet analyzer and span those ports to get a look at the traffic. To clear the ethernet controller stats it is "clear controllers ethernet-controller " .

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 3.5 (2 ratings)
Loading.
Giuseppe Larosa Tue, 11/11/2008 - 00:16
User Badges:
  • Super Silver, 17500 points or more
  • Hall of Fame,

    Founding Member

Hello Gorkal,

the link fa0/9 is the uplink for the second switch switch-B this should explain why you see an high usage of this port: all packets for users connected to switch-B have to be sent out Switch-A:f0/9.

You say there is no other port on SwitchB with more then 10% usage: these are user ports.

Suppose there are ten users each at 10% : a 90% of FE is needed to go on SwitchA:f0/9 to provide the packets to the users.


If you want to find out the associated traffic for each user you can:

on the router / multilayer switch that provides a default gateway to users configure

int fas0/0

ip accounting output


you can then look at statistics with sh ip accounting on the router.

If you find one user with a lot of conversations with internet for example and high traffic volume that means the PC is running some peer-to-peer software.


If all the traffic is legimitate you are facing a limitation of the current setup: you should consider to create an etherchannel link of 2 or 4 FE between the two switches in order to provider more inter-switch bandwidth.

In the mid / long term you could think to change the switches using newer ones with Gigabit uplinks



Hope to help

Giuseppe


darren-carr Tue, 11/11/2008 - 00:18
User Badges:

Hi,


How do you have the speed and duplex of the interfaces in question configured?


Is the inter-switch connection defined as a trunk?


Can you do a 'sh run int fa 0/9' and 'sh run int fa 0/22' on the other switch and post this?


Thanks

Correct Answer
glen.grant Tue, 11/11/2008 - 05:07
User Badges:
  • Purple, 4500 points or more

Those are really old switches so the best way to look at those ports would be to use "sh controllers ethernet-controller fastethernet x/x " to get a good look at all the stats. If you don't have a way to look at the layer 3 info via netflow or other tools then you may have use a packet analyzer and span those ports to get a look at the traffic. To clear the ethernet controller stats it is "clear controllers ethernet-controller " .

Actions

This Discussion