Identifying Sources of Performance Problems

donemore2003
donemore2003 used Ask the Experts™
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I have a network where people are complaining about performcace problems.  When I do ping test pings to remote locations, I sometimes get dropped packest.  There is plenty of bandwidth serving the site; below 30 % utilization even at the times the users compalin about performance.  I ahve a 3350 configures as a L3 with multiple vlans.  2 of the switches are trunked to this L3.  The 3rd access switch is connected to access switch 1 and 2.  One of the uplink on this switch is blocking.  None of the other switches has bolcked ports.  my configs are as shown on the attached worksheet.  I see that on some of the trunked ports, there are prots configures as desirable and the other as trunk but they still forma trunk between the 2.  Does this really cause problems?

There are some QoS configurations, (still learnig QoS) and don't really understand it.  I see the configurations are not consistent, could this be a cause for concern possibly causing performance problems beyond just ping?

Also see the access list configured on the L3.  I don't see anything else configured on the L3 besides these 2 lines as it regards to access list.  Is this really serving a purpose?  

All access ports are configured as shown on attached worksheet.

Note:  The L3 is a VTP server and the rest vtp clients.


I have looked just abou everywhere and don't seem to find a problem.  

Any insite as to what to look for will be helpful.

Thanks


Book1.xlsx
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Why are you trunking on the access ports? you should change them to switchport mode access, and then enable portfast on them. it best if you are trunking to have both ports setup the same, so if you are runing dynamic trunking protocol (DTP) it's best to have it setup on both ends. I favor shutting it off and only trunking where you need to. so on all trunk ports do "switchport mode trunk". I would say for the qos you want to make the setup the same on all switches, on some you are trusting cos and others you are trusting dscp. you also have them mapped to different queues on a couple of different ports. If this is a lan and you don't have bandwidth problem you don't need qos enabled. either way a quick way of fixing your qos is to enable auto qos. it will set it up for cisco's out of the box qos.
Commented:
Well, unless your network is really overloaded, chances are that the QoS is not the issue.
There are numbers of possibilities for the problems you describe.

Here are a few things you should check out :
- spanning tree :it looks like you have that taken care of, but it's worth double checking configs and logs. If it's flapping or there is a gap in the config somewhere, the loop could be the problem (do you really need it ? you could try physically disconnecting it for a while and see if it's better)
You didn't mention if your access switchs were cisco too, if not, make sure you are not using cisco-specific multiple spanning tree features.

- Check all the counters and  logs on your switches, see if there's something fishy there, like large number of errors of any kind.
It might be worth it to install a snmp monitoring system (ie nagios, or prtg) to monitor that and the bw usage patterns over a couple of days/weeks

- Vlans could be another issue too.
The switchport mode dynamic desirable works in a full (recent) cisco environment, but you might aswell spend five minutes and manually (properly ? ;-) config your trunk ports and vlan allowed.
It will also save you some headaches down the line if you plug something that can't speak ISL (even cisco stuff.. ie one of my PIX can't.. I don't even think it can do DTP by default)

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Commented:
flakk:

I am using all cisco switches; 3550 models.  The trunk link uplink trunks are not flapping.  I see that at times int fastE interfaces going up/down 3 - 4 times before the port stabilizes.  I am not too sure if that is normal or not.  

see example:

Oct 26 11:59:55: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/11, changed state to down
Oct 26 12:00:00: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/11, changed state to up
Oct 26 12:00:10: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/11, changed state to down
Oct 26 12:00:15: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/11, changed state to up
Oct 26 12:42:12: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/10, changed state to down
Oct 26 12:42:17: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/10, changed state to up
Oct 26 12:42:27: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/10, changed state to down
Oct 26 12:42:31: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/10, changed state to up
Oct 26 12:56:00: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/15, changed state to down
Oct 26 12:56:04: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/15, changed state to up
Oct 26 12:56:14: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/15, changed state to down
Oct 26 12:56:19: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/15, changed state to up
Oct 26 13:21:54: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/8, changed state to down
Oct 26 13:21:59: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/8, changed state to up
Oct 26 13:22:08: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/8, changed state to down
Oct 26 13:22:12: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/8, changed state to up
Oct 26 14:19:56: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/9, changed state to down
Oct 26 14:20:01: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/9, changed state to up
Oct 26 14:20:10: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/9, changed state to down
Oct 26 14:20:15: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/9, changed state to up
Oct 26 14:32:52: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/8, changed state to down
Oct 26 14:32:57: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/8, changed state to up
Oct 26 14:33:13: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/8, changed state to down
Oct 26 14:33:18: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/8, changed state to up
Oct 26 14:33:27: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/8, changed state to down
Oct 26 14:33:31: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/8, changed state to up
Oct 26 15:48:17: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/12, changed state to down
Oct 26 15:48:22: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/12, changed state to up
Oct 26 15:48:32: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/12, changed state to down
Oct 26 15:48:37: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/12, changed state to up
Oct 26 18:15:51: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/6, changed state to down
Oct 26 18:15:56: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/6, changed state to up
Oct 26 18:16:04: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/6, changed state to down
Oct 26 18:16:09: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/6, changed state to up
Oct 26 18:49:51: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/7, changed state to down
Oct 26 18:49:56: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/7, changed state to up
Oct 26 18:50:06: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/7, changed state to down
Oct 26 18:50:10: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/7, changed state to up

When I check the ports, I see no errors at all.

QoS Config:

The 3rd switch is connetced to the other 2 switches.  I have the configs on one side trsting dscp and the other cos; what effect does that have if any.  Still trying to understand QoS.   There are no errors anywhere on the ports; any port.  

If there was a loop, would it be that evident.  There is on port on the 3rd switch that is alternate/blocking.  The rest of the trunk up links are forwarding .





network-layout.docx

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