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  • Latency on network after installing new switch

    I have 3 cisco express 500 switches. 2 24 port 10/100 switches and 1 12 port 10/100/1000 switches.

    The 12 port is new, got it for the servers to sit on and get their 1Gbps speed, we ran out of room on the 2 24 port switches. There is only 5 servers on this switch, 5 ports are open and 2 are used for uplinking to the other switches.

    Users have noticed a lot of latency on their applications that talk to these servers. If I go to the server and switch it from Auto to 100Mbps/Full it is back to normal.

    Why are the users experiencing delays when the servers are running at 1Gbps?

    The only other troubleshooting I have tried was to set the switch port that the server is on to 1000 / Full and the server to auto negotiate 1000, that didn't help.

    We have about 24 users, I have 12 users on 1 switch and 12 on the other.

    Then printers on 1 of those switches and our older servers and networking equipment (spam filter, firewall, etc..) on the other. I split the users up to keep the uplinks from bottle necking.

    We have 1Gb uplinks to the main switch, and all of the users are 100Mbps (since they are on the 10/100 switches)

  • #2
    Re: Latency on network after installing new switch

    It does initially sound like a duplex mismatch (or similar) have you run something like wireshark to see what is happening on a server?
    cheers
    Andy

    Please read this before you post:


    Quis custodiet ipsos custodes?

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    • #3
      Re: Latency on network after installing new switch

      Auto negotiations are known to fail for different reasons one of which could be conforming to the ever changing standards by the manifacturers.
      Although many claim now that this is a myth.
      Anyway, to successfully Autonegotiate, it should be set on both sides of the link.
      If it fails just hard set (Equal value) the speed and duplex mode in both ends and you shouldn't have a problem.
      Caesar's cipher - 3

      ZKHQ BRX HYHQWXDOOB GHFLSKHU WKLV BRX ZLOO UHDOLVH LW ZDV D ZDVWH RI WLPH!

      SFX JNRS FC U6 MNGR

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      • #4
        Re: Latency on network after installing new switch

        I know my description is kind of long, but in there I stated that i tried setting the switch to 1000 / Full Duplex and the server to auto negotiate 1000 (the option of 1000 / Full on the server is not available, I think because 1000 Mbps speeds wont go half from what I hear)

        But anyway, when I tried that it didn't seem to make a difference from when it was set to auto/auto.

        I need to schedule some after hours time and try it again though. If anyone else has any other Ideas I'm open to suggestions.

        Thank you both for your responses.

        And no Andy, I have not had a chance to run wireshark on a server. I will probably leave that as a plan B if after I change all the speed/duplex options on the servers/switch and it still hangs up.

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        • #5
          Re: Latency on network after installing new switch

          you may have already tried this, but have you enabled spanning tree (STP) on the switchports?

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          • #6
            Re: Latency on network after installing new switch

            Yeah I think it is enabled by default. These cisco express switches are a little less configurable than the standard catalysts. Unless anyone knows that for sure, I have not had much experience with these.

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            • #7
              Re: Latency on network after installing new switch

              Can you copy and paste the running config to the forum thread.

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              • #8
                Re: Latency on network after installing new switch

                I dont believe these switches are configurable in that way, its only webgui.

                I did find something out that was interesting, I read that a crossover cable for 1000Mb is different than one for 100Mb, Im sure that the crossovers i have linking the switches is one made for 100Mb.

                Any one have any idea how good the auto-mdix is? Should I just uplink them with straight patches and enable automdix or just go ahead and make the 1Gb standard crossovers?

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                • #9
                  Re: Latency on network after installing new switch

                  I'm not so sure there is a different crossover for gig links. Someone may have been referring to CAT5 vs CAT6, but the cable's pinout is the same. Auto-mdix is great as long as you aren't using trunking. When I tried on a 3750, auto-mdix stopping functioning as soon as a port was configured as a trunk. I personally would disable auto-mdix and use the proper cable type.

                  I would also want to ensure this isn't a spanning tree issue. How are the switches hooked together? Your topology determines spanning tree requirements, so it would help alot to know your network setup.

                  Do you know what the utilization on your uplinks is? If utilization is really high, you may want to port-channel.
                  -Tim

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                  • #10
                    Re: Latency on network after installing new switch

                    Based on the fact that changing the speed/duplex settings seems to resolve the issue I would say that it isn't an STP issue as you would have issues (looping) regardless of the speed/duplex settings. You can be almost 100% assured that STP is enabled by default with the default settings of Bridge ID of 16384 on all three switches, which means that the switch with the lowest MAC address (the oldest switch) will be the Root Bridge. Are you using cat5e cables to link the switches together and to link the servers to the switch? Are the cables new? Have you tested the cables? Also, I personally would recommend using auto-MDIX and a straight-through cable to link the switches.

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                    • #11
                      Re: Latency on network after installing new switch

                      I agree that this isnt a spanning tree issue.. but ill tell you how i have them connected...

                      Switch 1 is the 12 port 10/100/1000
                      Switch 2 is 1 of the 24 port 10/100
                      Switch 3 is the other 10/100 24 port

                      Port 11 on Switch 1 has a crossover going to G1 of Switch 2
                      Port 12 on Switch 1 has a crossover going to G2 of Switch 3

                      thats it...

                      I have the uplinks set to 1000 / Full as of right now no auto and mdix off.

                      as per the utilization graphs on the switch these uplinks are not over loaded.... i have 12 users on each switch... 5 servers on switch 1... there is some printers and other older servers that are on their way out of the network on switch 2 and 3.

                      of the servers 1 is exchange 1 is a dc and sql and the other 3 are sql

                      and not everyone uses those sql data bases maybe 5-10 my guess.

                      What I just did was change the uplink cables, i made a cable like i read about that was for gigabit... it seems to work anyway that was the first ive heard about it but o well

                      i found that 2 servers had cat5 cables so i replaced those with 5e and i didnt notice a difference. i just changed the port setting on the switch to 1000/full and made all servers auto neg. 1000

                      everyone is gone im the only one here. so noone is using anything.

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                      • #12
                        Re: Latency on network after installing new switch

                        Well STP is without a doubt not a problem as you don't have the switches redundantly connected. Currently you have only one path from switch to switch to switch and only one path to any host device connected to the switches. Have you tried connecting a computer to the server switch to see if there's any difference? If it's better than you can assume the switch links are the problem, if it's not then you can assume the server switch is the problem.

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                        • #13
                          Re: Latency on network after installing new switch

                          I will try that now.

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                          • #14
                            Re: Latency on network after installing new switch

                            Also, if it's no better then connect two computers to the server switch and test them against eact other, if they're OK then you can concentrate on the servers being the problem. If they're bad with each other than that pretty much confirms the switch as the problem.

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                            • #15
                              Re: Latency on network after installing new switch

                              It came right up....

                              so Im going to try putting different cables in the uplinks...

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