Switching

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  • 1.  Throughput Issue over Etherchannel

    Posted 12-19-2013 07:38

    I was working to establish LAG between two EX4200s. I configured the link speed as 100m on the ae0 & the two participating physical interfaces. Then, I connected two laptops on both switches to check transfer speed via Etherchannel; I got 100 mbps at max. Though, the below output of ae0 interface shows link speed of 200 mbps. Can somebody explain the situation ..... like why I'm not getting double speed?

     

    Laptops are connected over 1G with both switches.

     

     

    root@SPE-MH> show interfaces ge-0/0/12
    Physical interface: ge-0/0/12, Enabled, Physical link is Up
      Interface index: 141, SNMP ifIndex: 528
      Link-level type: Ethernet, MTU: 1514, Speed: 100mbps, Duplex: Auto, BPDU Error: None, MAC-REWRITE Error: None, Loopback: Disabled, Source filtering: Disabled,
      Flow control: Disabled, Auto-negotiation: Enabled, Remote fault: Online
      Device flags   : Present Running
      Interface flags: SNMP-Traps Internal: 0x0
      Link flags     : None
      CoS queues     : 8 supported, 8 maximum usable queues
      Current address: 28:c0:da:36:34:00, Hardware address: 28:c0:da:36:34:0c
      Last flapped   : 2013-12-19 17:13:34 UTC (01:04:30 ago)
      Input rate     : 1536 bps (2 pps)
      Output rate    : 1024 bps (1 pps)
      Active alarms  : None
      Active defects : None
     
      Logical interface ge-0/0/12.0 (Index 113) (SNMP ifIndex 529)
        Flags: 0x0 Encapsulation: ENET2
        Bandwidth: 10mbps
        Input packets : 5491
        Output packets: 204
        Protocol aenet, AE bundle: ae0.0
     
    {master:0}
    root@SPE-MH> show interfaces ge-0/0/13
    Physical interface: ge-0/0/13, Enabled, Physical link is Up
      Interface index: 142, SNMP ifIndex: 530
      Link-level type: Ethernet, MTU: 1514, Speed: 100mbps, Duplex: Auto, BPDU Error: None, MAC-REWRITE Error: None, Loopback: Disabled, Source filtering: Disabled,
      Flow control: Disabled, Auto-negotiation: Enabled, Remote fault: Online
      Device flags   : Present Running
      Interface flags: SNMP-Traps Internal: 0x0
      Link flags     : None
      CoS queues     : 8 supported, 8 maximum usable queues
      Current address: 28:c0:da:36:34:00, Hardware address: 28:c0:da:36:34:0d
      Last flapped   : 2013-12-19 17:17:35 UTC (01:00:39 ago)
      Input rate     : 1024 bps (1 pps)
      Output rate    : 1024 bps (1 pps)
      Active alarms  : None
      Active defects : None
     
      Logical interface ge-0/0/13.0 (Index 114) (SNMP ifIndex 531)
        Flags: 0x0 Encapsulation: ENET2
        Bandwidth: 10mbps
        Input packets : 5544
        Output packets: 184
        Protocol aenet, AE bundle: ae0.0
     
    {master:0}
    root@SPE-MH> show interfaces ae0
    Physical interface: ae0, Enabled, Physical link is Up
      Interface index: 177, SNMP ifIndex: 152
      Link-level type: Ethernet, MTU: 1514, Speed: 200mbps, BPDU Error: None, MAC-REWRITE Error: None, Loopback: Disabled, Source filtering: Disabled,
      Flow control: Disabled, Minimum links needed: 1, Minimum bandwidth needed: 0
      Device flags   : Present Running
      Interface flags: SNMP-Traps Internal: 0x0
      Current address: 28:c0:da:36:34:00, Hardware address: 28:c0:da:36:34:00
      Last flapped   : 2013-12-19 17:13:36 UTC (01:05:30 ago)
      Input rate     : 3904 bps (3 pps)
      Output rate    : 3904 bps (3 pps)
     
      Logical interface ae0.0 (Index 68) (SNMP ifIndex 153)
        Flags: SNMP-Traps 0x0 Encapsulation: ENET2
        Statistics        Packets        pps         Bytes          bps
        Bundle:
            Input :             0          0             0            0
            Output:             9          0           609            0
        Protocol eth-switch
          Flags: Trunk-Mode
     
    {master:0}
     


  • 2.  RE: Throughput Issue over Etherchannel

    Posted 12-20-2013 12:58

    Are you sure links full dublex? 



  • 3.  RE: Throughput Issue over Etherchannel

    Posted 12-21-2013 11:59

    What is the link speed of the laptop NIC? If you change the the speed on the lag and the member links back to 1g, does the max speed for the laptops change?

    I bought a laptop and though it was a 1 g link but it was not, only 100mb.



  • 4.  RE: Throughput Issue over Etherchannel
    Best Answer

    Posted 12-21-2013 17:47

    The traffic between two computers separated by a LAG is limited to the bandwidth of one of the links that makes up the LAG. The switch hashes the ip addresses or mac addresses of the two computers to determine which member of the LAG to send all of the traffic across, thereby limiting the maximum traffic between two computers.  Depending upon the result of the hash, a conversation between two different computers would use a different member of the LAG, and would not effect the bandwidth available to the first two computers.



  • 5.  RE: Throughput Issue over Etherchannel

    Posted 12-21-2013 17:48

    A single flow of traffic between two devices will never exceed more than one physical link using a LAG.  

     

    Try running multiple sessions (eg: file transfers) between the two devices, and one of other these flows may hash across to the unused link.

     

    Failing that, plug more machines in (or run up more VMs with different IP/MAC addresses) and you should be able to utilise the entire link.



  • 6.  RE: Throughput Issue over Etherchannel

    Posted 12-22-2013 06:33

    Thanks Dfex & RSpellman!

     

    Just to add up here:

     

    I, then tested the LAG between EX4200 & C3560X and found the same results. Transfer speed touched 300 mbps as soon as I set the speed of participating interfaces to 1g.  This transfer was between two laptops with one connected to 3560X & the other with EX4200.

     

    Then, I brought in another laptop. Mine was connected to C3560X & the other two with EX4200 with in same VLAN. I started simultaneous file transfers with both of those laptops but the speed didnt cross 100m mark. (participating interfaces of LAG on both switches had their speed re-set to 100m).