Multilink traffic question

Discussion in 'Cisco' started by carefree, Feb 15, 2010.

  1. carefree

    carefree

    Joined:
    Feb 15, 2010
    Messages:
    3
    I have a Cisco 2600, two T1s on the Serial interfaces bundled into a multilink. The transmit and receive figures are rather puzzling to me. I'm wondering if they are normal or idicative of a problem.

    In summary, my observation is that the multilink transmit load is usually the sum of the two serial txloads while the multilink receive load is usually about half the sum of the two serial rxloads.

    I've even seen it where the multilink receive load is way less than half of what just one of the serial interfaces is showing for rxload.

    Is this normal?
     
    carefree, Feb 15, 2010
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  2. carefree

    carefree

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    Here are some typical stats:

    Serial0/0 is up, line protocol is up
    Hardware is PQUICC with Fractional T1 CSU/DSU
    MTU 1500 bytes, BW 1536 Kbit, DLY 20000 usec,
    reliability 255/255, txload 44/255, rxload 108/255
    5 minute input rate 652000 bits/sec, 116 packets/sec
    5 minute output rate 267000 bits/sec, 141 packets/sec

    Serial0/1 is up, line protocol is up
    Hardware is PQUICC with Fractional T1 CSU/DSU
    MTU 1500 bytes, BW 1536 Kbit, DLY 20000 usec,
    reliability 255/255, txload 44/255, rxload 107/255
    5 minute input rate 647000 bits/sec, 115 packets/sec
    5 minute output rate 266000 bits/sec, 141 packets/sec

    Multilink1 is up, line protocol is up
    Hardware is multilink group interface
    Internet address is xxx.xxx.xxx.xxx/30
    MTU 1500 bytes, BW 3072 Kbit, DLY 100000 usec,
    reliability 255/255, txload 86/255, rxload 106/255
    5 minute input rate 1283000 bits/sec, 222 packets/sec
    5 minute output rate 1039000 bits/sec, 201 packets/sec


    Txloads add up
    s0/0 txload 44/255
    s0/1 txload 44/255
    M1 txload 86/255 <<<< about the sum of the two serial loads

    Rxloads don't add up
    s0/0 rxload 108/255
    s0/1 rxload 107/255
    M1 rxload 106/255 <<<< about half the two serial loads

    5 minute input rates add up
    s0/0 652000 bits/sec
    s0/1 647000 bits/sec
    M1 1283000 bits/sec <<<< about the sum of the two serial rates

    5 minute output rates don't add up
    s0/0 267000 bits/sec
    s0/1 266000 bits/sec
    M1 1039000 bits/sec <<<< almost double the sum of the two serial rates
     
    carefree, Feb 16, 2010
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  3. carefree

    blanken79

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    Honestly, I've never paid much attention to what you are pointing out. I play with multilinks all day for the ISP I work for. As long as both T1's are error free and show up in the bundle, I wouldn't worry about it.

    show ppp mu int multilink1 will show you what links are part of the bundle and if they are up or not.

    You could try changing the load-interval to 30 on both serial interfaces and on the multilink and see if the numbers are closer to what they should be.

    Could have something to do with the serials being 1.5 and the multilink being 3 and how the IOS calculates the interface load.

    Not sure if that is much help, but just a thought.
     
    blanken79, Apr 17, 2010
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