High CPU load on Cisco 877 and 878 while downloading

Discussion in 'Cisco' started by lemmerling@gmail.com, Nov 12, 2006.

  1. Guest

    Hi,

    I've this problem with a Cisco 877; if a user is downloading at maximum
    rate for a while, the connection goes bananas.. I can reach the cisco
    to reload it, but there is no more internet-access. The LEDs are as
    normal, except the recieve and send LED aren't blinking... I noticed
    the CPU-load is continues on 100% when downloading at full speed, if
    the download is capped, the CPU-load lowers also.

    I disabled the http-management-thing and tried to remove as much from
    the config as possible. There's only one VPN-tunnel active on the
    router, but it's hardly used.

    This is a 20 mbit ADSL connection while the maximum speed is 14.5 mbit.
    The connection trained at 20 mbit though (seen this myself at the
    privider).

    Used IOS: c870-advipservicesk9-mz.124-6.T2


    The same problem exist with a 878 (also a 12.4.6 IOS). First I thought
    it was a provider thing but it seems not. The 877 is on another line
    and another provider.

    I would say the continues CPU-load is causing this problem, but I'm not
    sure. Anyone experienced something like this?


    TIA

    Jos
    , Nov 12, 2006
    #1
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  2. Charlie Root Guest

    Hi,

    <> wrote in message
    news:...
    > This is a 20 mbit ADSL connection while the maximum speed is 14.5 mbit.
    > The connection trained at 20 mbit though (seen this myself at the
    > privider).
    >


    I have recently tested performance of Cisco 876 router (which is basically
    the same as your 877 but for ADSL-over-ISDN) using Agilent N2X tester. My
    observation is that top performance of this router at small packets is
    roughly 6Mbps, while with large packets it could go a bit higher - slightly
    over 10Mbps. So this is at most half of the line rate you have.

    > The same problem exist with a 878 (also a 12.4.6 IOS). First I thought
    > it was a provider thing but it seems not. The 877 is on another line
    > and another provider.
    >


    Same with 878. I have tested 878 with QoS enabled, the performance decreases
    dramatically - it can't even do 2Mbps on small packets. According to Cisco
    performance datasheet, 870 routers can deliver upto 12.8Mbps and upto 25Kpps
    in ideal conditions and this values can never be exceeded, but will decrease
    as you add features (NAT, firewall, routing, QoS etc.)

    Don't expect anything much greater in this price range of routers. I have
    tested also DrayTek 2800 and 2900 series routers - they're even worse. While
    Cisco 870 ISR routers perform much better as soon as packet size increases
    to 128Byte, with DrayTek packet size has to be at least 768Byte to get
    decent troughput.

    If you use 20Mbps line, you have to get something like Cisco 1800 series
    router.

    Hope this helps.

    Cheers,
    iLya
    Charlie Root, Nov 12, 2006
    #2
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  3. Guest

    Charlie Root wrote:
    > Hi,
    >
    > <> wrote in message
    > news:...
    > > This is a 20 mbit ADSL connection while the maximum speed is 14.5 mbit.
    > > The connection trained at 20 mbit though (seen this myself at the
    > > privider).
    > >

    >
    > I have recently tested performance of Cisco 876 router (which is basically
    > the same as your 877 but for ADSL-over-ISDN) using Agilent N2X tester. My
    > observation is that top performance of this router at small packets is
    > roughly 6Mbps, while with large packets it could go a bit higher - slightly
    > over 10Mbps. So this is at most half of the line rate you have.
    >
    > > The same problem exist with a 878 (also a 12.4.6 IOS). First I thought
    > > it was a provider thing but it seems not. The 877 is on another line
    > > and another provider.
    > >

    >
    > Same with 878. I have tested 878 with QoS enabled, the performance decreases
    > dramatically - it can't even do 2Mbps on small packets. According to Cisco
    > performance datasheet, 870 routers can deliver upto 12.8Mbps and upto 25Kpps
    > in ideal conditions and this values can never be exceeded, but will decrease
    > as you add features (NAT, firewall, routing, QoS etc.)
    >
    > Don't expect anything much greater in this price range of routers. I have
    > tested also DrayTek 2800 and 2900 series routers - they're even worse. While
    > Cisco 870 ISR routers perform much better as soon as packet size increases
    > to 128Byte, with DrayTek packet size has to be at least 768Byte to get
    > decent troughput.
    >
    > If you use 20Mbps line, you have to get something like Cisco 1800 series
    > router.


    I agree that this sounds like too much for an 870 however it is
    worth checking that there is not something amiss.

    Please post:-

    sh run ! < -- please sanitise.

    !sh tech ipmulticast ! < -- produces a password-removed config and not
    ! < -- too much else if you do not have
    m'cast configured

    !when the router is under stress
    sh proc cpu ! < -- first few lines.

    !when it has stopped frowarding traffic
    sh mem ! < -- first few lines
    sh buff ! < -- all
    , Nov 12, 2006
    #3
  4. Guest


    > I have recently tested performance of Cisco 876 router (which is basically
    > the same as your 877 but for ADSL-over-ISDN) using Agilent N2X tester. My
    > observation is that top performance of this router at small packets is
    > roughly 6Mbps, while with large packets it could go a bit higher - slightly
    > over 10Mbps. So this is at most half of the line rate you have.


    oops, my mistake. The other router was this 876.

    But thanks a lot for your clear answer. I tested a little bit yesterday
    and as long as I stay below 80% of CPU-usage ( around 12 mbit
    downloading) the router stays online.

    If you want I can run the tests just to make sure. Maybe later today.


    thanks,

    Jos
    , Nov 13, 2006
    #4
  5. Guest

    Today I called the reseller and he confirmed all this:

    -the maximum routeable traffic (he used other words, but I hope you'll
    understand this...) is for the 800 series 12 mbit.
    -if I want to use the full bandwidth, I need a 1800 series.


    Anyway, thanks for your answers! Maybe I'll put the router in the
    freezer or something, see what happens then... ;-)
    , Nov 13, 2006
    #5
  6. BTw,if the reason why the router "did not remain online" while you were
    moving more data than it can handle, was that its CPU was pegged in
    interrupt mode, then you should be able to reconfigure it so that
    it can provide CPU cycles to process activity ... something like:

    scheduler allocate 3000 1000

    Cheers,

    Aaron

    ---

    ~ Today I called the reseller and he confirmed all this:
    ~
    ~ -the maximum routeable traffic (he used other words, but I hope you'll
    ~ understand this...) is for the 800 series 12 mbit.
    ~ -if I want to use the full bandwidth, I need a 1800 series.
    ~
    ~
    ~ Anyway, thanks for your answers! Maybe I'll put the router in the
    ~ freezer or something, see what happens then... ;-)
    Aaron Leonard, Nov 13, 2006
    #6
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