Performance tuning and diagnosis of eth0?

Discussion in 'Cisco' started by Helmut, Feb 23, 2005.

  1. This is my (simplified) configuration:

    +------------+ +--------+ +-------+
    | server .2 |------| Cisco |----| cable |
    +------------+ +-| 831 | | modem |
    | +--------+ +-------+
    +------------+ |
    | server .11 |--+ |
    +------------+ | | +--------+
    | +-| |
    +------------+ +---| switch |
    | PC .21 |------| |
    +------------+ +--------+

    The speed of the cable modem is limited to 1024 kbit/sec download and
    512 upload, connection to cisco is 10 Mbit ethernet.

    LAN is 100 Mbit including switch and NICs in the machines.

    Unfortunately I configured the LAN to eth0, which is a virtual interface

    interface Ethernet0
    ip address
    ip access-group 112 in
    no ip proxy-arp
    ip nat inside
    no ip route-cache
    no cdp enable
    hold-queue 32 in

    FastEthernet1 to 4 have no IP configured.

    interface FastEthernet1
    no ip address
    duplex auto
    speed auto

    Now the measured speeds with bing are:
    PC .21 to Cisco .1 6 Mbit
    PC .21 to Server .2 8 Mbit
    PC .21 to server .11 45 Mbit
    Server .11 to Cisco .1 10 Mbit
    Server .2 to Cisco .1 40 Mbit

    As I watched full speed to good connected sites with my old router, and
    now with the Cisco between 400 - 700 kbit, I want to do the best possible.

    Do I understand right, that I have to configure the FastEthernet
    interfaces? This will need splitting into subnets too?

    What is the appropriate manual for interfaces configuration and tuning?


    Helmut Wollmersdorfer
    Helmut, Feb 23, 2005
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  2. No! On the 8xx series the fastethernet interfaces exist ONLY to set
    MAC-level parameters of the internal switch like speed and duplex.

    That said, make sure the autonegotiation worked and that you don't have a
    duplex mismatch between the router and switch (try manual settings). Some
    switches are not soo good at autonegotiation. I tore my hair out on a
    performance problem for over a week until I discovered that the cheapie
    disposable ethernet switch was failing is a very subtle way. So try a
    switch swap if practical.
    Phillip Remaker, Feb 24, 2005
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