performance problem with my home network

[joehu@yahoo.com]

Dear network gurus,

I have a big performance problem with my home network. I have a linux box (debian potato), which serves as router, directly connected to the provider's network via cable modem. It uses NIC eth0. NIC eth1 connects to a hub. A second machine, running windows ME, is also connected to the hub. Here's the routing table of my linux router(192.168.1.3):

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.1.0     192.168.1.3     255.255.255.0   UG    0      0        0 eth1
192.168.1.0     0.0.0.0         255.255.255.0   U     0      0        0 eth1
146.115.74.0    0.0.0.0         255.255.254.0   U     0      0        0 eth0
0.0.0.0         146.115.74.1    0.0.0.0         UG    0      0        0 eth0

The linux box runs a script "ipmasq" to set up firewall rules, which is attached at the end of the message.

The performance is great on the linux box. The download speed is 800KB/s. However, the 2nd machine (windows ME) is extremely slow. The download speed is about 50KB/s. The 2nd machine is configured as static IP 192.168.1.2 and uses the linux box as default gateway. Does anybody know what's wrong with it? Is it a routing problem or firewall/ip masquerading issue?

Thank you in advance.

joe

================== script ipmasq =================
#!/bin/sh
########################################################################
### FILE:       /etc/init.d/ipchain
### PURPOSE:    Start/Stop IP chains (masquerade) service
### Thanks to Jason Kissinger <jlk@windchill.com> for some tweaks
########################################################################

NAME=$0

case "$1" in
  start)
    echo -n "Starting IP chains (masq) support... "

    # flush the rule tables. 
    /sbin/ipchains -F input 
    /sbin/ipchains -F forward 
    /sbin/ipchains -F output 

    # set the MASQ timings and allow packets in for DHCP configuration. 
    /sbin/ipchains -M -S 7200 10 60 
    /sbin/ipchains -A input -j ACCEPT -i eth0 -s 0/0 68 -d 0/0 67 -p udp 
    /sbin/ipchains -A input -j ACCEPT -i eth0 -s 0/0 -d 0/0 -p all
    
    # default policy is deny
    /sbin/ipchains -P forward DENY

    # Block Windows "whohas" traffic to prevent spurious dialling...
    /sbin/ipchains -A forward -j DENY -p tcp -s 0.0.0.0/0 137:139
    /sbin/ipchains -A forward -j DENY -p udp -s 0.0.0.0/0 137:139

    # allowing ip forwarding from internal host to external net
    echo 1 > /proc/sys/net/ipv4/ip_forward
 
    # provide masquerade services for the local machines
    /sbin/ipchains -A forward -s 192.168.1.0/24 -d 0.0.0.0/0 -j MASQ
 
    # load forwarding modules for special services. 
    /sbin/insmod ip_masq_cuseeme
    /sbin/insmod ip_masq_ftp
    /sbin/insmod ip_masq_irc
    /sbin/insmod ip_masq_quake
    /sbin/insmod ip_masq_raudio
    /sbin/insmod ip_masq_vdolive

    echo 1 > /proc/sys/net/ipv4/ip_dynaddr

    echo "Done."
    ;;

  stop)
    echo -n "Stopping IP chains (masq) support... "
    /sbin/rmmod ip_masq_cuseeme
    /sbin/rmmod ip_masq_ftp
    /sbin/rmmod ip_masq_irc
    /sbin/rmmod ip_masq_quake
    /sbin/rmmod ip_masq_raudio
    /sbin/rmmod ip_masq_vdolive

    echo 0 > /proc/sys/net/ipv4/ip_dynaddr
    echo "Done."
    ;;

  *)
    echo "Usage: /etc/ppp/$NAME {start|stop}"
    exit 1
    ;;
esac

exit 0