Bridge eth0 and eth1

Gertjan Vinkesteijn fed19 at xs4all.nl
Mon Apr 12 09:16:45 UTC 2004


Raymond Day wrote:

> Hi. I have Fedora running as a server. It's working real good. I have 
> 2 ethernet cards on it. One is a 10/100 and the other a 10/100/1000 
> What I would like to do is Bridge them. I like to plug my main PC in 
> to the 1000 NIC and my LAN into the 100 NIC like it is now. I just 
> don't know how to set it up. A ifconfig on the 2 NIC I get this:
>  
> eth0      Link encap:Ethernet  HWaddr 00:0C:F1:97:98:6E
>           inet addr:192.168.101.10  Bcast:192.168.101.255  
> Mask:255.255.255.0
>           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
>           RX packets:207880844 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:118334357 errors:0 dropped:0 overruns:0 carrier:0
>           collisions:0 txqueuelen:1000
>           RX bytes:2494787937 (2379.2 Mb)  TX bytes:1064255721 (1014.9 Mb)
>           Interrupt:5 Base address:0xb400 Memory:ff8ef000-ff8ef038
>  
> eth1      Link encap:Ethernet  HWaddr 00:07:E9:3E:C3:83
>           inet addr:192.168.100.50  Bcast:192.168.100.255  
> Mask:255.255.255.0
>           UP BROADCAST MULTICAST  MTU:1500  Metric:1
>           RX packets:354284112 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:514821395 errors:0 dropped:0 overruns:0 carrier:0
>           collisions:0 txqueuelen:1000
>           RX bytes:2622181163 (2500.7 Mb)  TX bytes:3227626141 (3078.1 Mb)
>           Base address:0xb800 Memory:ff8c0000-ff8e0000
>  
> I like to set it up like this because my PC has a 1000 NIC in it too. 
> This way I can do Ethernet fast from my PC to the sever. But I still 
> like to be on my LAN too.
>  
> I did this:
>  
> brctl addbr mybridge
> brctl addif mybridge eth0
> brctl addif mybridge eth1
> ifconfig eth0 192.168.101.10
> ifconfig eth1 192.168.100.50
> ifconfig mybridge up
>  
> But a brctl show says under enabled no.
>  
> I did not have a monitor, mouse, or keyboard on it. When I started to 
> do this I could not get to it any more. So I put a monitor, mouse and 
> keyboard on it. But I still can't connect to it with Ethernet now.
>  
> I hope some one can help.
>  
> It was working before by using IP tables. But I could not FTP to some 
> things on my LAN then. This is why I like to try and bridge it.
>  
> -Raymond Day
>  

I don't see what the problem is, I used 10M Nic card (3com) to the 
outside world, and a 10/100 Nic (Intel) for my subnet via a simple 
switch. It worked automatically. There is sometimes some hardware driver 
tuning software, what you can download from the manufacturers tite and 
use with Windows or DOS.

I append a goodie pingscript for subnetting on (A)DSL:

#!/bin/bash
#
# check-if-ppp-up
#
# Peter de Freitas aka ghovs <ghovs at plex.nl>
# not-so-fast hack to keep ADSL alive. Include in crontab
#
# example:
# /usr/local/sbin/check-if-ppp-up
# and in /etc/crontab the following line:
# one-min check if ppp0 is up
*/1 * * * * root /usr/local/sbin/check-if-ppp-up 1> /dev/null


# variables

export PPP_INTERFACE=ppp0        # ppp device
export GATEWAY=195.190.242.109        # ip of ppp device
export ADSL_ROUTER=10.0.0.138        # ip of ADSL router

export INTERNAL_INTERFACE=eth0        # interface to LAN (if any)
export INTERNAL_NETWORK=10.0.0.0    # class c used for LAN (if any)
export EXTERNAL_INTERFACE=eth1        # interface to ADSL router
export EXTERNAL_NETWORK=10.0.0.0    # class c used for ADSL router
                    # ext and int class c's -can- be equal

export LOG=/var/log/ppp.log        # logfile


# functions

add_gateway ()
{
  # add default gateway
  echo "check-if-ppp-up: trying to add default gateway..." &&
  route add default gw $GATEWAY 2> /dev/null &&
  echo "check-if-ppp-up: default gateway added." >> $LOG ||
  echo "check-if-ppp-up: failed to add default gateway." >> $LOG
}

start_pppd ()
{
  # start up pppd
  echo "check-if-ppp-up: trying to restart pppd..." >> $LOG &&
  pptp 10.0.0.138 file /etc/ppp/options 1>> $LOG &&
  echo "check-if-ppp-up: $PPP_INTERFACE brought back up." >> $LOG ||
  echo "check-if-ppp-up: failed to bring $PPP_INTERFACE back up." >> $LOG &

  sleep 35 # matches pptp failure timeout

  # add default gateway
  add_gateway
}

raise_ppp ()
{
  # bring up ppp device
  echo "check-if-ppp-up: trying to bring up $PPP_INTERFACE..." >> $LOG &&
  ifconfig $PPP_INTERFACE up 2> /dev/null &&
  echo "check-if-ppp-up: $PPP_INTERFACE brought back up." >> $LOG ||
  echo "check-if-ppp-up: attempt to bring $PPP_INTERFACE back up failed, 
DIY time." >> $LOG

  # add default gateway
  add_gateway
}

timestamp ()
{
  # timestamp for the log
  date >> $LOG
}

endstamp ()
{
 # indicate end of check-if-ppp-up instance (comment out to keep quiet)
 echo "-<->-" >> $LOG
}


# script

# first attempt, in case ppp0 interface is unavailable
# (most likely)
if ! ifconfig | grep $PPP_INTERFACE &&
    # if ppp device is not up
   ! ifconfig $PPP_INTERFACE 2> /dev/null | grep $PPP_INTERFACE > /dev/null;
    # if ppp device does not exist
  then

  timestamp

  # explain problem
  echo "check-if-ppp-up: $PPP_INTERFACE does not exist." >> $LOG;

  # fix problem
  start_pppd

  endstamp


# second attempt, in case only the default gw is missing
# (not too likely)
elif route -n | grep "$GATEWAY 0.0.0.0         255.255.255.255 UH    
0      0        0 $INTERFACE" &&
    # if route to default gateway exists
   ! route -n | grep "0.0.0.0         $GATEWAY 0.0.0.0         UG    
0      0        0 $INTERFACE";
    # if default gateway is not set as such
  then

  timestamp

  # explain problem
  echo "check-if-ppp-up: the default gateway is unset." >> $LOG

  # fix problem
  add_gateway

  endstamp


# third attempt, in case someone did something like 'ifconfig ppp0 down'
# (not likely)
elif ifconfig $PPP_INTERFACE 2> /dev/null | grep $PPP_INTERFACE > 
/dev/null &&
    # if ppp device exists
   ! ifconfig | grep $PPP_INTERFACE;
    # if ppp device is not up
  then

  timestamp

  # explain problem
  echo "check-if-ppp-up: $PPP_INTERFACE exists, but is down." >> $LOG

  # fix problem
  raise_ppp

  endstamp


# fourth attempt, in case someone messed up the routing table
# (hardly likely)
# this -only- tries to get ADSL back up, it does -not- try to fix beyond 
that
elif ! route -n | grep "0.0.0.0         $GATEWAY 0.0.0.0         UG    
0      0        0 $PPP_INTERFACE" &&
    # if default gateway is not set as such
   ! route -n | grep "$GATEWAY 0.0.0.0         255.255.255.255 UH    
0      0        0 $PPP_INTERFACE" &&
    # if route to default gateway does not exist
   ! route -n | grep "$EXTERNAL_NETWORK        0.0.0.0         
255.255.255.0   U     0      0        0 $EXTERNAL_INTERFACE" ||
   ! route -n | grep "$ADSL_ROUTER      0.0.0.0         255.255.255.255 
UH    0      0        0 $EXTERNAL_INTERFACE";
    # if route to ADSL router does not exist
  then

  timestamp

  # explain problem
  echo "check-if-ppp-up: the routing table is not set up correctly." >> $LOG

  # fix problem
  # set route to ADSL router
  if [ "$INTERNAL_NETWORK" != "$EXTERNAL_NETWORK" ];
    then
    route add -net $EXTERNAL_NETWORK netmask 255.255.255.0 dev 
$EXTERNAL_INTERFACE 2> /dev/null &&
    echo "check-if-ppp-up: added route to ADSL router." >> $LOG ||
    echo "check-if-ppp-up: failed to add route to ADSL router, DIY 
time." >> $LOG

  elif [ "$INTERNAL_NETWORK" = "$EXTERNAL_NETWORK" ];
    # if internal and external network are on the same class c
    then
    route del -net $EXTERNAL_NETWORK netmask 255.255.255.0 dev 
$EXTERNAL_INTERFACE 2> /dev/null &&
    route add -host $ADSL_ROUTER dev $EXTERNAL_INTERFACE 2> /dev/null &&
    echo "check-if-ppp-up: added route to ADSL router." >> $LOG ||
    echo "check-if-ppp-up: failed to add route to ADSL router, DIY 
time." >> $LOG
  fi

  # now that the routes are all set, the ppp device can be brought back up
  start_pppd

  endstamp
fi


# changelog

# 05-nov-2001 <ghovs at plex.nl>
# - major overhaul, should function properly at last
# - added three less likely cases of ADSL breakdown, as well as
# - config variables, comments, log messages, functions
# 08-nov-2001 <ghovs at plex.nl>
# - fixed one message not going to $LOG

-- 
Vink





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