Re: [Q] Virtual hosts and routing...

["David H. Silber" <dhs@orbits.com>]

On Fri, Jun 18, 1999 at 12:28:37PM +0200, Mirek Kwasniak wrote:
> On Thu, Jun 17, 1999 at 04:57:30PM -0500, The Doctor What wrote:
> > However, if I log into the system (usually at 216.178.140.240, eth0:0) and
> > try to ping any of my other virtual ips, I get no response.  I hav
> > included the route -n and ifconfig output as an attachment.  
> 
> Try add routes for your ip-aliases:
> 
> route add -host 216.178.140.240 eth0:0
> ...
> route add -host 216.178.140.224 eth0:14

This is something that has been bothering me for a while.  I want to
thank Doctor What for mentioning the problem and Mirek Kwasniak for the
solution.

Since I have a large number of virtual addresses, I wrote a little
function to perform the ifconfig & route operations together.  As a
bonus side benefit, I no longer have to manually number the virtual
interfaces.  I'm posting the function so that other people can make
use of this refinement.

# IFCOUNTER counts the virtual interfaces.
IFCOUNTER=0

#  Set up a virtual interface.
#
#  Usage:
#    virtualif <Interface> <IP number> <netmask> <broadcast> [reset]
# 
#  Example:
#    virtualif eth0 192.168.246.1 255.255.255.128 192.168.246.127
#    virtualif eth0 192.168.246.2 255.255.255.128 192.168.246.127
#    virtualif eth0 192.168.246.3 255.255.255.128 192.168.246.127
#    virtualif eth1 192.168.246.129 255.255.255.128 192.168.246.255 reset
#    virtualif eth1 192.168.246.130 255.255.255.128 192.168.246.255
#
#  The use of the reset flag starts the virtual interface counter from zero.
#
virtualif() {
  INTERFACE=$1
  IP=$2
  NETMASK=$3
  BROADCAST=$4
  RESET=$5
  
  #  When specified, reset the counter so that a second interface can
  #  have its own series of virtual interfaces.
  if [ ${RESET} ]
  then
    IFCOUNTER=0
  fi
  
  #  Build the virtual interface name string.
  VIRTUAL=${INTERFACE}:${IFCOUNTER}
  
  #  The point of all of this is to:
  /sbin/ifconfig ${VIRTUAL} ${IP} netmask ${NETMASK} broadcast ${BROADCAST}
  /sbin/route add -host ${IP} ${VIRTUAL}
  
  #  Increment the virtual interface counter.
  IFCOUNTER=`/usr/bin/expr ${IFCOUNTER} + 1`
}


Despite the examples mentioned, I set shell variables for the netmask(s)
and broadcast address(es) to enhance readability and to avoid mistakes
in typing.  I also use shell variables to give names to the IP addresses,
so the calls tend to look like:

WWWORBITSCOM=207.199.167.12
WWWSILBERSOFTCOM=207.199.167.14
virtualif eth0 ${WWWORBITSCOM} ${NETMASK} ${BROADCAST}
virtualif eth0 ${WWWSILBERSOFTCOM} ${NETMASK} ${BROADCAST}


I hope this helps someone,
David H. Silber

-- 
David H. Silber  --   http://www.orbits.com/~dhs/   --   dhs@orbits.com

  For custom software, see:                http://www.SilberSoft.com/
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