troubles listening for two external ip addresses...

[Oliver George]

Hello,
I have a debian firewall, it runs the current stable debian and uses 
out-of-the-box ipmasq.
I wanted to make the firewall listen for a second IP address on the 
external ethernet card so i changed my /etc/network/interfaces as 
indicated below.
My problem is that I people inside the firewall don't seem to be able to 
access the internet, but if i just type 'ifdown eth0:1' everything 
returns to normal.

I'd really appreciate any suggestions,
Thanks Oliver.
===OLD =================
iface eth0 inet static
      address 23.61.247.34
      netmask 255.255.255.0
      network 23.61.247.0
      broadcast 23.61.247.255
      gateway 23.61.247.1
iface eth1 inet static
      address 192.168.1.1
      netmask 255.255.255.0
      network 192.168.1.0
      broadcast 192.168.1.255
      gateway 23.61.247.41
===NEW=================
iface eth0 inet static
      address 23.61.247.34
      netmask 255.255.255.0
      network 23.61.247.0
      broadcast 23.61.247.255
      gateway 23.61.247.1
iface eth0:1 inet static
       address 23.61.247.35
      netmask 255.255.255.0
      network 23.61.247.0
      broadcast 23.61.247.255
      gateway 23.61.247.1
iface eth1 inet static
      address 192.168.1.1
      netmask 255.255.255.0
      network 192.168.1.0
      broadcast 192.168.1.255
      gateway 23.61.247.41