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Duplicate IP addresses on a LAN

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Special Forums IP Networking Duplicate IP addresses on a LAN
# 1  
Old 03-25-2006
Duplicate IP addresses on a LAN
This might be a silly question....

I was wondering what would happen if a user connected on a LAN set up their IP address to match the IP of an existing computer on the LAN. Particularly if both computers were hosting web servers.

Is there a way to change the system boot of a comp to make sure that a user doesnt accidentally set their IP address to match an existing one?
# 2  
Old 03-27-2006
Is it possible to use DHCP
# 3  
Old 03-28-2006
Most kernels will warn at the console if the IP address assigned in a duplicate; ifconfig will do an arp lookup on any address it's asked to assign via the interface it's asked to assign to.

i.e. as you (or your rc2.d scripts) execute 'ifconfig eth0 192.168.1.10 ... '
ifconfig will do an arp via eth0 (all layer2, no IP required yet) and report something like 'ip address {IP address} in use by {MAC address}' and mark the interface 'down'.

This also applies if your DHCP server has had a bad day and started assigning its pool for a second (or third) time.
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