Netopia 4541 User Reference Manual page 61

For example:
To delete a configured subnet, set both the IP address and subnet mask values to 0.0.0.0, either explicitly
or by clearing each field and pressing Return to commit the change. When a configured subnet is deleted,
the values in subsequent rows adjust up to fill the vacant fields.
The subnets configured on this screen are tied to the address serving pools configured on the IP Address Pools
screen, and that changes on this screen may affect the IP Address Pools screen. In particular, deleting a
subnet configured on this screen will delete the corresponding address serving pool, if any, on the IP Address
Pools screen.
IP Address
----------------
#1: 192.128.117.162
#2: 192.128.152.162
#3: 0.0.0.0
#4:
#5:
#6:
#7:
#8:
IP Subnets
Subnet Mask
---------------
255.255.255.0
255.255.0.0
0.0.0.0
IP Setup 8-5