Lexmark Z2400 Series - Manual (Page 31)

What is a key index?
A wireless access point (wireless router) can be configured with as many as four WEP keys. Only one key is used on
the network at a time, however. The keys are numbered, and the number of a key is referred to as its key index. All
devices on the wireless network must be configured to use the same key index when multiple WEP keys are configured
on the wireless access point (wireless router).
The printer is designed to use the first key. Make sure you have configured all of the wireless devices on your network
to use the first WEP key where you have the option of selecting a key. Make sure the wireless access point (wireless
router) is also configured to use the first key. The first key will usually have an index of 0, though it may be 1 on some
devices.
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