Linksys HPN100 User Manual page 40

Telephone Cable
The telephone cables you use can be either crossed over or straight-through.
Standard telephone cables like the ones you use everyday in your home should
do the job.
Note: If you are only sharing Internet access between 2 PCs, you can connect
your modem directly to your HomeLink Card using a standard telephone cable.
However, if you are sharing Internet access among more than two computers, it
is strongly recommended that you obtain a two-way splitter for your phone
jack, or that you find another wall phone jack for your modem connection.
Forcing the HomeLink Phoneline + 10/100 Network PC Card to supply modem
data from the Internet to multiple computers may result in an unstable or failed
network connection.
page 37