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Firewall Security
Level Services Table
The following information is related to the Firewall options (High, Medium, and
Low) section in the “Using Advanced Setup” chapter of this manual (see page 33).
The types of services and their respective ports are listed in the two right-hand
columns: the “In” column details whether a particular service can be accessed by a
user outside of the network; and the “Out” column details whether a computer on
the Modem’s network can access a particular incoming service.
For example, in the “High Security Level” section below, the http service uses port
80. Since no is listed in the In column, a user outside the Modem’s network cannot
access a computer on the network via the http service; in this case, no computers
on the network can be used as a Web server (i.e., to host a Web site accessible to
outside users). However, since yes is listed in the Out column, all computers on the
Modem’s network can access the Internet via the http port.
If Basic Security is selected in the “Firewall” screen, firewall filtering is based on the
basic NAT firewall.
High Security Level
Service Port In Out
http 80 no yes
dns 53 no yes
ftp 21 no no
telnet 23 no no
smtp 25 yes yes
pop3 110 yes yes
nntp 119 no no
real audio/video 7070 no no
icmp n/a no yes
H.323 1720 no no
T.120 1503 no no
SSH 22 no no
imap 163 yes yes
https 443 yes yes
secure imap 983 yes yes
secur pop3 885 yes yes
F