Alg Support - D-Link DSR-150 User Manual

Unified Services Router
Type: The layer 3 Protocol that the service uses. (TCP, UDP, BOTH, ICMP or
ICMPv6)
Port Type: This fields allows to select Port Range or Multiple Ports
ICMP Type: This field is enabled when the layer 3 protocol (in the Type field) is
selected as ICMP or ICMPv6. The ICMP type is a numeric value that can range
between 0 and 40, while for ICMPv6 the type ranges from 1 to 255. For a list of
ICMP types, visit the following URL: http://www.iana.org/assignments/icmp-
parameters.
Start Port: The first TCP, UDP or BOTH port of a range that the service uses. If the
service uses only one port, then the Start Port will be the same as the Finish Port.
Finish Port: The last port in the range that the service uses. If the service uses only
one port, then the Finish Port will be the same as the Start Port.
Port: The port that the service uses.
5.6

ALG support

Advanced > Firewall Settings > ALGs
Application Level Gateways (ALGs) are security component that enhance the firewall
and NAT support of this router to seamlessly support application layer protocols. In
some cases enabling the ALG will allow the firewall to use dynamic ephemeral TCP/
UDP ports to communicate with the known ports a particular client application (such
as H.323 or RTSP) requires, without which the admin would have to open large
number of ports to accomplish the same support. Because the ALG understands the
protocol used by the specific application that it supports, it is a very secure and
efficient way of introducing support for client applications through the router's
firewall.
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