User guide

Configure Serial Port Settings
Chapter 1 Command Line Configuration Tasks 21
Filters for PPP Connections
Filters are used to manage and control Point-to-Point Protocol (PPP)
connections. You can design a filter to do any of the following:
• Bring up a connection.
• Allow certain types of packets to use the connection and keep certain
types of packets from using it.
• Keep up a connection.
• Send a message to the log file when a specified event occurs on the
connection.
For example, you might develop a filter that brings up a connection on an
outbound port only when device server handles a packet carrying a
particular destination IP address.
The “set user” command has options that define how a filter functions, that
is, whether it is the type of filter that accepts or blocks packets, brings up a
connection, keeps up a connection, or sends a message to the log file. The
following table describes each of the set user options related to filtering.
When changes to filter definition settings take effect
The “set filter” command can be used at any time to change and display
filters. However, the results of any changes to filter definition settings take
effect on subsequent PPP connections only. Any PPP connections
established prior to a given filter change will continue to operate using the
previous filter definition settings. For the new filter settings to take effect,
existing PPP sessions must be terminated and reestablished.
More information on filters
For more information about using filters, see "set filter" on page 111, and
"set user" on page 230.
“set user”
Option
Description Example
passpacket Causes a packet to be
passed or blocked.
Filter causes incoming packets from
an IP address to be accepted and
packets from all other IP addresses
to be blocked.
keepup Causes the idletimeout
timer to be reset and a
connection maintained.
Filter that causes the connection to
be maintained as long as there is
any packet traffic except RIP
packets.
bringup Causes the Digi device to
establish a connection.
Filter that causes an outgoing
connection to be initiated whenever
a packet specifying a particular IP
address is handled.
logpacket Causes the Digi device to
send a message to the
log file.
Filter that notifies the log anytime an
ICMP packet is handled.