Motorola Netopia 3342N - Manual (Page 177)

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Policy-based Routing using Filtersets
Netopia Embedded Software Version 7.7.4 offers the ability to route IP packets using criteria other than the
destination IP address. This is called policy-based routing.
You specify the routing criteria and routing information by using IP filtersets to determine the for warding
action of a par ticular filter.
You specify a gateway IP address, and each packet matching the filter is routed according to that gateway
address, rather than by means of the global routing table.
In addition, the classifier list in a filter includes the TOS field. This allows you to filter on TOS field settings
in the IP packet, if you want.
To use the policy-based routing feature, you create a filter that
for wards the traffic.
• Check the Forward checkbox. This will display the Force Rout-
ing options.
• Check the Force Route checkbox.
• Enter the Gateway IP address in standard dotted-quad nota-
tion to which the traffic should be for warded.
• You can enter Source and Destination IP Address(es) and
Mask(s), Protocol Type, and Source and Destination Port
ID(s) for the filter, if desired.
TOS field matching
Netopia Embedded Software Version 7.7.4 includes two
parameters for an IP filter:
TOS and TOS Mask. Both fields
accept values in the range 0 – 255.
Cer tain types of IP packets, such as voice or multimedia
packets, are sensitive to latency introduced by the network. A
delay-sensitive packet is one that has the low-latency bit set in
the TOS field of the IP header. This means that if such packets
are not received rapidly, the quality of ser vice degrades. If you
expect to route significant amounts of such traffic you can
configure your router to route this type of traffic to a gateway
other than your normal gateway using this feature.
The TOS field matching check is consistent with source and destination address matching.
If you check the Idle Reset checkbox, a match on this rule will keep the WAN connection alive by resetting
the idle-timeout status.
The Idle Reset setting is used to determine if a packet which matches the filter will cause an “instant-on”
link to connect, if it is down; or reset its idle timer, if it is already up. For example, if you wanted ping traffic
not to keep the link up, you would create a filter which for wards a ping, but with the Idle Reset checkbox
unchecked.