Chapter 12 Policy and Static Routes
UAG5100 User’s Guide
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12.4 Policy Routing Technical Reference
Here is more detailed information about some of the features you can configure in policy routing.
NAT and SNAT
NAT (Network Address Translation - NAT, RFC 1631) is the translation of the IP address in a packet
in one network to a different IP address in another network. Use SNAT (Source NAT) to change the
source IP address in one network to a different IP address in another network.
Assured Forwarding (AF) PHB for DiffServ
Assured Forwarding (AF) behavior is defined in RFC 2597. The AF behavior group defines four AF
classes. Inside each class, packets are given a high, medium or low drop precedence. The drop
precedence determines the probability that routers in the network will drop packets when
congestion occurs. If congestion occurs between classes, the traffic in the higher class (smaller
numbered class) is generally given priority. Combining the classes and drop precedence produces
the following twelve DSCP encodings from AF11 through AF43. The decimal equivalent is listed in
brackets.
Metric
Metric represents the “cost” of transmission for routing purposes. IP routing uses hop count
as the measurement of cost, with a minimum of 1 for directly connected networks. Enter a
number that approximates the cost for this link. The number need not be precise, but it
must be 0~127. In practice, 2 or 3 is usually a good number.
OK
Click OK to save your changes back to the UAG.
Cancel
Click Cancel to exit this screen without saving.
Table 76
Configuration > Network > Routing > Static Route > Add/Edit (continued)
LABEL
DESCRIPTION
Table 77
Assured Forwarding (AF) Behavior Group
CLASS 1
CLASS 2
CLASS 3
CLASS 4
Low Drop Precedence
AF11 (10)
AF21 (18)
AF31 (26)
AF41 (34)
Medium Drop Precedence
AF12 (12)
AF22 (20)
AF32 (28)
AF42 (36)
High Drop Precedence
AF13 (14)
AF23 (22)
AF33 (30)
AF43 (38)
