Chapter 8 Route

8.2.1 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.

Table 45 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)

 

 

 

 

 

8.2.2 Policy Route Command Example

The following commands create two address objects (TW_SUBNET and GW_1) and insert a policy that routes the packets (with the source IP address TW_SUBNET and any destination IP address) through the interface ge1 to the next-hop router GW_1. This route uses the IP address of the outgoing interface as the matched packets’ source IP address.

Router(config)# address-object TW_SUBNET 192.168.2.0 255.255.255.0 Router(config)# address-object GW_1 192.168.2.250 Router(config)# policy insert 1

Router(policy-route)# description example Router(policy-route)# destination any Router(policy-route)# interface ge1 Router(policy-route)# next-hop gateway GW_1 Router(policy-route)# snat outgoing-interface Router(policy-route)# source TW_SUBNET Router(policy-route)# exit Router(config)# show policy-route 1

index: 1 active: yes description: example user: any schedule: none interface: ge1 tunnel: none sslvpn: none source: TW_SUBNET destination: any DSCP code: any service: any nexthop type: Gateway nexthop: GW_1

nexthop state: Not support

auto destination: no

bandwidth: 0

bandwidth priority: 0

maximize bandwidth usage: no

SNAT: outgoing-interface

DSCP marking: preserve

amount of port trigger: 0 Router(config)#

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ZyWALL (ZLD) CLI Reference Guide