Policy-Based Routing Configuration Guide

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Introduction

Policy-Based Routing (PBR) is a routing mechanism that forwards packets based on custom-defined policies. When packets are routed, they can be matched based on source IP address, destination IP address, IP protocol, source TCP/UDP port number, and destination TCP/UDP port number. For packets that meet the matching conditions, the next hop is set to complete the forwarding control of the packets.

Policy-Based Routing Configuration

Configure Policy-Based Routing

Table 1 Configure Policy-Based Routing

Purpose	Commands	Description
Enter global configuration view.	configure terminal	-
Create a PBR policy and enter the pbr-map configuration view	pbr-map pbr-map-name seq seq-num	sequence number, with a value range of 1 to 700.
Configure PBR policy matching fields	match {dst-ip dip\|dst-port dport\|ip-protocol {tcp\|udp}\|src-ip sip\|src-port sport}	-
Configure PBR policy actions	set {nexthop {A.B.C.D\|X:X::X:X}\|nexthop-group next-group-name}	-
Create a next-hop group and enter the next-hop group configuration view	nexthop-group next-group-name	-
Configure the next hop	nexthop {A.B.C.D\|X:X::X:X}	-

Configure interface binding with policy routing

Table 2 Configure interface binding with policy routing

Purpose	Commands	Description
Enter global configuration view	configure terminal	-
Enter interface configuration view.	interface interface-type interface-name	Interface type: optional ethernet, link-aggregation
Bind PBR policy	pbr-policy pbr-map-name	pbr-map-name: PBR policy name

Display and Maintenance

Table 3 PBR Display and Maintenance

Purpose	Command	Description
Check PBR binding information.	show pbr interface [ethernet interface-name\|link-aggregation lag-id] [json]	-
Check PBR policy information.	show pbr map [pbr-map-name\|json\|detail]	-
Check PBR next hop information.	show pbr nexthop-groups [next-group-name\|json]	-

Typical Configuration Example

Networking Requirements To achieve flexible scheduling and refined management of traffic, policy routing (PBR) technology needs to be deployed in the network architecture. We now require VM1 to serve as the traffic source, release two streams of traffic externally, configure PBR through the switch, and forward one stream to VM2 and the other stream to VM3 to meet the traffic processing needs in different business scenarios, improve network resource utilization efficiency and business flexibility.
Topology

Procedure

#Configure Interface IP.

sonic# config terminal
sonic(config)# interface ethernet 0/72
sonic(config-if-0/72)# ip address 72.0.0.1/24
sonic(config-if-0/72)# exit
sonic(config)# interface ethernet 0/73
sonic(config-if-0/73)# ip address 73.0.0.1/24
sonic(config-if-0/73)# exit
sonic(config)# interface ethernet 0/74
sonic(config-if-0/74)# ip address 74.0.0.1/24
sonic(config-if-0/74)# exit

#Configure PBR.

sonic# config terminal
sonic(config)# pbr-map test seq 1
sonic(config-pbr-map)# match src-ip 1.0.0.0/24
sonic(config-pbr-map)# set nexthop 73.0.0.2
sonic(config-pbr-map)# exit
sonic(config)# pbr-map test seq 2
sonic(config-pbr-map)# match src-ip 2.0.0.0/24
sonic(config-pbr-map)# set nexthop 74.0.0.2
sonic(config-pbr-map)# exit
sonic(config)# interface ethernet 0/72
sonic(config-if-0/72)# pbr-policy test
sonic(config-if-0/72)# exit

Verify the configuration.

#Check pbr configuration

sonic# show pbr interface
  ethernet 0/72(106) with pbr-policy test
Leaf-129# show pbr nexthop-groups
Nexthop-Group: test2 Table: 10001 Valid: 0 Installed: 0
        Valid: 0 nexthop 74.0.0.2
Nexthop-Group: test1 Table: 10000 Valid: 0 Installed: 0
        Valid: 0 nexthop 73.0.0.2
Leaf-129# show pbr map
  pbr-map test valid: no
    Seq: 1 rule: 300
        Installed: no Reason: Invalid NH
        SRC Match: 1.0.0.0/24
        nexthop 73.0.0.2
          Installed: no Tableid: 10000
    Seq: 2 rule: 301
        Installed: no Reason: Invalid NH
        SRC Match: 2.0.0.0/24
        nexthop 74.0.0.2
          Installed: no Tableid: 10001

TC2 is configured with HOST1 IP: 73.0.0.2, gateway IP: 73.0.0.1. TC3 is configured with HOST2 IP: 74.0.0.2, gateway IP: 74.0.0.1. TC1 sends two streams with source IPs 1.0.0.1 and 2.0.0.1, TC2 can capture the stream with source IP 1.0.0.1, and TC3 can capture the stream with source IP 2.0.0.1.