Sun. Aug 14th, 2022

The Quick Definition: Policy-based Routing (PBR) refers to a technique that uses routing decisions based upon policies established by network administrators.
What is Policy Routing?
Networks have become more complex due to factors like the cloud, mobility and web-based apps. These networks also have more voice and video data. This has led to an increase in the need to prioritize and separate traffic on our networks.
Policy-based routing allows for almost unlimited customization of routing patterns. The administrator simply identifies the type of traffic (web or VoIP, FTP, etc.). The administrator then determines the routing pattern for that traffic.
You can customize even to times of the day, IP subnets and any other variation with the simple, adaptable process described here. Let’s look at how to configure policy-based routing on Cisco routers.
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We will use this example to show you how to route the IT department in our hypothetical company to the fast connection and all other traffic to go to the slow connection.
Serial 0/0 will represent the fast connection, while serial 0/1 will represent the slow connection. VLAN 1 is where the IT department is located, at 10.1.0.0/16. All traffic to other subnets is on 10.2.0.0. The goal is to direct traffic to the first group to serial 1/1 using policy-based routing.
How to create the Access List
First, create an access list. This will allow you to filter traffic through your network. You can then open the router console and bring up the configuration using conf t. This will prompt you to enter configuration commands.
Enter:
access-list 50 permit 10.1.0.0 0.0.255.255
The number 50 immediately after the ‘access-list” command indicates that this is a Standard access list. The permit string identifies the source of traffic. This access list will serve as the reference point for the route map when determining the type traffic subject to established routing protocols.
Start the Route Map
Next, create a route map that will separate the traffic. Enter the POLICY command route-map. This POLICY entry simply names the route map to reflect its purpose. Our Route Map will be called “IT-Fast.”
A route map is a sequence of if-then statements which request inputs and then feed them to predetermined outputs. These if-then commands can be represented in the router console by match and set
Configuring the Route Map
Match input is the if statement entry and the first entry to the route map. Enter match ip adres 50. This will establish the input to the access list 50 10.1 subnets, identifying the IT department. Next, set will determine where the subgroup will be routed.
The ideal scenario is that traffic will be routed towards the IP address of the fast connection gateway service provider. In this case, we haven’t established such an address so we will instead use the interface configuration.
Enter set interface serial 0. The traffic from the access list will now be directed to serial0/0. This was previously established to represent the fast connection.
Router(config)# route-map IT-FastRouter(config-route-map)# match ip address 50Router(config-route-map)# set interface serial0/0
Sequencing the Route Map
We didn’t assign a number to the first sequence of route maps, so it defaulted at 10. To indicate the next step in the route map, enter “routemap IT-Fast 20” at the route-map POLICY prompt. Traffic will not stop if it is not moving.

By Adam