Chapter 16: Dynamic Routing Protocols
STANDARD Revision 1.0
C4® CMTS Release 8.3 User Guide
© 2016 ARRIS Enterprises LLC. All Rights Reserved.
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Policy-Based Routing (PBR)
IP packets are normally directed by routing protocols and route tables, which make forwarding decisions based on the
destination IP addresses of packets. Policy-based Routing (PBR) enables network engineers to create policies for packets
with matching criteria, causing them to take paths that differ from the next-hop path specified by the route table. To
enable PBR, the user must configure a route map and apply it to an interface. PBR is then applied to all incoming packets
arriving at that interface.
The principal benefits of PBR include the following:
Forwarding is based not on destination IP address but on packet attributes such as source IP or packet type.
Route maps can improve service by enforcing Quality of Service (QOS) sorting at the edge router.
Cost-savings can be achieved by segregating slow bulky traffic from time-sensitive traffic.
Traffic can be separated according to desired characteristics and load balanced across multiple and unequal paths.
Note: The route maps used by the BGP routing protocol are part of a separate feature and are not affected by commands
to create or configure policy-based route maps.
Configuring PBR
Configuring PBR involves creating a route map with match and set commands and then applying the route map to an
interface.
Route Map Statements
Route map statements can result in a permit or deny action on matching packets
Deny means that normal destination-based routing will be used to forward the packet;
Permit means that some set command will be used to route the packet.
Route maps are given unique names (map-tags in CLI) and can have up to ten statements. Each statement is assigned a
sequence number. Because the C4/c CMTS supports a maximum of 2,048 route map statements, if each route map
contains a maximum of ten statements, the C4/c CMTS could support a maximum of 204 route maps.
Types of PBR commands: