Netgear XSM4324FS Software Administration Manual Software Version 12.x - Page 155

M4300 Series and M4300-96X Fully Managed Switches Policy-Based Routing Concepts Normally, switches make forwarding decisions based on routing tables, which get populated by information given by dynamic routing protocols or static routing, to forward packets to destination addresses. Policy-based routing (PBR) is a feature that enables network administrators to define forwarding behavior based on packet contents. PBR is used to override traditional destination-based routing behavior. Configuring PBR involves configuring a route map with the match and set commands and then applying the corresponding route map to the inbound traffic on routing interfaces. One interface can contain only one route-map tag, but administrators can create multiple route-map entries with different sequence numbers. These entries are evaluated in sequence-number order until the first match is found. If no match is found, packets are routed as usual. Route-Map Statements A route-map statement that is used for PBR is configured as permit or deny. If the statement is marked as deny, traditional destination-based routing is performed on the packet that meet the match criteria: • If users specify any match/set statements in a route-map statement that are marked as deny, they will not be effective because traditional destination-based routing is performed on packets meeting the specified match criteria. • If the statement is marked as permit, and if the packet meets all the match criteria, then the set commands in the route-map statement are applied. If no match is found in the route map, the packet is not dropped. Packets are forwarded using the routing decision that is made by performing destination-based routing. If network administrators do not want to revert to normal forwarding, but instead want to drop a packet that does not match the specified criteria, a set statement needs to be configured to route the packets to interface null 0 as the last entry in the route map. Packets that are generated by the switch itself are not normally policy routed. But a provision in other industry standard products applies a policy through a local PBR. All packets originating on the switch are then subject to the local PBR. However, this feature is not supported. Starting with Software Version 10.2, the NETGEAR switch supports the route-map infrastructure for BGP. Match parameters defined in this chapter for policy-based routing operate in isolation with BGP. These options do not interfere with BGP protocol processing or policy propagation in any way. For example, if a match clause is placed in a route-map statement based on the length of the packet, BGP does not honor that clause. As stated earlier, these statements apply for L3 routed traffic (mainly data traffic) to override a routing decision. PBR 155 Software Administration Manual