Enterasys Networks X-PeditionTM manual Policy Based Routing, QoS with Vlan

IP Routing Protocols

Figure 5-7 WAN Interface to VLAN Ethernet Topology

				IP Routing Table
				1.2.3.0/24 F1.1
				3.3.2.0/24 Serial 1	VLAN 1200
	IP 3.2.3.4/24			9.9.9.0/24 Serial 1 (Static)
					IP 1.2.3.4/24
	PPP encapsulation			F1.1
					Ethernet		VLAN Tag		IP: 9.9.9.1
PPP		IP: 9.9.9.1
			Serial 1			3
Incoming Serial frame
	1				Priority	CFI		VLAN: 1200
					Outgoing VLAN tagged frame

For sample configurations, refer to “Configuring VLAN Examples” on page 5-46.

QoS with VLAN

The XSR’s support for Quality of Service (QoS) with VLAN is described in the chapter “Configuring Quality of Service” on page 12-1.

Policy Based Routing

IP packets typically are forwarded according to the route chosen by traditional routing protocols RIP, OSPF, BGP or static routes. Selection is based only on the destination of the packet. Policy Based Routing (PBR) allows you to selectively forward some patterned packets through alternative paths. It is not meant to replace routing protocols but is complementary while adding flexibility. If any packets do not meet policy criteria, the destination-based routing table will be searched.

PBR is beneficial for the following reasons:

•Flexible Transit Provider Selection - Internet service providers and others can set priorities for their customers and use PBR to route traffic according to their users' priorities through different Internet connections across policy routers.

•Cost Savings - PBR can cut networking costs by distributing traffic among low-cost and high- cost paths.

•Load Sharing - You can implement policies to distribute traffic among multiple paths based on traffic characteristics as opposed to traditional load sharing. With PBR, the same traffic flow will go through the same path but different traffic flow will be directed over a different path according to the policy.

Note: Policy-based routing takes precedence over destination-based routing.

Accessing the Global Routing Policy Table

Policy-based routing can be applied to incoming packets only and can be enabled on any interface with the ip policy command. It works as follows:

1.If a packet is a candidate for PBR, the XSR consults a global routing policy table in the form of a route-map table having multiple entries. Each entry is assigned a sequence number and are sequentially ordered from low to high. The route-map pbr command specifies the sequence number and acquires PBR configuration mode. You can display this information with the show route-map pbr command.

5-22 Configuring IP