ZyXEL ZyWALL ATP700 User Guide - Page 336
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Chapter 10 Routing 10.1.2 What You Need to Know Policy Routing Traditionally, routing is based on the destination address only and the Zyxel Device takes the shortest path to forward a packet. IP Policy Routing (IPPR) provides a mechanism to override the default routing behavior and alter the packet forwarding based on the policy defined by the network administrator. Policy-based routing is applied to incoming packets on a per interface basis, prior to the normal routing. How You Can Use Policy Routing • Source-Based Routing - Network administrators can use policy-based routing to direct traffic from different users through different connections. • Bandwidth Shaping - You can allocate bandwidth to traffic that matches routing policies and prioritize traffic (however the application patrol's bandwidth management is more flexible and recommended for TCP and UDP traffic). You can also use policy routes to manage other types of traffic (like ICMP traffic) and send traffic through VPN tunnels. Note: Bandwidth management in policy routes has priority over application patrol bandwidth management. • Cost Savings - IPPR allows organizations to distribute interactive traffic on high-bandwidth, high-cost paths while using low-cost paths for batch traffic. • Load Sharing - Network administrators can use IPPR to distribute traffic among multiple paths. • NAT - The Zyxel Device performs NAT by default for traffic going to or from the WAN interfaces. A routing policy's SNAT allows network administrators to have traffic received on a specified interface use a specified IP address as the source IP address. Note: The Zyxel Device automatically uses SNAT for traffic it routes from internal interfaces to external interfaces. For example LAN to WAN traffic. Static Routes The Zyxel Device usually uses the default gateway to route outbound traffic from computers on the LAN to the Internet. To have the Zyxel Device send data to devices not reachable through the default gateway, use static routes. Configure static routes if you need to use RIP or OSPF to propagate the routing information to other routers. See Chapter 10 on page 346 for more on RIP and OSPF. Policy Routes Versus Static Routes • Policy routes are more flexible than static routes. You can select more criteria for the traffic to match and can also use schedules, NAT, and bandwidth management. • Policy routes are only used within the Zyxel Device itself. Static routes can be propagated to other routers using RIP or OSPF. • Policy routes take priority over static routes. If you need to use a routing policy on the Zyxel Device and propagate it to other routers, you could configure a policy route and an equivalent static route. DiffServ QoS is used to prioritize source-to-destination traffic flows. All packets in the same flow are given the same priority. CoS (class of service) is a way of managing traffic in a network by grouping similar types of ZyWALL ATP Series User's Guide 336