Chapter 6 Configuration Basics

Packet Flow The packet flow is as follows:

•Automatic SNAT and WAN trunk routing for traffic going from internal to external interfaces (you don’t need to configure anything to all LAN to WAN traffic).

The ZyWALL automatically adds all of the external interfaces to the default WAN trunk. External interfaces include ppp and cellular interfaces as well as any Ethernet interfaces that are set as external interfaces.

Examples of internal interfaces are any Ethernet interfaces that you configure as internal interfaces.

•A policy route can be automatically disabled if the next-hop is dead.

•You do not need to set up policy routes for IPSec traffic.

•Policy routes can override direct routes.

•You do not need to set up policy routes for 1:1 NAT entries.

•You can create Many 1:1 NAT entries to translate a range of private network addresses to a range of public IP addresses

•Static and dynamic routes have their own category.

6.4.1Routing Table Checking Flow

When the ZyWALL receives packets it defragments them and applies destination NAT. Then it examines the packets and determines how to route them. The checking flow is from top to bottom. As soon as the packets match an entry in one

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ZyWALL USG 50 User’s Guide