Figure 149 Link Sticking - ZyXEL Communications ZyWALL USG 300 User Manual

Unified security gateway

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Table of Contents

Chapter 11 Trunks

• If that interface's connection goes down, the ZyWALL can still send its traffic through

another interface.

• You can define multiple trunks for the same physical interfaces.

Link Sticking

You can have the ZyWALL send each local computer's traffic through a single WAN

interface for a specified period of time. This is useful when a redirect server forwards a user

request for a file and informs the file server that a particular WAN IP address is requesting the

file. If the user's subsequent sessions came from a different WAN IP address, the file server

would deny the request. Here is an example.

Figure 149 Link Sticking

1 LAN user A tries to download a file from server B on the Internet. The ZyWALL uses

ge2 to send the request to server B.

2 However remote server B is actually a redirect server. So server B sends a file list to

LAN user A. The file list lets LAN user A's computer know that the desired file is

actually on file server (C). At the same time, register server B informs file server C that

a computer located at the ge2's IP address will download a file.

3 The ZyWALL is using active/active load balancing. So when LAN user A tries to

retrieve the file from file server C, the request goes out through ge3.

4 File server C finds that the request comes from ge3's IP address instead of ge2's IP

address and rejects the request.

5 If link sticking had been configured, the ZyWALL would have still used ge2 to send

LAN user A's request to file server C and the file server would have given the file to A.

Load Balancing Algorithms

The following sections describe the load balancing algorithms the ZyWALL can use to decide

which interface the traffic (from the LAN) should use for a session

you configure on the ZyWALL refers to the actual bandwidth provided by the ISP and the

measured bandwidth refers to the bandwidth an interface is currently using.

In the load balancing section, a session may refer to normal connection-oriented, UDP and SNMP2 traffic.

. The available bandwidth

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