ZyXEL Communications 200 Series 用户手册

Chapter 31 Content Filtering

ZyWALL USG 100/200 Series User’s Guide

This section provides content filtering background information.

The content filter lookup process is described below. 

Figure 411   Content Filter Lookup Procedure

1 A computer behind the ZyWALL tries to access a web site.
2 The ZyWALL looks up the web site in its cache. If an attempt to access the web site was 

made in the past, a record of that web site’s category will be in the ZyWALL’s cache. 
The ZyWALL blocks, blocks and logs or just logs the request based on your 
configuration. 

Category

This field shows whether access to the web site’s URL was blocked or allowed.
Click the column heading to sort the entries. Point the triangle up to display the 
blocked URLs before the URLs to which access was allowed.  Point the triangle 
down to display the URLs to which access was allowed before the blocked URLs. 

URL

This is a web site’s address that the ZyWALL previously checked with the external 
content filtering database.

Remaining Time 
(minutes)

This is the number of minutes left before the URL entry is discarded from the 
cache.

Remove

Click the Delete icon to remove the URL entry from the cache.

URL Cache Setup

Maximum TTL

Type the maximum time to live (TTL) (1 to 720 hours). This sets how long the 
ZyWALL is to keep an entry in the URL cache before discarding it.
The external content filtering database frequently adds previously uncategorized 
web sites and sometimes changes a web site’s category. Setting this limit higher 
will speed up the processing of web access requests but will also make it take 
longer for the ZyWALL to reflect changes in the external content filtering database.

Apply

Click Apply to save your changes back to the ZyWALL.

Reset

Click Reset to begin configuring this screen afresh.

Table 176   Anti-X > Content Filter > Cache (continued)