Chapter 51 System
ZyWALL / USG (ZLD) CLI Reference Guide
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51.6 DNS Overview
DNS (Domain Name System) is for mapping a domain name to its corresponding IP address and
vice versa. The DNS server is extremely important because without it, you must know the IP
address of a machine before you can access it.
51.6.1 Domain Zone Forwarder
A domain zone forwarder contains a DNS server’s IP address. The ZyWALL / USG can query the
DNS server to resolve domain zones for features like VPN, DDNS and the time server. A domain
zone is a fully qualified domain name without the host. For example, zyxel.com.tw is the domain
zone for the www.zyxel.com.tw fully qualified domain name.
A name query begins at a client computer and is passed to a resolver, a DNS client service, for
resolution. The ZyWALL / USG can be a DNS client service. The ZyWALL / USG can resolve a DNS
query locally using cached Resource Records (RR) obtained from a previous query (and kept for a
period of time). If the ZyWALL / USG does not have the requested information, it can forward the
request to DNS servers. This is known as recursion.
The ZyWALL / USG can ask a DNS server to use recursion to resolve its DNS client requests. If
recursion on the ZyWALL / USG or a DNS server is disabled, they cannot forward DNS requests for
resolution.
A Domain Name Server (DNS) amplification attack is a kind of Distributed Denial of Service (DDoS)
attack that uses publicly accessible open DNS servers to flood a victim with DNS response traffic.
An open DNS server is a DNS server which is willing to resolve recursive DNS queries from anyone
on the Internet.
In a DNS amplification attack, an attacker sends a DNS name lookup request to an open DNS
server with the source address spoofed as the victim’s address. When the DNS server sends the
DNS record response, it is sent to the victim. Attackers can request as much information as possible
to maximize the amplification effect.
Содержание ZyWALL USG Series
Страница 19: ...19 PART I Introduction ...
Страница 20: ...20 ...
Страница 38: ...Chapter 2 User and Privilege Modes ZyWALL USG ZLD CLI Reference Guide 38 ...
Страница 39: ...39 PART II Reference ...
Страница 40: ...40 ...
Страница 48: ...Chapter 4 Status ZyWALL USG ZLD CLI Reference Guide 48 ...
Страница 52: ...Chapter 5 Registration ZyWALL USG ZLD CLI Reference Guide 52 ...
Страница 128: ...Chapter 15 Route ZyWALL USG ZLD CLI Reference Guide 128 ...
Страница 136: ...Chapter 17 Zones ZyWALL USG ZLD CLI Reference Guide 136 ...
Страница 140: ...Chapter 18 DDNS ZyWALL USG ZLD CLI Reference Guide 140 ...
Страница 148: ...Chapter 20 HTTP Redirect ZyWALL USG ZLD CLI Reference Guide 148 ...
Страница 152: ...Chapter 21 ALG ZyWALL USG ZLD CLI Reference Guide 152 ...
Страница 156: ...Chapter 22 UPnP ZyWALL USG ZLD CLI Reference Guide 156 ...
Страница 159: ...Chapter 23 IP MAC Binding ZyWALL USG ZLD CLI Reference Guide 159 ...
Страница 178: ...Chapter 25 Secure Policy ZyWALL USG ZLD CLI Reference Guide 178 ...
Страница 218: ...Chapter 32 Application Patrol ZyWALL USG ZLD CLI Reference Guide 218 ...
Страница 236: ...Chapter 34 IDP Commands ZyWALL USG ZLD CLI Reference Guide 236 ...
Страница 246: ...Chapter 35 Content Filtering ZyWALL USG ZLD CLI Reference Guide 246 ...
Страница 256: ...Chapter 36 Anti Spam ZyWALL USG ZLD CLI Reference Guide 256 ...
Страница 262: ...Chapter 37 SSL Inspection ZyWALL USG ZLD CLI Reference Guide 262 ...
Страница 268: ...Chapter 38 Device HA ZyWALL USG ZLD CLI Reference Guide 268 ...
Страница 284: ...Chapter 41 Addresses ZyWALL USG ZLD CLI Reference Guide 284 ...
Страница 288: ...Chapter 42 Services ZyWALL USG ZLD CLI Reference Guide 288 ...
Страница 302: ...Chapter 46 Authentication Server ZyWALL USG ZLD CLI Reference Guide 302 ...
Страница 338: ...Chapter 52 System Remote Management ZyWALL USG ZLD CLI Reference Guide 338 ...
Страница 358: ...Chapter 53 File Manager ZyWALL USG ZLD CLI Reference Guide 358 ...
Страница 372: ...Chapter 56 Session Timeout ZyWALL USG ZLD CLI Reference Guide 372 ...
Страница 374: ...Chapter 57 Diagnostics ZyWALL USG ZLD CLI Reference Guide 374 ...
Страница 384: ...Chapter 59 Maintenance Tools ZyWALL USG ZLD CLI Reference Guide 384 ...
Страница 426: ...List of Commands Alphabetical ZyWALL USG ZLD CLI Reference Guide 426 ...