832
C
HAPTER
76: DNS C
ONFIGURATION
Figure 213
Dynamic DNS resolution
Figure 213 shows the relationship between the user program, DNS Client and DNS
Server.
The resolver and cache compose the DNS Client. The user program runs on the
same machine as the DNS client, while the DNS Server and the DNS Client must
run on different machines.
Dynamic DNS resolution allows the DNS Client to store the latest name-to-address
mappings in the dynamic domain name cache. So there is no need to send a
request to the DNS Server for the same domain next time. The DNS Client removes
aged mappings from the cache, so as to obtain updated mappings from the DNS
Server. The setting on the DNS Server determines the aging time, and the DNS
Client gets the information from DNS messages.
DNS suffix list
The DNS Client normally holds a DNS suffix list where you can define some
domain name suffixes. It is used when the name to be resolved is not complete.
The resolver can use the list to supply the missing part. For example, you can
configure a suffix “com” in the list, and users only need to input “aabbcc” to get
the IP address of aabbcc.com, for the resolver will automatically add the suffix and
delimiter before passing the name to the DNS Server.
When a user input a domain name:
■
If there is no dot in the domain name, such as “aabbcc”, the resolver will
consider this as a host name and add a suffix to the name before performing
DNS lookup. If all the suffixes in the DNS suffix list have been tried but no DNS
lookup succeeds, the resolver will use the original name (such as aabbcc) for a
DNS lookup.
■
If there is a dot in the domain name, such as “www.aabbcc” or “aabbcc.”, the
resolver will first use this domain name to perform DNS lookup before trying
any other suffix.
Currently, the Switch 7750 Ethernet switches support both static and dynamic
domain name resolution on the DNS Client.
n
If you have configured aliases for domain names on the DNS server, the Ethernet
switch can resolve a host IP address according to its alias.
Request
Response
Response
Request
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DNS client
DNS server
Resolver
Cache
User
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Summary of Contents for Switch 7754
Page 32: ...32 CHAPTER 1 CLI OVERVIEW ...
Page 70: ...70 CHAPTER 5 LOGGING IN USING MODEM ...
Page 76: ...76 CHAPTER 7 LOGGING IN THROUGH NMS ...
Page 86: ...86 CHAPTER 9 CONFIGURATION FILE MANAGEMENT ...
Page 120: ...120 CHAPTER 13 ISOLATE USER VLAN CONFIGURATION ...
Page 126: ...126 CHAPTER 14 SUPER VLAN ...
Page 136: ...136 CHAPTER 16 IP PERFORMANCE CONFIGURATION ...
Page 152: ...152 CHAPTER 17 IPX CONFIGURATION ...
Page 164: ...164 CHAPTER 19 QINQ CONFIGURATION ...
Page 172: ...172 CHAPTER 21 SHARED VLAN CONFIGURATION ...
Page 182: ...182 CHAPTER 22 PORT BASIC CONFIGURATION ...
Page 198: ...198 CHAPTER 24 PORT ISOLATION CONFIGURATION ...
Page 208: ...208 CHAPTER 25 PORT SECURITY CONFIGURATION ...
Page 224: ...224 CHAPTER 27 DLDP CONFIGURATION ...
Page 232: ...232 CHAPTER 28 MAC ADDRESS TABLE MANAGEMENT ...
Page 240: ...240 CHAPTER 29 CENTRALIZED MAC ADDRESS AUTHENTICATION CONFIGURATION ...
Page 280: ...280 CHAPTER 30 MSTP CONFIGURATION ...
Page 348: ...348 CHAPTER 35 IS IS CONFIGURATION ...
Page 408: ...408 CHAPTER 39 802 1X CONFIGURATION ...
Page 412: ...412 CHAPTER 40 HABP CONFIGURATION ...
Page 422: ...422 CHAPTER 41 MULTICAST OVERVIEW ...
Page 426: ...426 CHAPTER 42 GMRP CONFIGURATION ...
Page 480: ...480 CHAPTER 47 PIM CONFIGURATION ...
Page 506: ...506 CHAPTER 48 MSDP CONFIGURATION ...
Page 552: ...552 CHAPTER 51 TRAFFIC ACCOUNTING CONFIGURATION ...
Page 570: ...570 CHAPTER 53 HA CONFIGURATION ...
Page 582: ...582 CHAPTER 54 ARP CONFIGURATION SwitchA arp protective down recover interval 200 ...
Page 622: ...622 CHAPTER 58 DHCP RELAY AGENT CONFIGURATION ...
Page 684: ...684 CHAPTER 61 QOS CONFIGURATION ...
Page 718: ...718 CHAPTER 63 CLUSTER ...
Page 738: ...738 CHAPTER 67 UDP HELPER CONFIGURATION ...
Page 752: ...752 CHAPTER 69 RMON CONFIGURATION ...
Page 772: ...772 CHAPTER 70 NTP CONFIGURATION ...
Page 796: ...796 CHAPTER 72 FILE SYSTEM MANAGEMENT ...
Page 802: ...802 CHAPTER 73 BIMS CONFIGURATION ...
Page 814: ...814 CHAPTER 74 FTP AND TFTP CONFIGURATION ...
Page 830: ...830 CHAPTER 75 INFORMATION CENTER ...
Page 836: ...836 CHAPTER 76 DNS CONFIGURATION ...
Page 852: ...852 CHAPTER 77 BOOTROM AND HOST SOFTWARE LOADING ...
Page 858: ...858 CHAPTER 78 BASIC SYSTEM CONFIGURATION DEBUGGING ...