1-2Figure 1-1 Dynamic domain name resolutionFigure 1-1 shows the relationship between user program, DNS client, and DNS server.The resolver and cache comprise the DNS client. The user program and DNS client run on the samedevice, while the DNS server and the DNS client usually run on different devices.Dynamic domain name resolution allows the DNS client to store latest mappings between name and IPaddress in the dynamic domain name cache of the DNS client. There is no need to send a request to theDNS server for a repeated query request next time. The aged mappings are removed from the cacheafter some time, and latest entries are required from the DNS server. The DNS server decides how longa mapping is valid, and the DNS client gets the information from DNS messages.DNS suffixesThe DNS client normally holds a list of suffixes which can be defined by users. It is used when the nameto be resolved is not complete. The resolver can supply the missing part (automatic domain nameaddition). For example, a user can configure com as the suffix for aabbcc.com. The user only needs totype aabbcc to get the IP address of aabbcc.com. The resolver can add the suffix and delimiter beforepassing the name to the DNS server.z If there is no dot in the domain name, such as aabbcc, the resolver will consider this as a host nameand add a DNS suffix before processing. The original name such as aabbcc is used if all DNSlookups fail.z If there is a dot in the domain name, such as www.aabbcc or aabbcc., it indicates that no DNSsuffix needs to be added and the resolver will use this domain name to do DNS lookup first. If thelookup fails, the resolver adds a DNS suffix for another lookup.Configuring Domain Name ResolutionConfiguring Static Domain Name ResolutionTable 1-1 Configure static domain name resolutionOperation Command RemarksEnter system view system-view —Configure a mapping betweena host name and an IP address ip host hostname ip-addressRequiredNo IP address is assigned to ahost name by default.
