resolver 和 nslookup 的不同

resolv.conf中若配置一条name server记录，二者表现相同。若配置多条记录：
The resolver tries the first nameserver, then the second, then the first, then the second, until it receives a response or gives up. The resolver does this for every query. On the other hand, nslookup tries the first nameserver in resolv.conf and keeps retrying until it finally gives up on the first nameserver and tries the second. Once it gets a response, it locks onto that server and doesn't try the next.