2. May be a dialup machine has very slow internet connection where resolving a DNS query might take more time.
The solution for both the problems is to have a caching DNS server. Installing a dnsmasq and running it as a service on local host will resolve the issue.
Steps to Setup DNS Cache Server
(Following lines works good in Fedora / Redhat / CentOS)
Install dnsmasq
$ yum install dnsmasq
Make dnsmasq start on boot
$ chkconfig dnsmasq on
Start dnsmasq immediately
$ service dnsmasq start
Change the network setting to work through this cache server
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Open the network settings
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Move the primary and secondary to secondary and tertiary.
Click File->Save
Restart the network
$ service network restart
Test the network DNS resolving speed after the first time access to the site. It will be much faster as it comes from local.