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

Open the network settings
Add the Primary DNS as localhost by adding 127.0.0.1Move 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.