nginx.conf

server {
 listen 80;
 resolver 4.2.2.2;
 location /folder1 {
  proxy_pass http://server1.domain.com:80;
 }
 
 location /folder2 {
  proxy_pass http://server2.domain.com:80;
 }
 
 location /folder3 {
  proxy_pass http://server3.domain.com:80;
 }
 
 location / {
  proxy_pass http://serverdefault.domain.com:80;
 }
}