Cant resolve site from internal LAN.

Question

Hi all, 
 I have a XG210 in gateway mode. Also I have a server with a site (100.100.100.4) in it and an internal DNS server (100.100.100.2) to publish the site. 
 I can see the site from the internet but not from the internal LAN. 
 I have a DNAT rule to also access the site from external sites. 
 I create a DNS host entry. 
 
 And I'm pretty sure no DNS traffic is blocked by the firewall. 
 Users have 8.8.8.8 and 4.2.2.2 as DNS in their machines, I did switch the DNS IP to our internal DNS and still can't resolve it. 
 I can ping the host 100.100.100.4 from the LAN. 
 I don't have DHCP configured in the XG. 
 Any help would be appreciated. 
 
 Thanks.

John Henry Vindas Carballo · Accepted Answer

UPDATE: 
 I'm able to resolve the site from the LAN after check the "Create Reflexive Rule" option in the DNAT rule of the site.

lferrara · Answer

John, 
 if you are using internal DNS, make sure to create a the proper record A inside the proper zone and that computers are able to resolve "www" by name. 
 Take note that "www" is not sufficient. In your internal network, computers are joined to a domain, for example test.local, so creating a www will correspond to www.test.local. 
 On XG, create the host using FQDN and ping the name from XG and check if it works. 
 Regards