Chapter 6 Tutorials

Figure 96 Create a Firewall Rule

6.7 NAT Loopback

The NAT 1:1 example in Section 6.6 on page 147 maps a public IP address to the private IP address of a LAN SMTP mail server to allow users to access the SMTP mail server from the WAN. LAN users can also use an IP address to access the mail server. However, you need to configure NAT loopback for LAN users to use a domain name to access the server.

Figure 97 LAN Computer Queries the DNS Server

DNS

xxx.LAN-SMTP.com = ? 1.1.1.1

LAN

xxx.LAN-SMTP.com = 1.1.1.1

192.168.1.21192.168.1.89

A LAN user computer at IP address 192.168.1.89 queries the domain name (xxx.LAN- SMTP.com in this example) from a public DNS server and gets the SMTP server’s 1-1 NAT mapped public IP address of 1.1.1.1.

 

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