HP VPN Firewall Appliances Network Management Configuration Guide

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Figure 128 DNS proxy networking application
A DNS proxy operates as follows:
1. A DNS client considers the DNS proxy as the DNS server, and sends a DNS request to the DNS
proxy. The destination address of the request is the IP address of the DNS proxy.
2. The DNS proxy searches the local static domain name resolution table and dynamic domain name
resolution table after receiving the request. If the requested information is found, the DNS proxy
returns a DNS reply to the client.
3. If the requested information is not found, the DNS proxy sends the request to the designated DNS
server for domain name resolution.
4. After receiving a reply from the DNS server, the DNS proxy records the IP address-to-domain name
mapping and forwards the reply to the DNS client.
With no DNS server or route to a DNS server specified, the DNS proxy does not forward DNS requests,
or answer requests from the DNS clients.
DNS spoofing
Figure 129 DNS spoofing application
DNS spoofing is applied to the dial-up network, as shown in Figure 129.
• The device connects to the PSTN/ISDN network through a dial-up interface and triggers the
establishment of a dial-up connection only when packets are to be forwarded through the dial-up
interface.