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Using NAT with other features
VRF-aware NAT
VRF-aware NAT allows users from different VRF (VPN instances) to access external networks and
to access each other.
1. Upon receiving a request from a user in a VRF to an external network, NAT performs the
following tasks:
{ Translates the private source IP address and port number to a public IP address and port
number.
{ Records the VRF information, such as the VRF name.
2. When a response packet arrives, NAT performs the following tasks:
{ Translates the destination public IP address and port number to the private IP address and
port number.
{ Forwards the packet to the target VRF.
NAT with DNS mapping
NAT with DNS mapping allows an internal host to access an internal server on the same private
network by using the domain name of the internal server when the DNS server is on the public
network.
NAT with DNS mapping must operate with the NAT Server feature.
Figure 63 NAT with DNS mapping
As shown in Figure 63, NAT with DNS mapping works as follows:
1. The host sends a DNS request containing the domain name of the internal Web server.
2. Upon receiving the DNS response, the NAT device performs a DNS mapping lookup by using
the domain name in the response. A DNS mapping for NAT maps the domain name to the
public IP address, public port number, and the protocol type for the internal server.
3. If a match is found, the NAT continues to compare the public address, public port number, and
the protocol type with the NAT Server configuration. The NAT Server configuration maps the
public IP address and port number to the private IP address and port number for the internal
server.
4. If a match is found, NAT translates the public IP address in the response into the private IP
address of the Web server.
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