Configuring Nat; Establishing The Configuration Task - Huawei quidway s7700 Configuration Manual

Quidway S7700 Smart Routing Switch
Configuration Guide - SPU
Temporary address = Start IP address in the temporary address pool + (Overlapped IP address
- Start IP address in the overlapped address pool)
Overlapped address = Start IP address in the overlapped address pool + (Temporary IP address
- Start IP address in the temporary address pool)
When PC2 on the private network accesses PC3 on the public network through the domain name,
the packet is processed as follows:
1.
2.
3.
4.
Source Address Associated with the VPN Before NAT Is Performed
The SPU enabled with NAT allows users on private networks to access the public network and
users of different VPNs to access the public network through the same egress. In addition, users
in the VPNs with the same IP address can access the public network.
NAT Server Associated with the VPN
The SPU enabled with NAT supports association between the VPN and the NAT server and
allows users on the public network to access hosts in the VPN. It is applied to the scenario where
IP addresses of multiple VPNs are overlapped.

3.3 Configuring NAT

To implement communication between the private network and the public network through
NAT, you can use Easy IP for a single user and the address pool for multiple users.

3.3.1 Establishing the Configuration Task

Before configuring NAT, familiarize yourself with the applicable environment, complete the
pre-configuration tasks, and obtain the required data.
Issue 01 (2011-07-15)
PC2 sends a DNS request for resolving the domain name being www.web.com of the Web
server. After the DNS server resolves the DNS request, the SPU receives the response
packet of the DNS server. The SPU resolves the address 10.0.0.1 in the payload of the
response packet and detects that the address is the overlapped address (it matches the
overlapped address pool). Then the SPU translates the address 10.0.0.1 to the temporary
address 3.0.0.1. The SPU translates the destination address of the response packet through
basic NAT and then sends it to PC2.
PC2 uses the temporary address 3.0.0.1 corresponding to www.web.com to access the
public network. When a packet reaches the SPU, the SPU translates the source address of
the packet through basic NAT and then translates the destination address (that is, temporary
address) of the packet to the overlapped address 10.0.0.1.
PC2 sends the packet to the outbound interface of the WAN. The packet is then forwarded
to PC3 hop by hop.
When the packet sent from PC3 to PC2 reaches the SPU, the SPU checks the source address
10.0.0.1, which is the overlapped address (it matches the overlapped address pool). Then
the SPU translates the source address to the temporary address 3.0.0.1. The SPU translates
the destination address of the response packet through basic NAT and then sends it to PC2.
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