CLI: Example for Configuring Multi-server Smart DNS in ISP Egress Mode

This section provides an example for configuring multi-server smart DNS in ISP egress mode.

Networking Requirements

As shown in Figure 1, an enterprise deploys two web servers to provide the web service whose domain name is www.example.com. The private IP address of ISP1 server is 10.1.1.10, and the public IP address after server mapping is 1.1.1.10. The private IP address of ISP2 server is 10.2.2.10, and the public IP address after server mapping is 2.2.2.10. The DNS server of on the intranet of the enterprise has the mappings between domain name www.example.com and the two server addresses (1.1.1.10 and 2.2.2.10).

An ISP1 user who accesses www.example.com obtains ISP1 server address 1.1.1.10 and accesses ISP1 server through ISP1 network. An ISP2 user who accesses www.example.com obtains ISP2 server address 2.2.2.10 and accesses ISP2 server through ISP2 network.

Figure 1 ISP egress-based multi-server smart DNS networking

Configuration Roadmap

As shown in Figure 1, ISP users usually obtain ISP server addresses 1.1.1.10 and 2.2.2.10. To enable ISP1 users to obtain ISP1 server address and ISP2 users to obtain ISP2 server address, configure smart DNS in ISP egress mode. The configuration roadmap is as follows:

Enable smart DNS.
Because two web servers are deployed on the intranet, configure multi-server smart DNS in ISP egress mode. Multi-server smart DNS needs to associate the ISP egresses and public ISP server addresses. For example, associate GE0/0/1 of ISP1 network with public ISP1 server address 1.1.1.10 and GE0/0/2 of ISP2 network with public ISP2 server address 2.2.2.10.
Configure the NAT server function.
- Configure NAT Server for ISP1 address 1.1.1.10 so that the FW can map 1.1.1.10 to 10.1.1.10 for ISP1 users to access ISP1 server.
- Configure NAT Server for ISP2 address 2.2.2.10 so that the FW can map 2.2.2.10 to 10.2.2.10 for ISP2 users to access ISP2 server.
Configure the sticky load balancing function.

Procedure

Enable smart DNS.
```
<FW> system-view
[FW] dns-smart enable
```
Create a smart DNS group and configure smart DNS mappings in the group view.
1. Create smart DNS group 1.
```
[FW] dns-smart group 1 type multi
```
2. Configure a smart DNS mapping to map the server address to be sent to ISP1 users to 1.1.1.10.
```
[FW-dns-smart-group-1] out-interface GigabitEthernet0/0/1 map 1.1.1.10
```
3. Configure a smart DNS mapping to map the server address to be sent to ISP2 users to 2.2.2.10.
```
[FW-dns-smart-group-1] out-interface GigabitEthernet0/0/2 map 2.2.2.10
```
4. Exit from the smart DNS group view.
```
[FW-dns-smart-group-1] quit
```
Configure the NAT server function.
1. Configure NAT Server for ISP1 address 1.1.1.10 so that the FW can map 1.1.1.10 to 10.1.1.10 for ISP1 users to access ISP1 server.
```
[FW] nat server isp1_server_nat global 1.1.1.10 inside 10.1.1.10 no-reverse
```
2. Configure NAT Server for ISP2 address 2.2.2.10 so that the FW can map 2.2.2.10 to 10.2.2.10 for ISP2 users to access ISP2 server.
```
[FW] nat server isp2_server_nat global 2.2.2.10 inside 10.2.2.10 no-reverse
```

Configure the sticky load balancing function.

[FW] interface GigabitEthernet0/0/1
[FW-GigabitEthernet0/0/1] ip address 1.1.1.2 24
[FW-GigabitEthernet0/0/1] gateway 1.1.1.1
[FW-GigabitEthernet0/0/1] redirect-reverse next-hop 1.1.1.1
[FW-GigabitEthernet0/0/1] quit
[FW] interface GigabitEthernet0/0/2
[FW-GigabitEthernet0/0/2] ip address 2.2.2.2 24
[FW-GigabitEthernet0/0/2] gateway 2.2.2.1
[FW-GigabitEthernet0/0/2] redirect-reverse next-hop 2.2.2.1
[FW-GigabitEthernet0/0/2] quit

Configuration Scripts

#
 nat server isp1_server_nat global 1.1.1.10 inside 10.1.1.10 no-reverse
 nat server isp2_server_nat global 2.2.2.10 inside 10.2.2.10 no-reverse
#
 dns-smart enable
#
dns-smart group 1 type multi
 out-interface GigabitEthernet0/0/1 map 1.1.1.10
 out-interface GigabitEthernet0/0/2 map 2.2.2.10
#
interface GigabitEthernet0/0/1
 ip address 1.1.1.2 255.255.255.0
 redirect-reverse next-hop 1.1.1.1
 gateway 1.1.1.1
#
interface GigabitEthernet0/0/2
 ip address 2.2.2.2 255.255.255.0
 redirect-reverse next-hop 2.2.2.1
 gateway 2.2.2.1