Configuration Guide# DHCP Configuration: Router on a Stick (ROAS) Setup

Product: NGAF

Version: 8.0.47

1. Introduction

1.1 Scenario

In a small Enterprise Network, the network design is a Router-on-a-Stick (ROAS) setup in which the different VLANs can pass through a single connection.

Configure the Sangfor NGAF as the DHCP Server and provide IPv4 addresses on all the endpoints on the network in a ROAS setup.

1.2 Other Details

1) The VLANs (Virtual LANs) are VLAN10 (172.16.10.0/ 24) and VLAN20 (172.16.20.0/ 24).

2) The Core Switch port that is directly connected to the Sangfor NGAF is configured as a trunk port

3) Desktops’ IPs are assigned dynamically.

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2. Configuration Guide

2.1 NGAF Configuration

Step 1. Choose the interface eth1 and create Subinterface for VLAN 10 and 20.

Go to Network > Interfaces >Subinterfaces and click Add, as shown below:

Step 2. A new window will pop up when you click the Add Button. Then put the following details:

Physical Interfaces: eth1

1) VLAN ID: 10

2) Description: Sub-interface for VLAN10

3) Static IP: 172.16.10.1/255.255.255.0

Then click Save.

Step 3. Repeat Step 2 for VLAN 20.

1) Physical Interfaces: eth1

2) VLAN ID: 20

3) Description: Sub-interface for VLAN10

4) Static IP: 172.16.20.1/255.255.255.0

Then click Save.

Step 4. Configure the subinterface (eth1.10) for DHCP.

Go to Network > DHCP > DHCP Options and click Add, and put the following details as shown below:

1) Service Type: DHCP Server

2) Name: DHCP_Vlan10

3) Description: DHCP for Vlan10

4) Interface: eth1.10

5) IP Range: 172.16.10.100-172.16.10.254

6) Netmask: 255.255.255.0

7) DHCP Gateway: 172.16.10.1

8) DNS Server: Specified

9) Preferred DNS: 8.8.8.8

Then click Save

Step 5. Configure the subinterface (eth1.20) for DHCP

Go to Network > DHCP > DHCP Options and click Add, and put the following details as shown below:

1) Service Type: DHCP Server

2) Name: DHCP_Vlan20

3) Description: DHCP for Vlan20

4) Interface: eth1.20

5) IP Range: 172.16.20.100-172.16.20.254

6) Netmask: 255.255.255.0

7) DHCP Gateway: 172.16.20.1

8) DNS Server: Specified

9) Preferred DNS: 8.8.8.8

Then click Save.

Step 6. Verify the 2 DHCP Poll added as shown below:

Step 7. Verify if the devices can get dynamic IP Addresses by issuing the ipconfig/all at the cmd.

PC1

PC2

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3. Precaution

1). Always verify the VLAN configuration if the endpoint can’t get the right IP Address.

2). DHCP in ROAS is a real-world scenario but its single line makes it subject to failure. I suggest to have another line for redundancy.

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Hello, thanks for sharing. Can you share what will be the configuration of STATIC ROUTES, should I still add the IP Sub netmask of  VLAN 10 & VLAN 20? Thanks in advance.