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Configure DHCP over VPN in Cyberoam

Applicable Version: 10.00 onwards

Overview

Allocation of address space is one of the major challenges when planning and deploying a VPN network. With the ability to tunnel DHCP over VPNs, it allows network administrators to manage their entire IP address space from a central DHCP server. In addition, by enabling this feature, it will allow roaming users to travel across multiple branches and administrators can have control over the network. 

This article describes a detailed configuration example that demonstrates how to configure DHCP over Site-to-Site IPSec VPN tunnel between two Cyberoam.

Scenario

A hypothetical example has been shown where Head Office has a DHCP Server and IP addresses needs to be leased to Branch Office users connected over Site-to-Site VPN Tunnel.
 
 

 

 

Prerequisite

A Site-to-Site VPN Tunnel should be configured between Head office and Branch office. For details on how to configure an IPSec tunnel, refer to the following articles: 

 
Branch Office Configuration

You must be logged on to the Web Admin Console as an administrator with Read-Write permission for relevant feature(s).

Step 1: Configure Branch Office Cyberoam as DHCP Relay Agent

Go to Network > DHCP > Relay and click Add to create a relay agent as per parameters below. 

 

Parameters

Value

Description

Name

DHCPoverVPN

Provide a name to identify DHCP Relay Agent.

IP Family

IPv4

Select the IP Family for DHCP Relay Agent.

Interface

PortA - 172.16.1.1

Select internal interface.

 

DHCP Relay agent can be configured on virtual sub-interface but cannot be configured on Interface alias.

DHCP Server IP

172.16.1.5

Specify DHCP Server IP Address. You can also configure multiple DHCP servers. This support deployment where DHCP server running in high availability environment. DHCP Relay will forward packets to all the configured DHCP Servers and active server will serve the request. In case active server goes down, backup server serves the request. DHCP server takes care of leasing the IP Address to a client.

 

Maximum DHCP servers configures per DHCP Relay - 8

Relay through IPSec

(Only if IP Family is IPv4)

Enable

Click to enable Relay through IPSec VPN.

 
 

After DHCP Relay configuration, on IP address renewal, Branch Office users would get IP Addresses from Head Office DHCP Server

Step 2: Forward DHCP Traffic to Head Office

You need to forward the DHCP traffic of the Head Office Cyberoam over the IPSec VPN Tunnel. You can forward the traffic by following the steps given below. 

1.  Logon to CLI Console via Telnet or SSH. You can also access the CLI Console by clicking  on the upper right corner of the Web Admin Console screen. 

    Note: 

    From firmware version 10.6.1 onwards, the Console button is visible to the Super Administrator ONLY

2.    Choose option 4. Cyberoam Console.

3.    Execute the following commands to route traffic over IPSec tunnel:

      console> cyberoam ipsec_route add host 172.16.1.5 tunnelname DHCPoverVPN

 

      Where:
      DHCP Server IP – 172.16.1.5
      VPN Tunnel name – DHCPoverVPN

4.    Execute the following command to NAT Cyberoam generated traffic: 

 

      console> set advanced-firewall cr-traffic-nat add destination 172.16.1.5 snatip 172.16.2.1

     Where:
     DHCP Server IP – 172.16.1.5
     Interface (LAN Interface of Branch Office) – 172.16.2.1 

 

The configuration above sends DHCP traffic from the Branch Office to Head Office.

 

 

 

 

 

                                                                                                                        Document Version: 2.1 – 8 September, 2015 

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