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Configuring Centralized DHCP Scope

The Centralized DHCP scope supports L2 and L3 clients.

When a centralized DHCP scope is configured:

The Virtual Controller does not assign an IP address to the client and the DHCP traffic is directly forwarded to the DHCP Server.
For L2 clients, the Virtual Controller bridges the DHCP traffic to the controller over the VPN/GRE tunnel. The IP address is obtained from the DHCP server behind the controller serving the VLAN/GRE of the client. This DHCP assignment mode also allows you to add the DHCP option 82 to the DHCP traffic forwarded to the controller.
For L3 clients, the Virtual Controller acts as a DHCP relay agent that forwards the DHCP traffic to the DHCP server located behind the controller in the corporate network and reachable through the IPSec tunnel. The centralized L3 VLAN IP is used as the source IP. The IP address is obtained from the DHCP server.

You can configure Centralized DHCP scope by using the Instant UI or CLI.

In the Instant UI

To configure a centralized DHCP scope:

1. Click More>DHCP Server. The DHCP Server window is displayed.
2. To configure a Centralized DHCP scopes, click New under Centralized DHCP Scopes. The New DHCP Scope window is displayed. The following figure shows the contents of the New DHCP Scope window.

Figure 1  New DHCP Scope: Centralized DHCP Scope

3. Based on type of DHCP scope, configure the following parameters:

Table 1: DHCP Mode: Configuration Parameters

Name

Description

Name

Enter a name for the DHCP scope.

VLAN Specify a VLAN ID. To use this subnet, ensure that the VLAN ID specified here is assigned to an SSID profile. For more information on SSID profile configuration, see Configuring VLAN Settings for a WLAN SSID Profile and Configuring VLAN for a Wired Profile
DHCP relay Select Enabled to allow the IAPs to intercept the broadcast packets and relay DHCP requests.
Helper address Enter the IP address of the DHCP server.
VLAN IP Specify the VLAN IP address of the DHCP relay server.
VLAN Mask Specify the VLAN subnet mask of the DHCP relay server.
Option82

This option is available only if Centralized is selected. Select Alcatel to enable DHCP Option 82 to allow clients to send DHCP packets with the Option 82 string.

The Option 82 string is available only in the Alcatel (ALU) format. The ALU format for the Option 82 string consists of the following:

l Remote Circuit ID; X AP-MAC; SSID; SSID-Type
l Remote Agent; X IDUE-MAC
4. Click OK.

 

The Option 82 is specific to Alcatel and is not configurable in this version of Instant.

The following table describes the behavior of DHCP Relay Agent and Option 82 in the IAP.

Table 2: DHCP Relay and Option 82

DHCP Relay

Option 82

Behavior

Enabled

Enabled

DHCP packet relayed with the ALU-specific Option 82 string

Enabled

Disabled

DHCP packet relayed without the ALU-specific Option 82 string

Disabled

Enabled

DHCP packet not relayed, but broadcast with the ALU-specific Option 82 string

Disabled

Disabled

DHCP packet not relayed, but broadcast without the ALU-specific Option 82 string

In the CLI

To configure Centralized DHCP scope for L2 clients:

(Instant Access Point)(config)# ip dhcp <profile-name>

(Instant Access Point)(DHCP Profile <profile-name>)# server-type <centralized>

(Instant Access Point)(DHCP Profile <profile-name>)# server-vlan <vlan-ID>

(Instant Access Point)(DHCP Profile <profile-name>)# option82 alu

(Instant Access Point)(DHCP Profile <profile-name>)# end

(Instant Access Point))# commit apply

(Instant Access Point))# commit apply

To configure Centralized DHCP scope for L3 clients:

(Instant Access Point)(config)# ip dhcp <profile-name>

(Instant Access Point)(DHCP Profile <profile-name>)# server-type <centralized>

(Instant Access Point)(DHCP Profile <profile-name>)# server-vlan <vlan-ID>

(Instant Access Point)(DHCP Profile <profile-name>)# dhcp-relay

(Instant Access Point)(DHCP Profile <profile-name>)# dhcp-server <DHCP-relay-server>

(Instant Access Point)(DHCP Profile <profile-name>)# vlan-ip <DHCP IP address> mask <VLAN mask>

(Instant Access Point)(DHCP Profile <profile-name>)# end

(Instant Access Point))# commit apply