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Configuring Distributed DHCP Scopes

Instant allows you to configure the DHCP address assignment for the branches connected to the corporate network through VPN. You can configure the range of DHCP IP addresses used in the branches and the number of client addresses allowed per branch. You can also specify the IP addresses that must be excluded from those assigned to clients, so that they are assigned statically.

Instant supports the following distributed DHCP scopes:

Distributed, L2 — In this mode, the Virtual Controller acts as the DHCP server, but the default gateway is in the data center. Based on the number of clients specified for each branch, the range of IP addresses is divided. Based on the IP address range and client count configuration, the DHCP server in the Virtual Controller controls a scope that is a subset of the complete IP Address range for the subnet distributed across all the branches. This DHCP Assignment mode is used with the L2 forwarding mode.
Distributed, L3 — In this mode, the Virtual Controller acts as the DHCP server and the default gateway. Based on the number of clients specified for each branch, the range of IP addresses is divided. Based on the IP address range and client count configuration, the DHCP server in the Virtual Controller is configured with a unique subnet and a corresponding scope.

You can configure distributed DHCP scopes such as Distributed, L2 or Distributed,L3 by using the Instant UI or CLI.

In the Instant UI

To configure distributed DHCP scopes such as Distributed,L2 or Distributed,L3:

1. Click More>DHCP. The DHCP Server window is displayed.
2. To configure a distributed DHCP mode, click New under Distributed 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: Distributed DHCP Mode

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

Table 1: Distributed DHCP Mode: Configuration Parameters

Name

Description

Name

Enter a name for the DHCP scope.

Type

Select any of the following options:

l Distributed, L2— On selecting Distributed, L2, the Virtual Controller acts as the DHCP Server but the default gateway is in the data center. Traffic is bridged into VPN tunnel.
l Distributed, L3— On selecting Distributed, L3, the Virtual Controller acts as both DHCP Server and default gateway. Traffic is routed into the VPN tunnel.
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
Netmask If Distributed, L2 is selected for type of DHCP scope, specify the subnet mask. The subnet mask and the network determine the size of subnet.
Default router If Distributed, L2 is selected for type of DHCP scope, specify the IP address of the default router.
DNS Server If required, specify the IP address of a DNS server.
Domain Name If required, specify the domain name.
Lease Time Specify a lease time for the client in minutes.
IP Address Range

Specify a range of IP addresses to use. To add another range, click the + icon. You can specify up to four different ranges of IP addresses.

l For Distributed,L2 mode, ensure that all IP ranges are in the same subnet as the default router. On specifying the IP address ranges, a subnet validation is performed to ensure that the specified ranges of IP address are in the same subnet as the default router and subnet mask. The configured IP range is divided into blocks based on the configured client count.
l For Distributed,L3 mode, you can configure any discontiguous IP ranges. The configured IP range is divided into multiple IP subnets that are sufficient to accommodate the configured client count.

 

NOTE: You can allocate multiple branch IDs (BID) per subnet. The IAP generates a subnet name from the DHCP IP configuration, which the controller can use as a subnet identifier. If static subnets are configured in each branch, all of them are assigned the with BID 0, which is mapped directly to the configured static subnet.

Option Specify the type and a value for the DHCP option. You can configure the organization-specific DHCP options supported by the DHCP server. For example, 176, 242, 161, and so on. To add multiple DHCP options, click the + icon. You can add up to eight DHCP options.
4. Click Next.
5. Specify the number of clients to use per branch. The client count configured for a branch determines the use of IP addresses from the IP address range defined for a DHCP scope. For example, if 20 IP addresses are available in an IP address range configured for a DHCP scope and a client count of 9 is configured, only a few IP addresses (in this example, 9) from this range will be used and allocated to a branch. The IAP does not allow the administrators to assign the remaining IP addresses to another branch, although a lower value is configured for the client count.
6. Click Next. The Static IP tab is displayed. Specify the number of first and last IP addresses to reserve in the subnet.
7. Click Finish.

In the CLI

To configure Distributed,L2 DHCP scope:

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

(Instant Access Point)(DHCP Profile <profile-name>)# ip dhcp server-type <Distributed,L2>

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

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

(Instant Access Point)(DHCP Profile <profile-name>)# default-router <IP-address>

(Instant Access Point)(DHCP Profile <profile-name>)# client-count <number>

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

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

(Instant Access Point)(DHCP Profile <profile-name>)# lease-time <minutes>

(Instant Access Point)(DHCP Profile <profile-name>)# ip-range <start-IP> <end-IP>

(Instant Access Point)(DHCP Profile <profile-name>)# reserve {first|last} <count>

(Instant Access Point)(DHCP Profile <profile-name>)# option <type> <value>

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

(Instant Access Point))# commit apply

To configure Distributed,L3 DHCP scope:

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

(Instant Access Point)(DHCP Profile <profile-name>)# ip dhcp server-type <Distributed,L3>

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

(Instant Access Point)(DHCP Profile <profile-name>)# client-count <number>

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

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

(Instant Access Point)(DHCP Profile <profile-name>)# lease-time <minutes>

(Instant Access Point)(DHCP Profile <profile-name>)# ip-range <start-IP> <end-IP>

(Instant Access Point)(DHCP Profile <profile-name>)# reserve {first | last} <count>

(Instant Access Point)(DHCP Profile <profile-name>)# option <type> <value>

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

(Instant Access Point))# commit apply