Guidelines and limitations, Configuring a dhcp server – Cisco ASA 5505 User Manual

Page 348

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11-2

Cisco ASA 5500 Series Configuration Guide using the CLI

Chapter 11 Configuring DHCP

Guidelines and Limitations

Note

By default, the ASA 5505 ships with a 10-user license.

Guidelines and Limitations

Use the following guidelines to configure the DHCP server:

You can configure a DHCP server on each interface of the ASA. Each interface can have its own
pool of addresses to draw from. However the other DHCP settings, such as DNS servers, domain
name, options, ping timeout, and WINS servers, are configured globally and used by the DHCP
server on all interfaces.

You cannot configure a DHCP client or DHCP relay services on an interface on which the server is
enabled. Additionally, DHCP clients must be directly connected to the interface on which the server
is enabled.

The ASA does not support QIP DHCP servers for use with DHCP proxy.

The relay agent cannot be enabled if the DHCP server is also enabled.

When it receives a DHCP request, the ASA sends a discovery message to the DHCP server. This
message includes the IP address (within a subnetwork) configured with the dhcp-network-scope
command in the group policy. If the server has an address pool that falls within that subnetwork, the
server sends the offer message with the pool information to the IP address—not to the source IP
address of the discovery message.

For example, if the server has a pool in the range of 209.165.200.225 to 209.165.200.254, mask
255.255.255.0, and the IP address specified by the dhcp-network-scope command is
209.165.200.1, the server sends that pool in the offer message to the ASA.

Failover Guidelines

Supports Active/Active and Active/Standby failover.

Firewall Mode Guidelines

Supported in routed and transparent firewall modes.

Context Mode Guidelines

Supported in single mode and multiple context mode.

Configuring a DHCP Server

This section describes how to configure a DHCP server provided by the ASA and includes the following
topics:

Enabling the DHCP Server, page 11-3

Configuring DHCP Options, page 11-4

Using Cisco IP Phones with a DHCP Server, page 11-6

DHCP Monitoring Commands, page 11-8

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