Dhcp Server Options - Brocade Communications Systems FastIron SX 800 Configuration Manual

In some environments, it may be necessary to reassign network addresses due to exhaustion of the available address pool. In this case,
the allocation mechanism reuses addresses with expired leases.
Configuration notes for DHCP servers
• The DHCP server is supported in the Layer 2 and Layer 3 software images.
• The management VLAN or the management port must be enabled for a device to receive IP addresses from a DHCP server.
• In the event of a controlled or forced switchover, a DHCP client will request from the DHCP server the same IP address and
lease assignment that it had before the switchover. After the switchover, the DHCP Server will be automatically re-initialized on
the new active controller or management module.
• For DHCP client hitless support in an IronStack, the stack mac command must be used to configure the IronStack MAC
address, so that the MAC address does not change in the event of a switchover or failover. If stack mac is not configured, the
MAC address/IP address pair assigned to a DHCP client will not match after a switchover or failover. Furthermore, in the Layer
3 router image, if the stack mac configuration is changed or removed and the management port has a dynamic IP address,
when a DHCP client tries to renew its lease from the DHCP server, the DHCP server will assign a different IP address.
• If any address from the configured DHCP pool is used, for example by the DHCP server or TFTP server, you must exclude the
address from the network pool. For configuration instructions, refer to
on page 91.
• Ensure that DHCP clients do not send DHCP request packets with a Maximum Transmission Unit (MTU) larger than 1500
bytes. Brocade devices do not support DHCP packets with an MTU larger than 1500 bytes.
DHCP option 82 support
The DHCP relay agent information option (DHCP option 82) enables a DHCP relay agent to include information about itself when
forwarding client-originated DHCP packets to a DHCP server. The DHCP server uses this information to implement IP address or other
parameter-assignment policies.
In a metropolitan Ethernet-access environment, the DHCP server can centrally manage IP address assignments for a large number of
subscribers. If DHCP option 82 is disabled, a DHCP policy can only be applied per subnet, rather than per physical port. When DHCP
option 82 is enabled, a subscriber is identified by the physical port through which it connects to the network.

DHCP server options

A FastIron configured as a DHCP server can support up to 1000 DHCP clients, offering them the following options:
• NetBIOS over TCP/IP Name Server - Specifies a list of RFC1001/1002 NBNS name servers listed in order of preference.
• Domain Name Server - Specifies a list of Domain Name System (RFC 1035) name servers available to the client. Servers are
listed in order of preference.
• Domain Name - Specifies the domain name the client should use when resolving host names using the Domain Name
System.
• Router Option - specifies a list of IP addresses for routers on the client subnet. Routers are listed in order of preference.
• Subnet Mask - Specifies the client subnet mask (per RFC 950).
• Vendor Specific Information - Allows clients and servers to exchange vendor-specific information.
• Boot File - Specifies a boot image to be used by the client
• Next Bootstrap Server - Configures the IP address of the next server to be used for startup by the client.
• TFTP Server - Configures the address or name of the TFTP server available to the client.
FastIron Ethernet Switch Layer 3 Routing
53-1003627-04
Configuring IP parameters - Layer 3 switches
Specifying addresses to exclude from the address pool
85