Bootp/dhcp relay and source routing, Bootp/dhcp relay and authentication – Alcatel Carrier Internetworking Solutions Omni Switch/Router User Manual

Page 769

BOOTP/DHCP Relay

Page 26-5

In multiple group configurations, AutoTracker rules can be deployed to strategically support
the relay function. Two types of AutoTracker IP policies are appropriate for

DHCP

environ-

ments. The first is the IP protocol policy that puts all IP type frames into a single

VLAN

regard-

less of network address. The second is the

network policy that groups

users based on

their specific IP address.

Besides AutoTracker rules, the network administrator must be aware that some network envi-
ronments may contain

DHCP-

ready and non-

DHCP

clients. Such configurations are supported

by the switch’s

BOOTP

relay function.

BOOTP/DHCP Relay and Source Routing

In source route environments (where

VLAN

framing type is set for source routing) and

DHCP

clients are not directly attached to the switch but have one or more bridges between them,
the

mpx.cmd

file must be modified so that replies from the

DHCP

server can get through the

bridge.

Typically a router caches the client’s

RIF

information for source routing when the client

responds to an

ARP

, but if the client does not yet know its

address it cannot reply to an

ARP

and no

RIF

information is cached on the router. Unicast replies to the client before the

RIF is cached are discarded by the router. Forcing the

BOOTP

reply to be broadcast elimi-

nates this problem.

Use the

edit

command to make this change to the

mpx.cmd

file (see Chapter 7, “Managing

Files,” for instructions on using the

edit

command).

Add the following command:

bootpBcastReply=1

Reboot the switch to force the broadcast. Replies from the

DHCP

server to the client will be

broadcast from the router as

STE

ARE

packets so they can be sent through the bridge.

BOOTP/DHCP Relay and Authentication

Authentication clients may use

DHCP

to get an IP address. For Telnet authentication clients,

an IP address is required for authentication. The DHCP server may be located in the default
group, an authenticated group, or both. If authentication clients will be getting an IP address
from a

DHCP

server located in an authenticated group, a

BOOTP

DHCP

relay should be set up

using the

relayc

command described in this chapter.

In addition, the router port address of the authenticated group must also be configured for
the relay through the

avlbootpmode

command. See the Authentication Services chapter of the

the Switched Network Solutions User Manual for more information about this command.