Alcatel Omni Switch/Router, User Manual

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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
IP
network policy that groups
IP
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
IP
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
or
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.