Alcatel Carrier Internetworking Solutions Omni Switch/Router - 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 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.