- Enterasys Security Router User's Guide

Utilizing the Command Line Interface
XSR User’s Guide 2-9
With bootp enabled, DHCP relay and server functionality is disabled on this DLCI for broadcast
packets entering from this DLCI. Unicast bootp requests are still forwarded to the server.
Configuration on a DLCI by DLCI basis is supported for a bootp response, requiring that a
statically-mapped DLCI number be configured with a corresponding IP address. This mapping is
valid for both point-to-point and multi-point sub-interfaces.
Since the XSR does not support an internal rDNS or a TFTP server, you must map the helper
address to the appropriate server in sub-interface mode with
ip helper-address A.B.C.D.
DHCP over LAN (RAI over Ethernet)
The DHCP over LAN client/server RAI employs a very fast installation for providing a running
configuration to an XSR. RAI over Ethernet retrieves a particular file from a TFTP server that will
be used to configure the remote router. This file will then be copied to Flash as the
startup-
config
and executed via normal startup procedures.
DHCP Client must be set on the XSR’s first Ethernet port. It sends a DHCP request several times
up to 18 seconds and if no response is received, RAI will proceed to the next RAI connection type.
The DHCP Client seeks the following information:
• IP Address - This mandatory data is required because the DHCP Server must assign a static MAC
address to the IP address
• Config file name - This optional data is needed otherwise a reverse DNS server is required.
• TFTP server address - This optional data is needed otherwise TFTP will send its initial message.
• Hostname - This optional data is not needed if the config file or an rDNS server are available
In practice, one of the following scenarios is played out:
• If the client receives an IP address only, it will request the hostname.domain via reverse DNS
and then a TFTP broadcast will be sent to find the file.
• If the client receives the config file name as well as the TFTP server address, then the TFTP
request will be initiated as a unicast message containing the DHCP config file name.
• If the client receives the hostname, reverse DNS will not be tried. The hostname will be used
only if the client config file name is not provided.
The DHCP application usually performs dynamic address assignment on a first-come, first-serve
basis from an address pool. For RAI to work properly, the DHCP server must statically map the
XSR’s MAC address to the IP address that will be used by reverse DNS. Failing to do so will cause
the XSR to try retrieving the wrong file from the TFTP server.
The DHCP Server seeks the following information:
• IP Address - This mandatory data is required because the DHCP Server must assign a static MAC
address to the IP address
• Config file name - This optional data is supplied by DHCP Option 67.
• TFTP server address - This optional data is supplied by DHCP Option 150.
• Hostname - This optional data is supplied by DHCP Option 12.
The XSR’s DHCP server feature is used by RAI over Ethernet but if a PC/Unix/Linux-based
application is available and meets the criteria for static assignment of IP addresses based on MAC
addresses, it may be used.