Cisco DNCS System Release 2.7 3.7 4.2 Design Guide
4000358 Rev B
Guidelines for Configuring the DBDS for DOCSIS
2-11
DNCS and Server Configurations,
Continued
To allow a DHCP server to recognize DHCP DISCOVER messages coming from a
Cisco DHCT, the integrated cable modem of the DHCT sends the DHCPDISCOVER
message option 60 set to docsis1.0 and option 43 with option code 5 set to
sciatl:cm:4200. The DHCT CPE sends in the DHCPDISCOVER message option 60,
and option 43 with option code 5 both set to sciatl:dhct:model#. The model#
TFTP Server
field
should not be used as a key in the server since this will vary per DHCT model. The
intent is to use that field for troubleshooting purposes only.
The same TFTP server that you currently use for stand-alone cable modems can also
be used for integrated cable modems. However, the integrated cable modems may
require a different configuration file than the stand-alone cable modems for the
following two reasons:
•
•
When setting the Max CPE parameter in the integrated cable modem
configuration file, the operator must reserve 1 CPE slot to support traffic to the
DHCT CPE. For example, in order to allow 1 PC, that parameter needs to be set to
2. Therefore the Max CPE for integrated cable modem must always be
set
to n+1,
where n represents the number of allowed PCs. (An integrated cable modem using
a configuration file with a Max CPE field that is blank or that contains the value 0
or 1 will support no external (PC) CPEs.)
•
The integrated cable modem may require a different set of SNMP filters than the
stand-alone cable modem.
Optional Servers
In addition to the servers required for the DBDS network using DOCSIS, you must
also configure your Time of Day (TOD) and Domain Name Service (DNS) servers, if
used.
TOD Server
The TOD server provides a timestamp for logged DOCSIS events. The cable service
TOD Server
The TOD server provides a timestamp for logged DOCSIS events. The cable service
provider may use the same TOD server for both their integrated cable modems and
their stand-alone cable modems. However, a TOD server is not required for
integrated cable modems. The DHCT CPE does not use a TOD server.
DNS Server
The DNS server resolves names to IP addresses. A DNS server is not required for
DNS Server
The DNS server resolves names to IP addresses. A DNS server is not required for
DHCT CPE, but may be required for PC CPE that has a need for Internet access.
Only the PC CPE has direct Internet access.