Руководство По Проектированию для Cisco DNCS System Release 2.7 3.7 4.2
4000438 Rev B
Frequently Asked Questions
7-3
Questions and Answers,
Continued
Do both the DHCT CPE (RF) and cable modem (data) portions of the DOCSIS-
capable DHCT have IP addresses assigned to them?
Yes. The DHCP server assigns IP addresses to both the DHCT CPE and the cable
Yes. The DHCP server assigns IP addresses to both the DHCT CPE and the cable
modem.
If I press the Power button on the front of the DOCSIS-capable DHCT, will it turn
If I press the Power button on the front of the DOCSIS-capable DHCT, will it turn
off the cable modem as well?
No. The cable modem is always on until the power is disconnected from the DHCT.
No. The cable modem is always on until the power is disconnected from the DHCT.
The Power button simply toggles on-and-off the video portion of the DHCT.
Are there any differences in staging a DOCSIS-capable DHCT compared to other
Are there any differences in staging a DOCSIS-capable DHCT compared to other
Cisco DHCTs that are not DOCSIS-capable, such as the Explorer 3250?
Yes. Because the DOCSIS-capable DHCT has an internal cable modem, the staging
Yes. Because the DOCSIS-capable DHCT has an internal cable modem, the staging
process requires additional steps for the cable modem. As for previous generations
of Explorer DHCTs, each DHCT has an RF MAC address that must be made known
to the DNCS. The RF MAC address is present on the CD-ROM issued by Cisco for
each shipment of DHCTs, and is printed on the rear label of the DHCT.
The cable modem within the DOCSIS-capable DHCT uses the DHCT’s Ethernet
The cable modem within the DOCSIS-capable DHCT uses the DHCT’s Ethernet
MAC address. The Ethernet MAC address is one number higher than the RF MAC
address. DOCSIS registration is keyed to this MAC address. An IP address must be
issued to the cable modem by the cable system’s DHCP server. Depending on the
operator’s policy, this server may require prior knowledge of a DHCT’s Ethernet
MAC address before issuing an IP address. To implement this policy, DHCT
Ethernet MAC address may be manually loaded into the DHCP server, or entered
using custom scripts .
An alternative to prior knowledge of all DHCT Ethernet MAC address is to allow the
An alternative to prior knowledge of all DHCT Ethernet MAC address is to allow the
DHCP server to issue an IP address to the cable modem based on “option 43
suboption 5” in the DHCP DISCOVER/REQUEST message. This field identifies the
cable modem as residing within the DOCSIS-capable DHCT. This type of policy
requires that the operator enter a rule on the DHCP server so that the relevant field
is recognized.
Does the CMTS need to “talk” to the DNCS since the DOCSIS-capable DHCT
Does the CMTS need to “talk” to the DNCS since the DOCSIS-capable DHCT
will be interacting with both?
Ethernet connections between the CMTS and the DNCS must be present, but the
Ethernet connections between the CMTS and the DNCS must be present, but the
CMTS and DNCS do not need any customized host-to-host communication. As far
as the DNCS is concerned, the CMTS is merely an IP router or Ethernet bridge on the
path to the DHCT. From the CMTS perspective, the DNCS is simply a host that
legitimately communicates with selected CPE that resides on the CMTS’s RF
interface.