This document shows how to configure N+1 redundancy with the VCom
Readers of this document should have knowledge of RF Technologies and
The information in this document is based on the VCom HD4040
The information in this document was created from the devices in a
specific lab environment. All of the devices used in this document started with
a cleared (default) configuration. If your network is live, make sure that you
understand the potential impact of any command.
For more information on document conventions, refer to the
Cisco Technical Tips
In order to support redundancy switching, the cable modem termination
system (CMTS) needs to communicate to the upconverter Ethernet port to set
Simple Network Management Protocol (SNMP) Requests and to get SNMP
To communicate with and set up the upconverter, use a Cisco DB9 to
RJ-45 console adapter attached to the serial port of a computer. Use a console
(rollover) cable connected to the RS-232 port on the HD4040 upconverter (the
bottom RJ-45 jack). Make sure the upconverter “Z” module is selected for
Note: A straight, CAT5 Ethernet cable can be used with a special DB9 serial
adapter. You can make your own DB9 serial to RJ-45 adapter by attaching the
RJ-45 pins (or wires) to the DB9 pins as shown in this table:
RJ-45 Pin (Wire Color)
Go to HyperTerminal or some equivalent program.
To reach HyperTerminal from a Windows system, choose
Start > Programs > Accessories > Communications >
Set the upconverter to an appropriate serial port (such as
COM1) and set its baud rate to
Tip: Simultaneously press the Select key and
Down key on the upconverter for about 1 second to activate the
serial port. This only works if the SNMP function is disabled. You can also
cycle the power on the upconverter. You also may need to reboot your computer
for the COM1 port to activate.
Assign a valid IP address, Subnet mask, and gateway
Set the Read/Write SNMP Community Strings to
The default setting of public is not supported.
Refer to the Vecima
web site for more details and documentation.
Once an IP address is set up, SNMP will be operational. Attach an
Ethernet CAT5 cable to the RJ-45 jack on the back of the upconverter and to a
switch or hub common to all N+1 components.
Note: You can enable or disable SNMP operation through the Ethernet
port with an SNMP agent or using the VXR. The test command is test
hccp 1 1 channel-switch uc
snmp/front-panel, where uc is the name
assigned to the upconverter in the CMTS configuration file. “Working” or
“Protect” interfaces have to be configured on the CMTS for this command to
work. VCom has released a new version of code that allows you to use the front
panel SNMP-breakout feature. To disable SNMP mode on the HD4040 from the front
panel, hold down the Select button for approximately 6
seconds, then release it. If the upconverter is not SNMP-enabled and a failure
occurs, it goes into SNMP mode automatically; but it is best to place it into
SNMP mode manually with the test command. The
Protect upconverter frequency will automatically be set for the same frequency
as the Working upconverter or upconverters that it will be protecting, so there
is no need to assign it. Be sure to set the frequencies and power levels, and
be sure to enable the output on the Working modules and disable the output on
the Protect modules.
For non-SNMP capable upconverters to be used with the High Availability
solution, they need to have an RF output less than -3 dBmV—when intermediate
frequency (IF) input is absent—and a “ramp-up” time less than 1 second. If
neither of these requirements are met, the integrity of the high availability
system could be compromised. This solution is less expensive, has no Ethernet
connectivity concerns, has possibly quicker convergence time, and uses fewer
command-line interface (CLI) configurations in the CMTS.
One caveat to this solution is the downstream (DS) frequency must be
the same for an entire Hot Standby Connection-to-Connection Protocol (HCCP)
Group. One could still have different DS frequencies in a chassis,
In the new Cisco IOS® Software code, the configuration of an HCCP UPx
statement triggers IF output. If no HCCP UPx statement is present, then
IF-muting will be enabled (no IF output).
In the non-SNMP solution, the Protect upconverter frequency needs to be
set for the same frequency as the Working upconverter or upconverters that it
will be protecting. Be sure to set the frequencies and power levels, and be
sure to enable the output on the Working and Protect modules.
Note: The only way to set the power level is to have IF input from the
linecard. When IF-muting is enabled on the Protect interface and HCCP
configurations are present, issuing the cab downstream
if-output command is only cosmetic. This is the recommended
procedure to set the RF output on the Protect UPx:
Disconnect the Protect UPx RF Output cable from the cable
Before you configure HCCP commands, issue the cab
downstream if-output command to manually turn on the Protect
linecard IF output.
Set the UPx frequency and level.
Issue the no cab downstream if-output
command to turn off the Protect linecard IF output.
Configure the Protect linecard HCCP commands.
Connect the UPx cable back into the cable
Caution: Be sure the Protect UPx RF output cable is disconnected while you are
setting its RF output level. Once the Protect linecard cable is attached with
its IF muted, there will be no IF input and, hence, no RF output; the UPx RF
output cable, which is connected to the RF Switch, can be re-attached.
Tip: It may be advantageous to make the RF output of the Protect
upconverter slightly higher in level than the Working modules that it is
protecting. This is because of extra insertion loss through the switch when in
the Protect mode, which could be from 0.5 to 2 dB, depending on the frequency
Be sure to pick a standard NTSC center frequency. For example, channel
62 would be 451.25 MHz, so the visual carrier is 453 MHz center
It is recommended that you install a 10 dB pad on the upconverter input
to keep the 44 MHz IF input below 32 dBmV. It might be best to install the RF
attenuators on the IF input of the upconverter rather than on the IF output of
the linecard. This makes it easier to disconnect cables from the upconverter,
if necessary. The IF connectors are very close together and are not perfectly
round, which makes it easier to cross-thread; be careful.
Figure 1 - VCom HD4040 Upconverter – Rear
Modules are labeled as A through P and correlate to modules 1 through
16, when you are setting up the configurations in the 7200. The modules in
Figure 1 are shown from right to left because Figure 1 is the rear view.
Upconverter output cabling failures are covered in a switchover through
the “Keepalive” feature. The switch is not smart enough to detect any failures,
but the Protect VXR can detect failures and tell the switch what to do. The
best scenario is to monitor the MIBs from the upconverter; but, for now, the
Keepalive function indicates third party failures.
There are two test points on each upconverter module. The one on the
top is a -30 dB test point for IF input. The one below it is a -20 dB test
point for RF output. The LED between the two test points indicates RF output,
which means that there is no IF input or that it is disabled. The red LED at
the bottom indicates no IF input.
Figure 2 - VCom HD4040 Upconverter – Front
Note: The upconverter has its own redundancy feature, but do not enable it.
This feature is for upconverter redundancy when one IF signal is split to feed
two adjacent upconverter modules and the RF output is combined through a
splitter. SNMP takes care of this upconverter redundancy feature.
Note: Be sure that the upconverter is configured properly before you attach
the RF output cable to the switch. The Protect linecard IF of 44 MHz is active
even when the interface is “shut”. If the upconverter is enabled and sees IF
input, it could insert the signal on top of carriers that already exist. Be
sure to “enable” the upconverter to set its output power, then “disable” the
Protect upconverter module. It will “enable” its output and set the frequency
through SNMP when it needs to do so, based on the Working DS frequency
programmed in the 10K configuration.
Note: If you replace a bad upconverter while in the Protect mode, you must
“enable” it to set the power level. This creates another carrier to be placed
on the cable plant if the RF output is connected, which in most cases it will
be. The frequency would need to be set to the proper frequency and would be
stepping on the Protect upconverter frequency. The best way to set the level
and frequency would be through SNMP. For now, it is recommended that the
upconverter be set for the proper frequency and level while the RF output of
the upconverter is disconnected—this is easier and allows analyzer testing.
Then “disable” the output on the upconverter and connect the cable. This all
has to be done while SNMP is disabled, unless it can be done through
VCom has released a new version of code that allows you to update your
HD4040 upconverter cards from Rev 19 to Rev 20. This version also allows you to
upgrade the HD4008 controller to version 2.08. You must install this firmware
to take advantage of the new front panel SNMP-breakout feature.
To disable SNMP mode on the HD4040 from the front panel, hold down the
Select button for approximately 6 seconds, then release
Before you use the SNMP-breakout feature, you must also flash the SNMP
controller from a terminal session.
Once connected, you can either power cycle the unit or simultaneously
press the Select and Down buttons on the
front panel to restart the SNMP agent. This reboot causes a welcome screen and
menu to appear in the terminal connection.
Press 1 for Flash Update.
When prompted to begin the file transfer, select send text
file from the terminal server menu, then browse to file
Run the HD4000_302.exe program to update the flash of the controller.
The appropriate files will be loaded
Note: For this to work, the VCom HD4040 can not be in SNMP mode.
You will also find an updated MIB file (wcHD4040) with the added alarm
for SNMPAlarm, to indicate that SNMP has been disabled from the front panel.
The only way to re-enable SNMP is to set the MIB object
hd4000SNMPEnable to 1 or issue the
test hccp 1 1 channel-switch uc
The Dual4040D and MA4040D with SNMP modules are supported, but not as a
part of the reference design.
Read the MAC address of the Ethernet port of the
There is a white sticker on the Ethernet port which shows the
hardware address (the MAC address).
Create an Address Resolution Protocol (ARP) entry in the uBR7200
with this MAC address and the desired IP address.
The IP address is the one that you want to set on the Ethernet port
of the upconverter.
Router(config)# arp 10.10.10.1 MAC_address arpa
Connect the uBR7200 FE port to the Ethernet port of the upconverter
with a straight cable (through a hub).
The upconverter is a data terminal equipment (DTE) with 10BASE-T,
so a crossover cable works, if you are connecting directly to each
On the 7200, try to issue the telnet
command to reach the IP address and port of the upconverter Ethernet interface,
where the port number is 1.
This Telnet session will fail. It will, however, assign the IP
address to the Ethernet port of the upconverter.
!--- If you have created an ARP entry in the CMTS with the
!--- IP address 10.10.10.1 then issue this command:
telnet 10.10.10.1 1
Issue this telnet command, where
IP_address is the IP address of upconverter Ethernet
telnet IP_address 9999
You will be able to reach the upconverter now. You can set various
parameters from this Telnet session.
Tip: It may be possible to “hack into” the SNMP mode, if you press the
Up Arrow key when the “Z” module is highlighted. This will
make the address of the SNMP module change from 999 to 001, and SNMP should
manually disable. This trick does not work for the HD4040.