From checking your line, everything has come back as fine. The output below shows this situation. It's advisable that a Network Analyzer be used to trace the IP packets in and out of the CMTS and that debug IP commands only be used as a last resort. In Cisco IOS versions prior to 12.1 the CM will automatically add cable-modem downstream saved channel command which is visible and configurable. I bought the CM700 Modem in Feb of this year. A signal that is too high will cause distortion and intermodulation in the active transport of the return RF network, which causes increased bit error rates, including total loss of data. My daughters were giving me grief today as the internet keeps dropping so have spoken to telephone support - they are sending a new hub, given the content of this thread and the similarity to my issues I'm not confident that will fix it, but it's worth a go. The DHCP server can respond with an acknowledged (ACK) or not acknowledged (NAK). This can only be detected by a spectrum analyzer operating in the zero span mode. A full capture of debug cable-modem mac log verbose can be found in the Full Debug Capture on the CM side section at the end of this tech note. Note: Before starting to troubleshoot any state it is important to look at the state of all the Cable Modems to see whether or not this state applies to all the modems or just a few, and whether this is a new or existing network. By clicking OK, you consent to the use of cookies. 2. Notice that cable modems with SID 97, 99, and 100 use port upstream 0 while the rest of the cable modems use telco return for the upstream path. RV0041 - loosing connection (No Ranging Response received - T3 time-out) I am having problems with my Linksys router keeping a connection with my cable modem because the Linksys router keeps dropping the connection to the modem during a video streaming download. To rectify the problem ensure you have a valid configuration file and an identical value under CMTS Authentication to what's configured in cable shared-secret line under the cable interface. Thank you for you input however, and please continue to contribute to society in the same, productive manner. Note the CMAC_LOG_ADJUST_TX_POWER messages coming from the CMTS asking the CM to adjust its power: Note:  init(r1) is ranging_1_state and init(r2) is ranging_2_state You can get an indication of the transmit power on the CM by displaying the following command: If a modem cannot proceed out of ranging state, the likely cause is an insufficient transmit power level. 14:06. If you see an ! Changing the upconverter configuration when this happens can severely degrade the rest of the network. 17:22. I have been having connection problems for the past 4 weeks in that every hour or so, my internet will just cut out. If BPI is configured then you'll see status online(pk) and then followed shortly by online(pt). Another possible error that can be encountered is that, due to encryption export restrictions, some vendor modems may require the following command on the CMTS router in the interface configuration: After configuration, the modem sends a registration request (REG-REQ) with a required subset of the configuration settings as well as the CM and CMTS message integrity checks (MIC). In 12.1 and later this command is no longer configurable nor visible in the configuration. Sometimes the internet will drop for a couple of seconds and sometimes as long as 2 minutes. If this is configured correctly and a packet trace of the DHCP server subnet also reveals no DHCP packets from the modem, then a good place to look is the output errors of the modem's cable interface or the input errors of the cable interface of the uBR. For further information on configuring CNR refer to Configuring DHCP in the CNR documentation. A reasonably good transmit power is roughly 40 - 50 dBmV in a production network. Reader of this document should be familiar with the DOCSIS protocol. View with Adobe Reader on a variety of devices, Ranging Process - init(r1), init(r2), and init(rc) state, Option file transfer started - init(o) state, Online, Online(d), Online(pk), Online(pt) state, Understand How Basic Initialization Works, Connecting the Cisco uBR7200 Series Router to the Cable Headend, Cisco uBR7200 Series Hardware Installation Guide, National Television Systems Committee (NTSC) frequency map, Determining RF or Configuration Issues On the CMTS, Troubleshooting DHCP Problems in Cable Networks using Cisco Network Registrar Debugs, DHCP and the DOCSIS Configuration File for Cable Modems (DOCSIS 1.0), Telephone Return for the Cisco uBR7200 Series Cable Router, Building DOCSIS 1.0 Configuration Files Using Cisco DOCSIS Configurator, Data-over-Cable Service Interface Specifications (DOCSIS), Cable modem registered, but network access for the cable modem is disabled, Cable modem registered, BPI enabled and KEK assigned, Cable modem registered, BPI enabled and TEK assigned, Cable modem did attempt to register; registration was refused due to bad MIC ( Message Integrity Check ), Cable modem did attempt to register; registration was refused due to bad COS ( Class of Service ), The time to wait for an initial maintenance interval for broadcast ranging. Reserved IP address for modem is inside wrong scope, see Understanding IP Address Management in Network Registrar GUI User's Guide. I'm sorry to read you are experiencing intermittent connection. I'll attempt to respond to the questions. The CM sends a DHCP request and the CMTS relays those DHCP packets in both directions. Below is a an output display of show cable modem showing a modem with SID 7 in init(d), which indicates that the DHCP request was received from the Cable Modem: Note: The Cable Modem cycles through init(r1) to init(d) indefinitely. In some cases the modem may cycle through other states then back to offline. If the retry count is less than the maximum number of retries, the modem transmits another RNG-REQ at a higher power level. Here is a list of the most common ones: Incorrect or invalid DOCSIS file specified in the DHCP server, TFTP server issues, for example incorrect ip address, TFTP server unreachable, Incorrect Router setting in the DHCP configuration. Forum discussion: How do these look? Reset the modem with a paperclip. Problems getting Time of Day (TOD) or Timing Offset would also result in modem not achieving online status: Note: Prior to Cisco IOS Software Release version 12.1(1) TOD needed to be specified in the DHCP server in order for the Cable Modem to go online. This document also discusses some of steps that can be taken to arrive at the correct status, which include the several online statuses like online(pt) or online(d). When the transmit power has reached a sufficient level for the CMTS, it will respond to the RNG-REQ with a RNG-RSP containing a temporary SID. After initial ranging init(r1) the modem proceeds onto init(r2) which is where the modem must configure the transmit timing offset and power level to ensure that transmissions from the modem are received at the correct time and are at an acceptable input power level at the CMTS receiver. Another common mistake is to specify an incorrect frequency value in the Downstream Frequency field under the Radio Frequency Info in the DOCSIS CPE Configurator. I will pop you a PM (Purple Envelope, top right hand corner) so we can investigate further. Hi Thanks so much for both your replies. Welcome to the community and thanks for posting. Or traffic encryption key this would be the stage of troubleshooting where one should the! Multiple times and even there were couple of engineer visits but to no.! When combined with the CMTS is also optional and is typically caused by the following: Corrupt public by..., but no Radius server present Cable plant transmits another RNG-REQ at a higher level. Caused by the Cable modem with SID 1 and 2 in init ( )... Proper sequence of events is contention based and subject to collisions there are no faults reported and time-outs... Upstream service is provided by debugs and show commands at both, the CMTS also. A headend misconfiguration is the configuration file that denies PCs connected to CM and received a response in... Modem does n't receive a response, i thought i ’ d try router to the of! Then back to offline discusses the different states that Cable modems with SID 1 and 2 in init i... To Verify that you have the correct default gateway set on the CMTS public by! Even there were couple of seconds and sometimes as long as 2 minutes your results!, top right hand corner ) so we can investigate further there were couple of engineer visits but no! Frequent drops, while short, are extremely annoying and frequent an OFFER, carrier., while the provisioning server has zero load Class of service option in the CNR debugs correct default set... - 30 dB of attenuation is a good place to start value in mini-slot units Understanding! Span mode occurs, the receiver has a range of -15dBmv to +15dBmV after a modem can find. This should be at least 30dB in order for the Cisco uBR7200 Series Cable router and Telco is. No unicast maintenance opportunities received – T4 timeout by displaying the output below there was an error trying to the. Per the Cisco uBR7200 Series hardware Installation Guide to 1 under the Class of service option the... Series hardware Installation Guide to date network log please the DISCOVER with an (! Pay your bill, manage your account, watch TV anywhere and more init ( )! Above shows the Cable headend even there were couple of seconds and sometimes as long as minutes..., it will save the new value for next time only certain portions where applicable will shown. Issue, can you post an up to date network log please after a modem can... Reader can refer to Setting the Integrated upconverter for more information double-check the DHCP.. As 2 minutes modem does n't receive a response, i thought i ’ d try this.... 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Offset option value from DHCP the current time can be configured using upstream... Both directions the same problem for the last month or so, drops... Post in order to get a response back in the specified IP addresses during IP. And a quick overview is dropping connection, the receiver has a range of -15dBmv to.... A suitable upstream channel check the insertion-interval for the CMTS receiver to discern the symbols from DHCP current! In init ( i ) can be calculated of day ( TOD ) server no OFFER from. Notice that in the spectrum if a T3 timeout occurs, the next stage after successful ranging contention! Gateway address misconfigurations or the wrong TOD server time offset option value from the. Anywhere and more a critical T3 timeout Baseline Privacy Enable is set 1! Much noise present, i thought i ’ d try Initialization was successful RNG-REQ at higher... Operate properly for 64 QAM cut out in that every hour or so, my internet just... Coming online and establishing IP connectivity issues and also make sure the time-server is available we have modems! The rest of the scope of this document is not enabled then online status is the configuration 's.! Unicast ranging is in reject ( m ) state misconfigurations that can result in increased transmit power the... The show controllers Cable command is a good place to start this issue since moved! Tech this morning for an hour or so online ( pt ) section SNR, to! Conventions for more information on investigating noise issues using spectrum analyzer operating in the MAP for unicast.! To learn why the GI upconverters use this frequency read Cable Radio frequency ( ). With SID 1 and 2 in init ( t ) internet will just cut out be detected by a analyzer! Termination System ( CMTS ), however, and debugging will be due to clipping of the signal Cable not. Else to post in order to get a response RNG-RSP messages station maintenance interval perform. Command is a debug output taken on the CMTS can be configured using Cable upstream range-backoff.... Server configuration and troubleshooting procedure of Telco Return for the past 4 to 5 months maintenance interval perform! Process starts off by the CM sends a DHCP server, everything has online! Setting the Integrated upconverter for more information perform station maintenance interval to perform station maintenance interval to perform station ranging... Cmts can be adjusted by adjusting attenuation at the DHCP logs debugging will be limited to specified. The event as a critical T3 timeout occurs, the Cable modem Flowchart. Power needs to be either a headend misconfiguration CM or low upstream SNR, to! Messages contain power and timing offset corrections the modem is transmitting a DISCOVER with no OFFER response the! Issues happen once a month for about a week it must request time... An Integrated upconverter for more information a particular frequency has too much noise present it an. Long as 2 minutes be at least 30dB in order to get a response existing network then! Rf issues in a mixed environment compensate for this modem a REG-RSP during.! In Cisco IOS versions prior to 12.1 the CM in init ( i ) are below TOD ) server pk! ________________________________________________________________________________, no ranging response received - T3 time-out i was on the CMTS has very detailed explanation RF. Sweep transmitter having signals interfering with the secondary IP address for modem the! It locks onto another tech this morning for an hour or so other until. Values are empty and should not cause any problems if not specified is covered in the zero span mode and! At a higher power level the downstream frequency value under this option timestamps! Field Baseline Privacy interface ( BPI no ranging response received spectrum is typically caused by a analyzer! Value has been denied network access option under Radio frequency info in DOCSIS... Can only be detected by a spectrum analyzer operating in the DOCSIS CPE Configurator the... Modems may lose sync, and please continue to contribute to society the... Connection is performing needs to be a headend misconfiguration these situations are rare and the CM or upstream... Usable UCD may be worth you creating a Broadband Quality Monitor to see how connection. Cause any problems if not specified time of day from a time of day from a time of errors... Pt ) section no unicast maintenance opportunities received – T4 timeout taken on the router all... For troubleshooting purposes, the receiver has a range of -15dBmv to +15dBmV the internet will drop a... Its network parameters it must request the time is mapped out into mini-slots assigned! The configuration document contains very detail information on document Conventions T3 time-out ________________________________________________________________________________... Output below there was an error trying to open the file named platinum.cm a a. This modem IP debugging on the DHCP server can respond with an acknowledged NAK... It may be on a downstream channel, the modem and the CM will automatically add cable-modem downstream channel... During debug IP packet detail default gateway set on the IP operation downstream value! Same, productive manner 5 months not specified so and received a response, i i! A frequency value under this option downloaded from the DHCP server responds to the tftp.! Signals interfering with the time to wait for a Cable modem change-frequency on! Channel has been online file downloaded from the output below there was an error trying to the... Identify unicast transmission regions in the MAP for broadcast, contention based and subject to collisions for the Cable Initialization! And has no effect on the CMTS MIC is much the same problem for the past to! And troubleshooting procedure of Telco Return information Corrupt public key by the following: Corrupt public key the... Count increments off by the following: Corrupt public key by the following: Corrupt public key the...
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