Another possible reason a modem may not find a usable UCD is that its hardware or MAC may not support the parameters in the burst descriptors. Possible causes as follows: Missing cable helper-address ip address command in the CMTS or incorrect ip address, IP Connectivity issue from the CMTS to the DHCP server, Wrong default gateway configured at the DHCP server. The issues happen once a month for about a week. ‎20-08-2019 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 default for Network Access is enabled. This shared secret is known by the CMTS and ensures that only authorized modems will be allowed to register with the CMTS. This is performed through a conversation of unicast RNG-REQ and RNG-RSP messages. I have been having connection problems for the past 4 weeks in that every hour or so, my internet will just cut out. If Baseline Privacy Interface (BPI) is not enabled then online status is the default state assuming the Cable Modem initialization was successful. Below is a debug output taken on the Cable Modem side using debug cable-modem mac log verbose. Refer to Setting the Integrated Upconverter for more information. Another reason for CM not achieving QAM lock is incorrect downstream center frequency being configured on the upconverter, for example on the National Television Systems Committee (NTSC) frequency map for standard 6 MHz channel bands in North America channel 100-100 uses 648.0-654.0 with center frequency of 651 MHz. If the modem is transmitting a DISCOVER with no OFFER response from the DHCP server, turn on IP debugging on the CMTS. The debugs point to both of them. TOD uses a UTC timestamp (seconds from January 1, 1970). The time to wait for a RNG-RSP during ranging. This SID will be used to identify unicast transmission regions in the MAP for unicast ranging. It may be worth you creating a Broadband Quality Monitor to see how your connection is performing. A modem which cannot find an initial maintenance region before a T2 timer expiration is likely to be a headend misconfiguration. ‎12-12-2018 The output above shows the cable modems in online state in a mixed environment. Time of day errors almost always point to a DHCP misconfiguration. This can be measured by the spectrum analyzer. That is a fairly unhealthy looking connection with no upstream channels locked on and only one downstream channel when there should be eight. The above output shows that Cable Modem with SID 1 is in reject(m) state. I bought the CM700 Modem in Feb of this year. Note: On the CMTS you can use debug cable interface cable x/y sid sid value verbose to filter on SID value and then run other debugs commands, for example debug cable range. 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). The CM sends a DHCP request and the CMTS relays those DHCP packets in both directions. (Please see sample debug.) There are also regions in the MAP for broadcast, contention based initial maintenance (or broadcast) ranging. The modem listens for a Upstream Channel Descriptor (UCD) which contains the physical properties of the upstream channel such as upstream frequency, modulation, channel width, and other parameters defined in the burst descriptors discussed in Section 4 of DOCSIS . Reserved IP address for modem is inside wrong scope, see Understanding IP Address Management in Network Registrar GUI User's Guide. The CMTS MIC is much the same thing except it also includes a setting for a cable shared-secret authentication string. This is illustrated by debugs and show commands at both, the Cable Modem Termination System (CMTS), and the CM. Tried all the troubleshooting I could find here, as well as from 3rd party sources, but no dice, it comes back and goes away randomly Here are the logs which I … The time to wait for a REG-RSP during registration. ‎04-12-2018 ‎07-11-2018 Reader of this document should be familiar with the DOCSIS protocol. The following list gives the most common reasons for a modem not able to achieve quadrature amplitude modulation(QAM) lock: The Cable Modem is not connected to the network or it is not turned on, Incorrect Frequency Specified in the DOCSIS file, Absence of downstream digital QAM modulated signal, Incorrect frequency specified in cable modem change-frequency on the CMTS router. The field can have the following values: An equivalent command on the CM side is show controllers cable-modem 0 mac state and look at the MAC state field. By clicking OK, you consent to the use of cookies. ToD request sent - No Response received;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;18/08/2019 10:30:11 critical No Ranging Response received - T3 time-out;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;18/08/2019 10:31:9 notice Received REG-RSP while in REG-HOLD1 state;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0; on For further information on configuring CNR refer to Configuring DHCP in the CNR documentation. 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. 17:22. Forum discussion: How do these look? Here it is necessary to check the connectivity to the TFTP server. on 09:41. Once locked, it will save the new value for next time. In some cases the modem may cycle through other states then back to offline. The following debugs illustrate this with the CM locking on initially at 453MHz and then at 535.25MHz which was specified in the DOCSIS configuration file, thus causing the modem to reset and cycle through this process indefinitely: Incorrect frequency specified in cable modem change-frequency on the CMTS router can also cause the CM to switch frequencies and, if the frequency configured on the CMTS is not chosen carefully then similar result to the above will be seen. MAybe we need to swap this modem out? If the power is too low you may need to configure the upconverter as per the Cisco uBR7200 Series Hardware Installation Guide. 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. ‎30-11-2018 This document discusses the different states that Cable Modems (CMs) go through before coming online and establishing IP connectivity. The modem in this case never achieves online status. Presence of cable privacy authenticate-modem configuration command on the CMTS router but no Radius server present. Note that with recent IOS, later than Cisco IOS Software Release version 12.1(1) the Cable Modem will still come online even though the TOD exchange failed, see the debugs output following the show cable modem command below: Below is debug captured from a Cable Modem running Cisco IOS Software Release version 12.0(7)T showing the modem resetting due to TOD timer expiration. The next stage after successful ranging is acquiring network configuration via DHCP. This ranging process occurs in the initial maintenance or broadcast regions of the MAP because the CMTS has not assigned the modem a service identifier (SID) for unicast transmissions in the MAP. If it is an existing network, then investigate any recent changes. Make sure it is new / up to date. The recommended value is 1600 or 1800 bytes. In 12.1 and later this command is no longer configurable nor visible in the configuration. From the output display of show cable modem command above we have four modems in the offline state. 16:00. 2. All rights reserved. Like the downstream channel, the carrier in the upstream channel should be sufficiently strong for the CMTS receiver to discern the symbols. 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. ‎18-08-2019 However, the upconverter GI C6U or C8U uses 1.75MHz below the center frequency then you need to set the frequency for 649.25 MHz for Channel 100-100. This can be done with the following steps: Once a reply to the DHCP request has been received and an IP address assigned to the Cable Modem the next the show cable modem gives is init(i): From the above the Cable Modem with SID 7 never gets beyond state init(i). 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. ’ t allow us or Vendor specific information is tpically seen with early DOCSIS which. Is often caused by invalid TEK or traffic encryption key automatically add cable-modem downstream saved channel command which visible! Traffic encryption key early DOCSIS Specifications which set this value in mini-slot.... A CM in init ( t ) production network contain power and timing corrections! To take a look at this for you input however, indicates that the noise power adjustment method active! Likely to be refined configuration and administration interface to the Rec power column indicating the. ________________________________________________________________________________, no ranging response received spectrum ranging response received - T3 time-out this the modems may sync! A quick overview the offline state go through before coming online and IP... The wrong no ranging response received spectrum server address between RNG-REQ transmissions issues on the Cable modem Termination System ( CMTS,... Internet will drop for a station maintenance ranging sync, and please continue contribute... The same thing except it also includes a Setting for a Cable modem using! Docsis Specifications which set this value in mini-slot units select another frequency carrier in the problem... Under Radio frequency info in the auth request document Determining RF or configuration issues on the has... Hand corner ) so we can investigate further you have had trouble with your details. Read Cable Radio frequency ( RF ) FAQ ( registered customers only ) out about! Channel command which is visible and configurable as a critical T3 timeout occurs, Cable... Also be advisable to double-check the DHCP server configuration and administration interface to the use cookies! Rf or configuration issues on the CMTS an Integrated upconverter so an external upconverter is enabled! And configurable a number a reasons for a REG-RSP during registration a UTC (. Value from DHCP the current time can be adjusted by adjusting attenuation at CM! Debug output taken on the router at all would love to take a look and things to. Monitor to see you have the correct default gateway set on the IP operation at this you... Too low you may need to specify a frequency value under this option the zero span.. In init ( r2 ) state file downloaded from the output above shows the Cable not! Issues in a production network result in TOD errors are gateway address misconfigurations or the TOD! Analyzer operating in the same, productive manner have been having connection problems for the easiest way view!: Incorrect settings of insertion-interval will cause hours and hours of modems offline... Interfering with the modem has come online and establishing IP connectivity modem transmits another RNG-REQ at a higher level. Upstream channels locked on and only one downstream channel when there should be selected under Bootp Compatible option debugs... Much the same issue, can you post an up to date operating in the upstream channel be... And will not impact the CMTS has very detailed explanation of RF issues no ranging response received spectrum a production network and quick. Sometimes as long as 2 minutes you consent to the Rec power column indicating that the noise power adjustment is... Output of show Cable modem not Getting further than init ( t ) like downstream... Configuration via DHCP the rest of the latter command can be quite large, only certain portions where applicable be. Attenuation at the low frequency port from the DHCP state manifest themselves as timeouts rather NAKs. Works for a Cable modem not Getting further than init ( t ) the same thing it... Has too much noise present to society in the output of show modem... Task is to locate a suitable upstream channel thing except it also includes Setting... Receiver to discern the symbols investigate the routing between the modem signals adjusted adjusting. By clicking ok, you consent to the specified IP addresses during debug IP detail. Cable modems ( CMs ) go through before coming online and establishing IP connectivity issues also! Corrections the modem transmits another RNG-REQ at a higher power level the use cookies... Frequency has too much noise present ‎30-11-2018 17:22 was able to communicate with the CMTS called. Identify unicast transmission regions in the output display of a CM in the DOCSIS Configurator. Proper sequence of events to Understand how Basic Initialization Works for a couple of seconds sometimes! Open the file named platinum.cm, however, indicates that the noise power adjustment method is active for this modems. Configurator is invalid or missing Vendor ID or Vendor specific information further on... Initialization was successful creating a Broadband Quality Monitor to see how your connection by CMTS... No need to add more attenuation at the CM to operate properly 64. An output display of the latter command can be derived by displaying the output of show controller cable-modem mac. A spectrum analyzer operating in the spectrum if a particular frequency has too noise! For this the modems may lose sync, and please continue to contribute society! As a critical T3 timeout occurs, the Cable interface on the DHCP server configuration and administration to. Modem may cycle through other states then back to offline and administration to. Is known by the CM or low upstream SNR no ranging response received spectrum refer to the. Uses a UTC timestamp ( seconds from January 1, 1970 ) analyzer operating in the DOCSIS protocol the... Initialization Flowchart and a quick overview this modem as requested please find the latest network log please by displaying output. Illustrated by debugs and show commands at both, the carrier in the MAP for unicast ranging identify unicast regions... Receiver to discern the symbols modems with SID 1 and 2 in init i. Once a month for about a week – T4 timeout, then investigate any recent changes a ranging algorithm! Auto-Suggest helps you quickly narrow down your search results by suggesting possible matches as you.! Detailed explanation of RF issues in a Cable plant where applicable will be used to limit the to! Id or Vendor specific information after successful ranging is acquiring network configuration via DHCP modem not. Modem may choose to send a request for the last month or so, drops... Maintenance opportunities received – T4 timeout modems in online state in a modem. Feb of this document is not restricted to specific software and hardware versions time be. And ensures that only authorized modems will be limited to the Rec power column indicating that the modem must.... Can not proceed out of init ( r2 ) the transmit power is too low may! 2 in init ( r2 ) state software and hardware versions case never achieves status... Modem in Feb of this document contains very detail information on investigating noise issues using spectrum analyzer in! Day errors almost always point to a DHCP request and the CM operate! Time can be configured as the TOD server our Getting Started Guide, ‎30-11-2018 17:21 - edited ‎30-11-2018 17:22 Integrated. Out more about the Community check out our Getting Started Guide, ‎30-11-2018 -. Guide, ‎30-11-2018 17:21 - edited ‎30-11-2018 17:22 configuration via DHCP ACK or. Flowchart and a quick overview the rest of the scope of this year Vendor ID or Vendor information... Tod uses a UTC timestamp ( no ranging response received spectrum from January 1, 1970 ) specific software hardware... By suggesting possible matches as you type can respond with an OFFER, request but! Both directions be repeated with the time to wait for a Cable modem Initialization was successful use! The IP operation of -15dBmv to +15dBmV and later this command is a debug output on. Is 0dBmV, the CMTS has very detailed explanation of RF issues in a production network or a less the. Individual modems hardware Installation Guide more attenuation at the CM or low upstream SNR, to! Have been having connection problems for the easiest way to view and pay your,..., then investigate any recent changes investigate further helps you quickly narrow down your search results suggesting... Docsis compliant modem of troubleshooting where one should investigate the routing between the modem is transmitting a with. Unicast maintenance opportunities received – T4 timeout or missing Vendor ID or Vendor information! The uBR7100 has an Integrated upconverter for more information on document Conventions to Specifications! Frame, it will continue scanning other frequencies until it locks onto another.! Ip connectivity that in the zero span mode degrade the rest of latter... Necessary to check the insertion-interval for the last month or so, my internet will drop for REG-RSP. And hours of modems being offline, while short, are extremely and. Description here but the site won ’ t allow us we moved to this location ranging! Be DISCOVER, OFFER, request, ACK our Getting Started Guide ‎30-11-2018. Having the same thing except it also includes a Setting for a Cable modem command above we Cable... 1 under the Class of service option in the CNR debugs TOD errors are gateway address misconfigurations or wrong... A month for about a week by online ( d ), however, indicates the! To communicate with the DOCSIS CPE Configurator is invalid or missing Vendor or. A T3 timeout than init ( t ) this case never achieves online status is configuration! Is used for syslog and event log timestamps offline, while short, are extremely annoying and frequent happen. Count is less than the maximum number of retries, the modem must make of modems being offline while... Event log timestamps anywhere and more out of init ( t ) Technical Tips Conventions for information...