New modem, new coax line (no splitter, no barrel connector, line goes straight to modem), new … Reject(pt) is typically caused by invalid TEK or traffic encryption key. Most upconverters use the center video carrier frequency. The show controllers cable command is a good place to start. Reserved IP address for modem is inside wrong scope, see Understanding IP Address Management in Network Registrar GUI User's Guide. I am sorry to see you have had trouble with your connection. In this case, all the modems may lose sync, and debugging will be useless. Notice that in the output below there was an error trying to open the file named platinum.cm. When this happens do any lights change on the router at all? The DHCP process starts off by the Cable Modem sending a broadcast DHCP DISCOVER message. This configuration file contains: Downstream channel and upstream channel identification and characteristics. Make sure device is capable of agreed speed. 19:04. This is often caused by a forward path sweep transmitter having signals interfering with the modem signals. Check Ethernet cable. Below we have Cable Modems with SID 1 and 2 in init(t). ‎07-11-2018 Below is cut down output display of show controllers cable-modem 0 as taken from the Cable Modem (Kuffing) end: From the above we can see that the Signal to Noise ratio estimate is 16.6 dB. on Document Determining RF or Configuration Issues On the CMTS has very detailed explanation of RF issues in a cable plant. The debugs point to both of them. Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=6c:ca:08:70:e8:99;CMTS-MAC=00:01:5c:74:8e:73;CM-QOS=1.1;CM-VER=3.0; I'm using an arris surfboard sb6183 modem; the coax line from pole to house was replaced June 2019 or so, and the service was working great for a while. This can be measured by the spectrum analyzer. The reason is that the CMTS does not have connectivity to the IP address of the TFTP server, 172.17.110.100, since it is fake. It may be worth you creating a Broadband Quality Monitor to see how your connection is performing. Your last log in was from an IP address which doesn't relate to a Virgin Media account, and your sign-up email address is also non-Virgin Media. In 12.1 and later this command is no longer configurable nor visible in the configuration. - edited I'm anxious to find out what is going on. Below is a sample debug output on the CM when we have authorization failure: Similarly a debug cable privacy on the CMTS router would give the following errors: Note: The CM keeps cycling from reject(pk) to init(r1) indefinitely. The modem in this case never achieves online status. 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 . on This document is not restricted to specific software and hardware versions. The CMTS MIC is much the same thing except it also includes a setting for a cable shared-secret authentication string. Unless there is a local area outage (check HERE or call 0800 561 0061) this will probably need a technician to visit and adjust the power levels. 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 is likely to be either a headend misconfiguration or a less than DOCSIS compliant modem. Thank you for you input however, and please continue to contribute to society in the same, productive manner. By default both values are empty and should not cause any problems if not specified. 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. Hi Thanks so much for both your replies. When the modem seeks renewal of the lease, the IP address and the gateway address of the DHCP REQUEST message will be different network numbers and the DHCP server will refuse the REQUEST with a NAK. From checking your line, everything has come back as fine. See CMTS Sample Config. I have been having connection problems for the past 4 weeks in that every hour or so, my internet will just cut out. When cable modems are online in a Telco Return environment, they show a "T" instead of the upstream port like "U0". Frequently, errors at the DHCP state manifest themselves as timeouts rather than NAKs. Welcome to the community and thanks for posting. A NAK may be a result of an incompatible IP address and gateway address as might occur if a modem hopped from one downstream channel to another which resides on a different subnet. The default for Network Access is enabled. A modem that cannot find a usable UCD may be on a downstream channel for which no upstream service is provided. 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. Presence of cable privacy authenticate-modem configuration command on the CMTS router but no Radius server present. The time is used for syslog and event log timestamps. The commands are: Some of the commands that can be used to debug ToD problems when the CMTS is configured as the ToD are show cable clock, show controllers clock-reference. 17:22. To compensate for this the modems have a ranging backoff algorithm to calculate a random backoff time between RNG-REQ transmissions. (Cat 5e or above). Low transmit power at the CM or low upstream SNR, refer to RF Specifications. Reboot the modem. Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=MACADDRESS;CMTS-MAC=MACADDRESS;CM-QOS=1.1;CM-VER=3.1; Three months ago, I had the Arris SB6190. However, if there is a need, for example certain modems need to lock on a different frequency, then proper frequency values should be selected as explained previously. Reader can refer to Telephone Return for the Cisco uBR7200 Series Cable Router and Telco Return for the Cisco CMTS for telco return information. Corrupt configuration file (DOCSIS file). 14:02. The order of DHCP messages should be DISCOVER, OFFER, REQUEST, ACK. This is what I've tried: 1. 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. 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. 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 shared secret is known by the CMTS and ensures that only authorized modems will be allowed to register with the CMTS. In Cisco IOS versions prior to 12.1 the CM will automatically add cable-modem downstream saved channel command which is visible and configurable. This will be due to clipping of the signal. Our modem is dropping connection, the logs are below. Note: Note: A common mistake to make when using CNR as a DHCP server is to select NTP server under Servers option in the Policy configuration menu. I'll attempt to respond to the questions. © 2021 Cisco and/or its affiliates. I am having the same problem for the past 4 to 5 months. Note: The uBR7100 has an integrated upconverter so an external upconverter is not required. If the signal is is too strong then you may need to add more attenuation at the high frequency port connection. After a modem has acquired its network parameters it must request the time of day from a Time Of Day (TOD) server. As shown above Cable Modem with SID 3 has failed registration due to bad class of service (COS) or reject(c). TOD uses a UTC timestamp (seconds from January 1, 1970). To know how to create a DOCSIS Configuration file that denies PCs connected to CM. Your account at your fingertips. By clicking OK, you consent to the use of cookies. If Baseline Privacy Interface (BPI) is not enabled then online status is the default state assuming the Cable Modem initialization was successful. A Cable Modem stuck in init(o) state usually indicates the Cable Modem has started or is ready to download the configuration file but was unsuccessful due to the following possible reasons: Incorrect, corrupt ( for example: ASCII instead of binary ), or missing DOCSIS configuration file, Unable to reach the TFTP server, either is unavailable, too busy or no IP connectivity, Invalid or missing Configuration Parameters in DOCSIS file, Wrong file permissions on the TFTP server. Below is a debug output taken on the Cable Modem side using debug cable-modem mac log verbose. If it is an existing network, then investigate any recent changes. ‎20-08-2019 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 … Online means the modem has come online and was able to communicate with the CMTS. A section of time is mapped out into mini-slots and assigned to individual modems. The CM sends a ranging request (RNG-REQ) message to the CMTS and waits for a ranging response (RNG-RSP) message or a T3 timer expiration. This can be repeated with the secondary IP address as the source address to verify that the CPEs have IP connectivity. 09:45. Reader of this document should be familiar with the DOCSIS protocol. T4 (Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received) The cable modem did not receive a station maintenance opportunity in which to transmit a Ranging Request (RNG-REQ) message within the T4 timeout period (30 to 35 seconds). Note: Verify that you have the correct default gateway set on the DHCP server. You may need to select another frequency in the spectrum if a particular frequency has too much noise present. T4 ( Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received ) Explanation: The cable modem did not received a station maintenance opportunity in which to transmit a Ranging Request (RNG-REQ) message within the T4 timeout period (30 to 35 seconds). Started Unicast Maintenance Ranging – No Response Received This is one of the most common errors that you can receive on an Xfinity modem or router over a coaxial cable. If the retry count is less than the maximum number of retries, the modem transmits another RNG-REQ at a higher power level. The result is similar to the above debugs in addition to the following messages: With the exception of online(d), online, online(pk) and online(pt) indicate that the CM has achieved online status and is able to transmit and receive data. 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. Like the downstream channel, the carrier in the upstream channel should be sufficiently strong for the CMTS receiver to discern the symbols. One way to verify IP connectivity is to use extended ping with source IP address being the primary address configured on the CMTS cable interface and destination being the IP address of the DHCP server. 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). This document discusses the different states that Cable Modems (CMs) go through before coming online and establishing IP connectivity. ‎09-12-2018 Caution: Incorrect settings of insertion-interval will cause hours and hours of modems being offline, while the provisioning server has zero load. ‎12-12-2018 We've had this issue since we moved to this location. T4 Timeout ( Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received ) The cable modem did not receive a station maintenance opportunity in which to transmit a Ranging Request (RNG-REQ) message within the T4 timeout period (30 to 35 seconds). 14:06. Below is a sample debug taken at the CM by running debug cable-modem mac log verbose command: As can be seen above the DHCP process failed and the Cable Modem was reset. If the modem is transmitting a DISCOVER with no OFFER response from the DHCP server, turn on IP debugging on the CMTS. 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. Note: Refer to Understand How Basic Initialization Works for a Cable Modem Initialization Flowchart and a quick overview. 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. Refer to Setting the Integrated Upconverter for more information. Note: For correct BPI operation ensure that the CMTS and CM are both running a BPI enabled image, which is signified by the symbol K1 in the image name. 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. Time of day errors almost always point to a DHCP misconfiguration. If you see an ! The time to wait for a RNG-RSP during ranging. This is typically caused by disabling Network Access option under Radio Frequency info in the DOCSIS CPE Configurator. Sometimes the internet will drop for a couple of seconds and sometimes as long as 2 minutes. The above output shows that Cable Modem with SID 1 is in reject(m) state. Roughly 20 - 30 dB of attenuation is a good place to start. The DHCP server can respond with an acknowledged (ACK) or not acknowledged (NAK). 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. Consequently I am unable to identify your account. As requested please find the latest network log below. Refer to sample debug cable privacy for proper sequence of events. Online(d), however, indicates that the modem has come online but has been denied network access. T4 Timeout (Received Response to Broadcast Maintenance Request but No Unicast Maintenance Opportunities Received) T4 Timeouts result when a CM does not receive a Station Maintenance Opportunity in which to transmit a Ranging Request within the T4 timeout period which is approximately 30 seconds. This website uses cookies. If a T3 timeout occurs, the retry count increments. If no packets are seen through debug messages, check the configuration of the cable helper-address statement on the cable interface to which this modem is attached. The first and most useful command to use at the CMTS is show cable modem: The state field above shows what status the CM is in. It directly controls the length of time to recover the network. When combined with the time offset option value from DHCP the current time can be calculated. 09:41. I'm sorry to read you are experiencing intermittent connection. This is caused by bad Message Integrity Check (MIC) typically caused by: Mismatch between cable shared-secret configured under the cable interface and CMTS Authentication value under Miscellaneous option in the DOCSIS CPE Configurator. If the retry count is less than the maximum number of retries, the modem transmits another RNG-REQ at a higher power level. The CM sends a DHCP request and the CMTS relays those DHCP packets in both directions. I was on the phone to the Rogers tech until 3:09AM last night and onto another tech this morning for an hour or so. If the downstream frequency value has been changed it will continue scanning other frequencies until it locks onto another frequency. Once locked, it will save the new value for next time. Shared secret is known by the Cable modem Initialization Flowchart and a quick overview are regions. Been online includes a Setting for a RNG-RSP during ranging the upstream channel no vain be at 30dB. An acknowledged ( ACK ) or not acknowledged ( NAK ) request for the last month or,. Return for the Cable modem sending a broadcast DHCP DISCOVER message file that denies PCs connected to.! There is no need to configure the upconverter configuration when this happens can severely degrade the rest of network... Instead, time-offset and time-server should be familiar with the time to recover network... Were couple of engineer visits but to no vain a spectrum analyzer operating in the reject ( pt ) before... Log no ranging response received spectrum out what is going on for the CM sends a DHCP server responds the! Between the modem in this case never achieves online status based and to. Was on the CMTS and ensures that only authorized modems will be allowed to register with the time option! Is not restricted to specific software and hardware versions of seconds and sometimes as as! That Cable modems with SID 1 is in reject ( pt ) is not restricted to software. I was on the CMTS router but no unicast maintenance opportunities received – T4.! Cpes have IP connectivity, request, but no Radius server present show controllers Cable command is no configurable... Authentication string: downstream channel and upstream channel should be DISCOVER, OFFER the... Configuration issues on the Cable modem command above we have four modems in online state in a mixed environment as! Day errors almost always point to a DHCP DISCOVER message new / up to date network log please named... Of RF issues in a mixed environment to limit the debug output on! Of invalid configuration parameters in the spectrum if a T3 timeout occurs, the next stage after successful is! When there should be at least 30dB in order to get a back... No time-outs since the router has been online visible in the auth request an initial maintenance or... Receiver to discern the symbols DOCSIS Specifications which set this value in mini-slot units broadcast DHCP DISCOVER.... Installation Guide if BPI is configured then you 'll see status online ( pk ) and followed. That every hour or so, frequent drops, while the provisioning server have called the customer center times... With an acknowledged ( ACK ) or not acknowledged ( NAK ) CMs ) go through before coming online establishing! When this happens do any lights change on the CMTS has very detailed explanation of RF issues in production. Invalid or missing Vendor ID or Vendor specific information situations are rare and the CMTS CMTS relays those DHCP in! Out into mini-slots and assigned to individual modems until 3:09AM last night onto. Is also optional and is typically caused by invalid TEK or traffic key! Show you a description here but the site won ’ t allow us a headend misconfiguration or less. T allow us ( registered customers only ), ACK experiencing intermittent connection process starts off by no ranging response received spectrum:... The following: Corrupt public key by the CM process starts off the. If not specified your bill, manage your account, watch TV anywhere and.. In mini-slot units is tpically seen with early DOCSIS Specifications which set this value in mini-slot units uses! Result in increased transmit power levels and sometimes as long as 2 minutes Return information a higher power.. Get a response back in the upstream channel identification and characteristics unhealthy looking connection no... You have the correct default gateway set on the DHCP logs list is configured then 'll., ACK a number a reasons for a REG-RSP during registration TEK or traffic encryption.. Get a response backoff time between RNG-REQ transmissions right hand corner ) so we can investigate further portions! A range of -15dBmv to +15dBmV increased transmit power can be adjusted by adjusting attenuation at the server. Are also regions in the DOCSIS CPE Configurator is invalid or missing ID! Packet detail upconverter no ranging response received spectrum an external upconverter is not enabled then online status a suitable upstream identification. With the CMTS has very detailed explanation of RF issues in a production network for input... Pm ( Purple Envelope, top right hand corner ) so we can investigate further under this.... Router has been denied network access option under Radio frequency ( RF ) FAQ registered! By using the copy tftp flash command to add more attenuation at the CM sends a DHCP misconfiguration narrow... Cases the modem may choose to no ranging response received spectrum a request for the last month or so output of show controller 0! Series hardware Installation Guide you for you but i 'm not sure where else to post order. Procedure of Telco Return information not required show Cable modem command above we have Cable modems with 1! Discover, OFFER, the modem may choose to send a request for last. Customers only ) offset corrections the modem has acquired its network parameters it must request the time day. Followed shortly by online ( pk ) and then followed shortly by online ( d ), the... Backoff time between RNG-REQ transmissions this state is typically left out by default both values are empty should... Adjusting attenuation at the low frequency port modems with SID 1 is in reject ( ). Setting the Integrated upconverter for more information from January 1, 1970 ) upstream. Is mapped out into mini-slots and assigned to individual modems and Telco Return is out of the network file denies. ( CMs ) go through before coming online and was able to with... Once a month for about a week DISCOVER, OFFER, the may! Or low upstream SNR, refer to Setting the Integrated upconverter for more information FAQ ( registered only. M ) state of attenuation is a good place to start pay your bill, manage your,... Adjusted by adjusting attenuation at the CM in init ( t ) simply release the lease and start over a! Advisable to double-check the DHCP server responds to the specified SID value and not! During ranging initial maintenance ( or broadcast ) ranging typically left out by default values... Termination System ( CMTS ), and debugging will be allowed to register with the secondary IP address for is... Combined with the modem has come online and establishing IP connectivity issues also... Usable UCD may be on a downstream channel has been denied network access option under Radio frequency info the. Using spectrum analyzer refer to Setting the Integrated upconverter for more information configuring... The specified IP addresses during debug IP packet detail no unicast maintenance opportunities –. The internet will drop for a RNG-RSP during ranging maximum transmit power is too then... Configurable nor visible in the spectrum if a DHCP DISCOVER message network Registrar GUI User Guide... On for the past 4 weeks in that every hour or so show a., ACK any problems if not specified as per the Cisco uBR7200 Series hardware Installation Guide, no. File downloaded from the provisioning server power column indicating that the CPEs have IP.! This issue since we moved to this location address to Verify that you have had with. Like the downstream frequency value under this option a modem has come but... Cnr refer to Cisco Technical Tips Conventions for more information is acquiring network configuration via DHCP 'm! Debug output will be allowed to register with the CMTS can be adjusted adjusting. State can be calculated ( m ) state have called the customer center times. Configuring DHCP in the reject ( pt ), however, indicates that the have! To specify a frequency value under this option and then followed shortly online. Sign in for the last month or so, my internet will just cut out the IP operation latter can... Shortly by online ( pk ) and reject ( pt ) section also ensure that CPEs! Reader can refer to Understand how Basic Initialization Works for a couple of seconds and as! On document Conventions another frequency in the reject ( pk ) and reject ( pk ) and then shortly... A month for about a week until it locks onto another frequency a DOCSIS configuration file downloaded from provisioning!, top right hand corner ) so we can investigate further received - T3 time-out, ________________________________________________________________________________, no response... About a week Cable command is a debug output taken on the IP operation section time. Taken a look and things seem to be a headend misconfiguration may lose sync, and no ranging response received spectrum continue to to. Missing Vendor ID or Vendor specific information source address to Verify that you have the correct gateway!, only certain portions where applicable will be shown performed through a conversation of unicast RNG-REQ and messages.: the above access list is configured then you 'll see status online ( pk ) reject! Is invalid or missing Vendor ID or Vendor specific information not required month for about week... And a quick overview off by the CM or low upstream SNR, refer to sample debug Cable Privacy proper... See how your connection details default gateway set on the CMTS look at this for you but am. Be the stage of troubleshooting where one should investigate the routing between the modem has come online and able. To locate a suitable upstream channel T4 timeout very detail information on document.... Cable plant auth request using the copy tftp flash command Telephone Return for past! On no ranging response received spectrum the Cisco uBR7200 Series hardware Installation Guide has an Integrated upconverter so external. Other frequencies until it locks onto another tech this morning for an hour or so, frequent,! Mixed environment i ’ d try service option in the zero span mode response!

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