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VDSL Flapping

Hi all,


Can someone help me on this? Cisco ISR4331 VDSL is flapping every minute.

We already checked the cables but no issues found.


Sep 22 19:10:19.112 AEST: %BGP-3-NOTIFICATION: sent to neighbor 4/0 (hold time expired) 0 bytes
000062: Sep 22 19:10:19.113 AEST: %BGP-5-NBR_RESET: Neighbor reset (BGP Notification sent)
000063: Sep 22 19:10:19.114 AEST: %BGP-5-ADJCHANGE: neighbor Down BGP Notification sent
000064: Sep 22 19:10:19.114 AEST: %BGP_SESSION-5-ADJCHANGE: neighbor IPv4 Unicast topology base removed from session BGP Notification sent
000065: Sep 22 19:10:22.168 AEST: %TRACK-6-STATE: 1 ip route reachability Up -> Down
000066: Sep 22 19:10:49.182 AEST: %VDSL_DAEMON-3-VDSL_LINE_UPDOWN: Controller VDSL 0/1/0, line 0, changed state to down
000067: Sep 22 19:10:49.182 AEST: %CONTROLLER-5-UPDOWN: Controller VDSL 0/1/0, changed state to down
000068: Sep 22 19:10:51.183 AEST: %LINK-3-UPDOWN: Interface Ethernet0/1/0, changed state to down
000069: Sep 22 19:10:52.183 AEST: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/1/0, changed state to down
000070: Sep 22 19:12:47.754 AEST: %VDSL_DAEMON-3-VDSL_LINE_UPDOWN: Controller VDSL 0/1/0, line 0, changed state to up
000071: Sep 22 19:12:47.754 AEST: %CONTROLLER-5-UPDOWN: Controller VDSL 0/1/0, changed state to up
000072: Sep 22 19:12:49.754 AEST: %LINK-3-UPDOWN: Interface Ethernet0/1/0, changed state to up
000073: Sep 22 19:12:50.754 AEST: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/1/0, changed state to

000074: Sep 22 19:12:55.268 AEST: %BGP-5-ADJCHANGE: neighbor Up
000075: Sep 22 19:13:37.184 AEST: %TRACK-6-STATE: 1 ip route reachability Down -> Up


Here are the updates from the Telco


We have interpreted the test results, please see the summary below:

1. MAC detected on LST and on VPNE is the same.

2. Sync went down when the customer unplugged the modem, which further rules out jumpering issue:

AVC Test Result details
Service Status
Operational Status Down
Service Stability UNSTABLE
Request Date
17:17 AEST

The service was in sync when the modem is connected:
Operational Status Up
Service Stability UNSTABLE

3. DSL Stability Profile: Stable

4. SELT is clear, no bridge tap detected.

As a result of the above, our next steps and action plan moving forward will be as follows:

1. SRA setting on the modem should be set to DYNAMIC

Seamless Rate Adaptation should be enabled as it allows the DSLAM port to request the modem to change bitrate (sync speed) without needing to drop sync.
As the Seamless Rate Adaptation Settings are disabled it would cause Intermittent Service/Dropouts.
Kindly change the Seamless Rate Adaptation (Seamless Rate Adaptation) settings in the Customer Premise Equipment to Dynamic and monitor the service for 2 days.

2. Make sure that dot1p is set to 0
3. Consider trying an alternate CPE


Here is the status of the controller VDSL 0/1/0

Controller VDSL 0/1/0 is UP

Daemon Status: UP

Chip Vendor ID: 'BDCM' 'BDCM'
Chip Vendor Specific: 0x0000 0xB1C5
Chip Vendor Country: 0xB500 0xB500
Modem Vendor ID: 'CSCO' ' '
Modem Vendor Specific: 0x4602 0x0000
Modem Vendor Country: 0xB500 0x0000
Serial Number Near: FOC2113611A 4331/K9 15.5(3)S4b
Serial Number Far:
Modem Version Near: 15.5(3)S4b
Modem Version Far: 0xb1c5

Modem Status: TC Sync (Showtime!)
DSL Config Mode: VDSL2
Trained Mode: G.993.2 (VDSL2) Profile 17a

TC Mode: PTM
Selftest Result: 0x00
DELT configuration: disabled
DELT state: not running

Failed full inits: 0
Short inits: 0
Failed short inits: 0

Modem FW Version: 4.14L.04
Modem PHY Version: A2pv6F039p1.d26d

Line 0:

Trellis: ON ON
SRA: disabled disabled
SRA count: 0 0
Bit swap: enabled enabled
Bit swap count: 299 0
Line Attenuation: 24.7 dB 0.0 dB
Signal Attenuation: 0.0 dB 0.0 dB
Noise Margin: 6.1 dB 21.3 dB
Attainable Rate: 51789 kbits/s 12947 kbits/s
Actual Power: 12.1 dBm 7.8 dBm
Per Band Status: D1 D2 D3 U0 U1 U2 U3
Line Attenuation(dB): 19.5 48.5 72.8 8.5 39.5 59.0 N/A
Signal Attenuation(dB): 25.0 48.2 N/A 8.5 39.0 N/A N/A
Noise Margin(dB): 6.1 6.0 N/A 24.0 21.1 N/A N/A
Total FECC: 6729332 0
Total ES: 54 0
Total SES: 54 0
Total LOSS: 1 0
Total UAS: 309 255
Total LPRS: 0 0
Total LOFS: 2 0
Total LOLS: 0 0

DS Channel1 DS Channel0 US Channel1 US Channel0
Speed (kbps): NA 49046 NA 7399
SRA Previous Speed: NA 0 NA 0
Previous Speed: NA 49096 NA 7399
Reed-Solomon EC: NA 3117618 NA 0
CRC Errors: NA 3133 NA 0
Header Errors: NA 0 NA 0
Interleave (ms): NA 0.00 NA 0.00
Actual INP: NA 69.00 NA 63.00


Not familiar with this VDSL configuration please help.




Enable Seamless Rate Adaptation (SRA) which adjusts your rate according to current line conditions.

router# conf t
router(config)# controller vdsl 0/1/0
router(config-controller)# shutdown
router(config-controller)# sra
router(config-controller)# no shutdown
router(config-controller)# end

router#show controller vdsl 0/1/0 | inc SRA:
SRA: enabled enabled

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