Juniper Networks G10 CMTS Flap List, Features for Troubleshooting, Cable modem flaps command

Features for Troubleshooting

•Flap List

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•	The CMTS maintains a database of cable modems, along with various statistics for each cable
•	modem. When a cable modem exhibits behavior that matches pre-defined criteria—referred
•	to as a flap—an entry is added to a table called a flap list. Each flap list entry contains the
•	MAC address of the cable modem, along with additional modem statistics that can assist in
•	determining why the cable modem flapped. You can display the flap list by issuing the show
•	cable modem flaps command.
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•	You can define global flap criteria or define flap criteria on an upstream interface basis. Flap
•	criteria defined for an upstream interface override those set at the global level. If a parameter
•	is not explicitly set, a flap is defined by its default value.
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•	After an entry is added to the flap list for a cable modem, any subsequent flap for that cable
•	modem, whether defined explicitly or by default, updates that flap list entry with new
•	statistics (including a flap count). Examples of flaps include excessive initial ranging, missed
•	station maintenance opportunities, large upstream power adjustments, and an SNR dropping
•	below a threshold.
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•	The flap list can be used to assist you with troubleshooting, locating CMTS and cable modem
•	configuration issues, and locating problems in the HFC plant without impacting throughput
•	and downstream performance, and without creating additional packet overhead throughout
•	the HFC network.
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•	For more information about the flap list, see the JUNOSg Software Configuration Guide:
•	Interfaces, Cable, Policy, and Routing and Routing Protocols.
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•Use the Flap List for Troubleshooting

•	To display the flap list, issue the show cable flap-listcommand:
•
•	user@host> show cable flap-list
•
•	MAC-Address	Interface Us/Port		IM	SM	PAdj	FAdj	SNR	MER
•	CER LTime	LEvnt	Total FAdjAmnt SNRavg MERavg CERavg
•	00:20:40:BF:5B:C4	ca-0/2/1	2/1	0	0	1	0	0	0
	0 Feb 18 12:04:21 PADJ FLAP		1	0		33	23	0
•
	00:E0:6F:03:16:DB	ca-0/2/0	9/0	0	0	13	0	0	0
•
	0 Feb 18 12:04:28 PADJ FLAP		13	0		28	24	0
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•	Table 45 on page 143 provides potential HFC plant issues associated with some of the flaps
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	and statistics displayed in the output fields. The quantification of the flap counts and statistics
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	is plant dependent, so general qualifications, such as High and Low, are provided.
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142 JUNOSg 3.0 G10 CMTS Hardware Guide