After successfully editing the MTP Hardware Filters the TIM is not receiving expected network packets.

Document ID : KB000045374
Last Modified Date : 14/02/2018
Show Technical Document Details

Problem:

Existing MTP Hardware Filters were working successfully with TIM receiving expected network packets and monitoring applications. However after expansion of those filters to add more IP Addresses problems started to occur but no errors received during the change:

  • The TIM has stopped monitoring applications.
  • The TIM is not receiving expected network packets as confirmed by the 5 minute Packet Statistics page and logs/protocolstats *.csv files i.e. pkts-capture is very high but pkts-forward is very low

 

Environment:

TIM running under MTP

 

Cause:

These types of log file error will be seen:

nqsnmptrap_<date>.log

20160804-10:32:41 mtpCaptureTrap - ERROR: Error setting hardware filter 'xxxx' for logical port 0. 

20160804-10:32:41 Trap not sent. No trap destination configured. 

nqnapacapd_<date>.log

10:42:59 Feed 0, Filter 7, Name 'xxxxx', Port Mask 01, Priority 10 

10:42:59 Command: Capture[Feed=0;Priority=10]=((((mIPSrcAddr==[...],...OR mIPDestAddr==[...]...) AND (mTCPSrcPort==443 OR mTCPDestPort==443)) AND (mIPv4Protocol==6)) AND Channel==0) 

10:42:59 Capture[Feed=0;Priority=10]=((((Data[DynOffset=DynOffIPv4Frame;...) 

10:42:59 ^ 

10:42:59 * * * Error: Internal error 

There are restrictions based on the number of items that can be specified on a single hardware filter. There is also a limit on the total number of hardware filters across all logical ports based on hardware resources. However determining that limit is not straightforward and it is usually based on trial and error.

 

Resolution:

Information about the current number of hardware filter resources currently being used can be found by logging into Linux using the netqos account and performing the following command while the nqcapd process is running:

sudo /opt/napatech/bin/NtplTool -expr "FilterInfo=All"

This gives the count of the various hardware resources being used. Note that the values are given in hex. 

The following table gives the limits for each type. 

Note: most of the MTP filters use the PatternCount in conjunction with the Group4PlusCount and Group8Count.

Parameter Max Value (hex)

SizeCount => 0x02

ProtocolCount => 0x08

ErrorCount => 0x08

PatternCount => 0x40

DynOffsetCount => 0x04

Group4PlusCount => 0x20

Group8Count => 0x20

SliceLookupCount => Unlimited (64)

SliceLengthCount => Unlimited (64) 

SearchCount => n/a n/a

The workaround for this problem is to create a second hardware filter for the same logical port to specify additional items (e.g. IP addresses). 

 

Additional Information:

Not Seeing Traffic. Is the issue on the MTP or TIM side?