🛠️ Common Problems

Wrong time

It is extremely important that the time of the flow exporting router is properly configured, as well as accurate clock synchronization on the corresponding server.

ntpdate

The ntpdate package can help you set the time.

apt install ntpdate

Synchronize the time with Brazilian NTP servers provided by ntp.br.

ntpdate pool.ntp.br

Changing timezone

To change the timezone, use the following command:

dpkg-reconfigure tzdata

Incorrect ASN names?

asn-cache-names.json

All names are obtained through the whois tool and cached in the directory /opt/rr-flow-api/geo/asn-cache-names.json. This is to optimize the process, eliminating the need for repeated queries. If you encounter any issues with the names, you can edit this file.

Debugging tools

Here are some tools that can help identify issues.

tcpdump

The following command will help you identify if the router is correctly sending the data flow.

tcpdump -n udp port 3055 -T cnfp -c 10

nfcapd

Run the nfcapd (netflow) or sfcapd (sflow) command in debug mode and watch the incoming data in real time.

Netflow collection

nfcapd -E -p 3055 -w /tmp/

Sflow collection

sfcapd -E -p 3055 -w /tmp/

snmpwalk

Test SNMP connectivity using the snmpwalk command.

Example:

snmpwalk -v2c -c public 192.168.0.1
snmpwalk -v2c -c public udp6:[2001:db8::1]

snmpwalk -v2c -c public 192.168.0.1 .1.3.6.1.2.1.31.1.1.1.18

hdparm

Checking Disk Performance

If you are experiencing slowness in your application and suspect the disk may be the issue, follow these steps to check disk performance.

If the hdparm command is not installed on your system, install it using the command:

apt-get install hdparm

Get detailed information about the disk drive.

hdparm -I /dev/sda

Test the read speed of the drive with the following command.

hdparm -tT /dev/sda

/dev/sda:
 Timing cached reads:   37316 MB in  2.00 seconds = 18692.04 MB/sec
 Timing buffered disk reads: 1022 MB in  0.47 seconds = 2182.08 MB/sec

This will perform a read test on the drive and show the average and maximum transfer rates.

To test the write speed of the drive, run the following command:

hdparm -TtW /dev/sda

/dev/sda:
 Timing cached reads:   35522 MB in  2.00 seconds = 17791.90 MB/sec
 Timing buffered disk reads: 1022 MB in  0.46 seconds = 2230.83 MB/sec

This will perform a write test and also show the average and maximum transfer rates.