Author Archives: Vyacheslav

Reason for messages “Failure: System is busy, please retry after a while” on Huawei OLT

Once when executing commands in the Huawei SmartAX console, the MA5683T began to notice often the message:

Failure: System is busy, please retry after a while

As it turned out, the reason in my case was Zabbix, which every hour received SNMP levels ONT and drew graphics. SNMP requests from him were packed with packets of 30-50, separately for each port. I solved the problem by increasing the timeout in the Zabbix server configuration and the verification period for more hours, because OLT was slowly issuing information, Zabbix was not available, considered it inaccessible, paused briefly and sent requests again.
Also, in the settings of the Zabbix node, you need to uncheck “Use bulk requests”.

Installing and using iotop

iotop – a console program that displays statistics on the use of disk space.

You can install Debian, Ubuntu, Mint with the command:

sudo apt-get install iotop

In Red Hat, Fedora, CentOS:

yum install iotop

Normal startup:

iotop

Running with the option:

iotop OPTION

I’ll describe the possible startup options:
–version (view version)
-h (view help)
-o (display only active processes or threads that read or write, instead of displaying all)
-b (inclusion of non-interactive mode, convenient for example to output information to a file)
-t (display time in each line, for non-interactive mode -b)
-n NUMBER (the number of iterations after which the output will be executed, if not specified, then the output is not standardized)
-d NUMBER (the delay between iterations in seconds, you can specify not an integer, a standard value of 1)
-p PID (display statistics only for the specified processes / threads, standard for all)
-u USER (display statistics only for specified users, standard for all)
-P (display only processes)
-a (accumulation of statistics from the start of the launch of iotop)
-k (statistics in kilobytes)
-q (shortened view, some header lines are removed, when used with the -b option. There are more abbreviated, for example -qq without title names and -qqq without a general summary)

Active and passive FTP mode

FTP can work both in the active mode and in the passive mode.

In active mode, the client performs a control connection with the server, and the server makes a connection to the client for data transfer.
The passive control connection and data connection are made by the client himself.

Under the control connection is meant authentication and command transmission.
The control connection is executed by the client in both cases equally, from the client side from the dynamic TCP port 1024-65535 to the server port 21.

In the active mode after the control connection from the client, the FTP server connects to the client’s dynamic port 1024-65535 from its TCP port 20 for data transfer.
In the passive mode after the control connection from the client, the FTP server tells the client the number of the dynamic TCP port 1024-65535 to which it can be connected to the client for data transmission.

Speed limit on Ubiquiti devices

Suppose we need to limit the speed on the client antenna.
Accordingly, it is in the station mode and is connected to the access point.

For restriction, we go to the web-based antenna management interface, open the Network tab, change the Configuration Mode: to Advanced, which will bring more parameters that you can configure .

At the very bottom, click on Traffic Shaping, check the Enable checkbox and specify the desired speed limit for WLAN0 or LAN0.
For example, you need to limit the reception speed to 5Mb/s and send up to 512Kbps, for reliability, we’ll specify a limit for both network interfaces, where Ingress is specified for WLAN0 5120, and for LAN0 512, respectively, for Egress, vice versa, WLAN0 – 512, and LAN0 – 5120, burst is left unchanged, that is, 0.

To apply the changes click below Change and then above Apply, after which the antenna configuration will reboot.

On the access point, alas, you can not limit the speed for each client, if you do the above settings (in reverse order), then the overall speed for all clients will be limited. In this case, you can cut the speed, for example billing, by turning on the Advanced tab Client Isolation in the Advanced tab so that clients do not see each other on the network and do not exchange traffic.

Done.

Configuring ACL on Ubiquiti devices

Let’s say we want to configure the ACL (access control list) on the Ubiquiti access point.

In the web interface of the device, open the tab “Wireless“.

At the very bottom opposite “MAC ACL:” tick the “Enable“.

And choose “Policy:“, on “Allow” (means that there will be devices on the list that are allowed to connect, all who are not registered – can not) or “Deny” (in the list of devices that can not be connected, and everyone else can).

By clicking on the button “ACL…“, in the opened window to add the device, in the first field we indicate its MAC, in the second one any desired description and click “Add“, later “Save“.
And the last stage is at the top click the button “Apply“, after which the changes are saved and applied without loss of communication with the device (without rebooting).