Qtech QSW-3900-48-SFP-DC [31/245] Loopback test command

Qtech QSW-3900-48-SFP-DC [31/245] Loopback test command
QTECH Software Configuration Manual
2-30
2.7.3 Loopback test command
In global configuration mode, loopback command is used to test exterior of all interfaces; in interface
configuration mode, loopback command is used to test whether the interface is normal, and it can be divided into
interior and exterior. When exterior testing, exterior wire must be inserted (receiving and sending lines of RJ 45
connected directly). Use 4 diferent wires when the speed is less than 100M.
Using loopback command to do the loopback test, interface cannot transmit data packet correctly, and it will
be automatically ended after a certain time. If shutdown command is executed, loopback test fails; when loopback
test is executing, speed, duplex, mdi, vct and shutdown operations are forbidden. After exterior test, pull out the
exterior wire to avoid abnormal communication.
Loopback on all interfaces :
loopback { internal | external }
Loopback on specified interface :
loopback { external | internal }
External means external loopback and internal means internal loopback
For example :
! Loopback on interface Ethernet 0/0/1
QTECH(config-if-ethernet-0/0/1)#loopback external
! Loopback on all interfaces
QTECH(config)#loopback internal
2.7.4 Remote access restriction
You can restrict host IP address or some network interface of switch by restricting web, telnet and snmp
agent, but other IP address without configuration cannot manage switch. By default, three server possess an address
interface of 0.0.0.0, so users of any IP address can manage switch. Different IP address and mask mean different
information. The mask in reverse which is 0.0.0.0 means host address, or it means network interface.
255.255.255.255 means all hosts. When enabling a configuration, an item of 0.0.0.0 must be deleted. When receiving
a packet, judge the IP address whether it is in the range of managed IP address. If it does not belong to it, drop the
packet and shutdown telnet connection.
login-access-list { web | snmp | telnet| telnet-limit } ip-address wildcard
Web means accessing IP address restriction of web server; snmp means accessing IP address restriction of
snmp agent; telnet means accessing IP address restriction of telnet; ipaddress means IP address; wildcard means
mask wildcard which is in the form of mask in reverse. 0 means mask this bit, and 1 meams does not mask this bit.
When mask in reserve is 0.0.0.0, it means host address, and 255.255.255.255 means all hosts. Use the no command to
delete corresponding item.
For example :
! Configure ip address allowed by telnet management system to be 192.168.0.0/0/255.255.0.0
QTECH(config)#login-access-list telnet 192.168.0.0 0.0.255.255
QTECH(config)#no login-access-list telnet 0.0.0.0 255.255.255.255
Use show login-access-list command to display all ip address allowed by web, snmp, telnet management
system.
show login-access-list
2.7.5 The number of Telnet user restriction
Configure the max number of Telnet users. This function can restrict the number of Telnet user (0-5) to enter
privileged mode at the same time. The user logged in without entering privileged mode will not be restricted but
restricts by the max number. Administrator and super user will not be restricted and can be logged in through series

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