Interface status codes

Interface status codes can tell you whether an interface on a Cisco router or a switch is working. Status codes of an interface can be displayed using the show interface TYPE command, e.g.:SW1#show interface fa0/1 FastEthernet0/1 is up, line protocol is up (connected) Hardware is Lance, address is 0060.70d8.0001 (bia 0060.70d8.0001) BW 100000 Kbit, DLY 1000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation ARPA, loopback not set Keepalive set (10 sec) The first line Read more [...]

IOS files

Cisco devices usually use integrated flash memory to store IOS software images and other files (e.g. backup configuration files). The startup configuration is stored in NVRAM. For each memory device available on the device, a file system called IOS file system (IFS) is created. To list file systems available on your device, the show file systems EXEC mode command is used:R1#show file systems File Systems: Size(b) Free(b) Type Flags Prefixes * 255744000 221896413 disk Read more [...]

exec-timeout command

By default, an IOS device will disconnect a console or VTY user after 10 minutes of inactivity. You can specify a different inactivity timer using the exec-timeout MINUTES SECONDS line mode command.For example, to disconnect a console user after 90 seconds of inactivity, we can use the following command: R1(config)#line con 0 R1(config-line)#exec-timeout 1 30After 90 seconds of inactivity, the session will be disconnected and the user will need to supply the console password to log back in:R1(config-line)# R1 Read more [...]

Link Layer Discovery Protocol (LLDP)

Link Layer Discovery Protocol (LLDP) is a vendor-neutral link layer protocol defined in IEEE standard 802.1AB. Just like Cisco’s CDP, LLDP is used by network devices to advertise their identity, capabilities, and neighbors on a local Ethernet network. However, since LLDP is an open standard, it has one big advantage over CDP – it can be used on non-Cisco devices.LLDP is disabled by default on Cisco devices. To enable it, use the lldp run command in the config mode:R1(config)#lldp runTo Read more [...]

logging synchronous command

By default, IOS displays syslog messages to the console users at any time, even during the typing of a command. Consider the following example:R1(config-if)#ip address 192.168.0.100 255.2 %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0, changed state to down 55.255.0Notice how the command was interrupted and the syslog message was shown. To prevent this, the logging synchronous console line mode command is used:R1(config)#ip address 192.168.0.100 255.2 %LINEPROTO-5-UPDOWN: Line Read more [...]

Configure Cisco router as DNS client

DNS is anĀ  application layer protocol used to resolve hostnames to IP addresses. If you have a DNS server on your network, you can configure your Cisco device to use it for name resolution. Here are the steps:(Optional) If you’ve previously disabled DNS lookups on your device, re-enable it with the ip domain-lookup command.Specify the IP address of the DNS server using the ip name-server command. It is possible to specify up to six DNS servers.(Optional) Specify the domain name to append to Read more [...]