29 Nov 2020
Cisco proprietary Layer 2 protocol that is used to gather information about Cisco devices which share the same data link.
CDP is enabled by default. For security reasons, it may be desirable to disable CDP either globally or per interface. Its recommended to do not advertise to external networks.
Router# show cdp Router(config)# no cdp run Router(config)# interface ga 0/0/1 Router(config-if)# cdp disable
Show commands for displaying neighbour information
Router# show cdp neighbors Router# show cdp interface Router# show cdp neighbors detail
LLDP does the same thing as CDP, but it is not specific to Cisco devices.
To enable LLDP globally on a Cisco network device
Router(config)# lldp run
LLDP must be configured separately to transmit and receive LLDP packets.
Router(config)# interface ga0/1 Router(config-if)# lldp transmit Router(config-if)# lldp receive
The show commands are the same as Cisco’s CDP
Router# show lldp Router# show lldp neighbors Router# show lldp neighbors detail
It is important to synchronise the time across all devices on the network because all aspects of managing, securing, troubleshooting, and planning networks require accurate time stamping.
Manually set time and date
R1# clock set 16:01:00 sept 25 2020
NTP can be set up to synchronize to a private master clock, or it can synchronize to a publicly available NTP server on the internet.
NTP uses UDP port 123.
NTP networks use a hierarchical system of time sources. Each level in this hierarchical system is called a stratum.
Stratum 2 and Lower
The max hop count for Stratum servers is 15. A stratum 16, the lowest stratum level, indicates that a device is unsynchronized.
Time servers on the same stratum level can be configured to act as a peer with other time servers.
show clock provides the currently set date and time and if the system was manually (user) set or configured with NTP
R1# show clock detail 20:55:10.207 UTC Fri Nov 15 2019 Time source is user configuration
Set the NTP server.
R1(config)# ntp server 188.8.131.52
Review various details about the configured NTP server using the below commands.
R1# show ntp associations R1# show ntp status
Set the Router as NTP master
R1(config)# ntp master 1
SNMP is an application layer protocol that provides a message format for communication between managers and agents.
The SNMP system consists of three elements:
SNMP agents collect and store information about the device locally in the MIB.
The SNMP manager polls the agents and queries the MIB on UDP port 161.
SNMP agents send any SNMP traps to the SNMP manager on UDP port 162.
There are two primary SNMP manager requests, get and set.
|get-request||Retrieves a value from a specific variable.|
|get-next-request||Retrieves a value from a variable within a table; the SNMP manager does not need to know the exact variable name. A sequential search is performed to find the needed variable from within a table.|
|get-bulk-request||Retrieves large blocks of data, such as multiple rows in a table, that would otherwise require the transmission of many small blocks of data. (Only works with SNMPv2 or later.)|
|get-response||Replies to a get-request, get-next-request, and set-request sent by an Network Monitoring Sysytem (NMS).|
|set-request||Stores a value in a specific variable.|
An NMS periodically polls the SNMP agents that are residing on managed devices using the get request.
SNMP agents can generate and send traps to inform the NMS immediately of certain events.
The MIB organizes variables hierarchically, similar to a system registry. Each variable as an object ID (OID).
Cisco SNMP Object Navigator tool (Login Required)
OIDs are numbered, example:
Therefore, the OID is 184.108.40.206.4.1.9.
Data is retrieved via the
The most common method of accessing system messages is to use a protocol called syslog.
Syslog uses UDP port 514 to send event notification messages across IP networks
Nothing more important that level 0
|Severity Name||Severity Level||Explanation|
|Emergency||Level 0||System Unusable|
|Alert||Level 1||Immediate Action Needed|
|Critical||Level 2||Critical Condition|
|Error||Level 3||Error Condition|
|Warning||Level 4||Warning Condition|
|Notification||Level 5||Normal, but Significant Condition|
|Informational||Level 6||Informational Message|
|Debugging||Level 7||Debugging Message|
Syslog facilities are service identifiers
Some common syslog message facility codes reported on Cisco IOS routers include:
%LINK-3-UPDOWN: Interface Port-channel1, changed state to up
By default log messages are not timestamped to enable
R1(config)# service timestamps log datetime
Router# show file systems
This command provides useful information such as the amount of total and free memory, the type of file system, and its permissions.
Other common commands to navigate the directory include:
dir pwd cd
Backup and Restore
R1# copy running-config tftp Remote host ?192.168.10.254 Name of the configuration file to write[R1-config]? R1-Jan-2019 Write file R1-Jan-2019 to 192.168.10.254? [confirm] Writing R1-Jan-2019 !!!!!! [OK]
copy running-config usbflash0: Destination filename [running-config]? R1-Config
Enter the ROMMON mode.
Change the configuration register.
rommon 1 > confreg 0x2142 rommon 2 > reset
Copy the startup-config to the running-config.
Change the password.
Save the running-config as the new startup-config.
R1(config)# config-register 0x2102 R1(config)# end R1# copy running-config startup-config
Reload the device.
Backing up the IOS
RTA-1# copy flash tftp: Source filename ? c1900-universalk9-mz.SPA.151-4.M4.bin Address or name of remote host ? 172.16.1.2 Destination filename [c1900-universalk9-mz.SPA.151-4.M4.bin]? <cr>
Upgrade the IOS
copy the new IOS bin file to the device
R1# copy tftp: flash: Address or name of remote host ? 172.16.1.2 Source filename ? isr4200-universalk9_ias.16.09.04.SPA.bin Destination filename [isr4200-universalk9_ias.16.09.04.SPA.bin]
Switch the boot system to use the new .bin file and reload the device.
R1# configure terminal R1(config)# boot system flash0:isr4200-universalk9_ias.16.09.04.SPA.bin R1(config)# exit R1# copy running-config startup-config R1# reload