Cisco Catalyst 3850 Configuration Guide

January 27, 2023
6:35 pm

How to perform Cisco Catalyst 3850 Configuration

Prerequisites for Cisco Catalyst 3850 Configuration

1. Rack-mount the switch
2. Connect the StackWise cables
3. Connect the switch ports
4. Perform power on
5. Provision your upstream switch
6. Connect at least one Ethernet cable from the uplink interface on the switch to the upstream switch or router

Cisco Catalyst 3850 Configuration and Setup Connection

For Cisco Catalyst 3850 Configuration, refer to the appropriate Cisco documentation for information on connecting to the switch to access the command-line interface (CLI)

Log In
Once you’re connected to the Cisco switch and have a terminal prompt, enter the following commands to log
in:

<switch-password (if prompted)>
enable
<config-password>

Cisco Catalyst 3850 Configuration for IP Address and Default Gateway

Firstly, determine the IP address, subnet mask, and default gateway values to which you want to configure the network switch. Secondly, type the following commands in the console with those values:

Switch# configure terminal
Switch(config)# interface vlan 1
Switch(config-if)# ip address <ip-address> <subnet-mask>
Switch(config-if)# exit
Switch(config)# ip default-gateway <default-gateway>
Switch(config)# end

Enable Spanning Tree PortFast on a Range of Ports

T0 enable the Spanning-Tree PortFast feature on a range of ports, use the following commands. Firstly, this feature should be enabled for any ports used for Igor nodes as it significantly reduces the delay time between when an Igor node is connected to a port. Secondly, when the switch allows network communication from the node to the Igor Gateway use the below commands:

Switch# configure terminal
Switch(config)# interface range Gi1/0/<starting port#>-<end port#>
Switch(config-if-range)# spanning-tree portfast
Switch(config-if-range)# end

Disable Spanning Tree PortFast on Specific Ports

These commands should be executed on any switch ports that will be connected to other switches, hubs or routers. Additionally, to disable the PortFast feature on a specific switch port, enter the following commands:

Switch# configure terminal
Switch(config)# int Gi1/0/<port#>
Switch(config-if)# no spanning-tree portfast
Switch(config-if)# end

Disable IGMP Snooping

This is a mandatory step to allow multicast traffic between the Igor Nodes and Gateway. To disable IGMP snooping on the switch, enter the following commands:

Switch# configure terminal
Switch(config)# no ip igmp snooping
Switch(config)# end

Enable LLDP

To enable LLDP, enter the following commands:

Switch# configure terminal
Switch(config)# lldp run
Switch(config)# end

Cisco Catalyst 3850 Configuration - Enable Perpetual PoE and Fast PoE on all Igor Node Ports

Following commands will enable the Perpetual PoE and Fast PoE features on a range of ports. Perpetual PoE provides uninterrupted power to connected PD devices even when the switch is still booting.

Fast Poe remembers the last power drawn from a particular port and switches on PoE power within 15 to 20 seconds after AC power is plugged-in without waiting for IOS to boot up. The combination of these two features means that the nodes will power on faster and turn on the lighting quicker, even before data communication has been granted:

Switch# configure terminal
Switch(config)# interface range Gi1/0/<starting port#>-<end port#>
Switch(config-if-range)# power inline port poe-ha
Switch(config-if-range)# end

Enable Telnet (Optional)

It is an optional step to enable telnet on the Cisco switch. Determine the value you want to use for the telnet password, and then enter the following commands:

Switch# configure terminal
Switch(config)# line vty 0 15
Switch(config-line)# password <telnet-password>
Switch(config-line)# end

Enable Jumbo Frames (Optional)

You can follow this step as an option to increase the allowed MTU packet size. This setting is important to use in an Igor network with multiple network switches interconnected via trunk ports to ensure no communication packets are dropped between the nodes and the Gateway.

To configure this setting, enter the following commands:

Switch# configure terminal
Switch(config)# system mtu 9000
Switch(config-line)# end

Verify the setting change by entering the following command:

Switch# show system mtu

Save Cisco Catalyst 3850 Configuration

From the switch prompt, execute the following commands. (See screen example below.)

Switch# copy running-config startup-config
[Enter]

Important: If the configuration changes are not saved, then the switch will return to the previous settings the next time it is rebooted.

Cisco Catalyst 3850 Configuration - Common Commands

Enable EXEC Commands

Switch> enable
Password: <switch-password>
Switch#

View Switch Hardware and IOS Software Versions

Switch# show version

View Status of All Switch Ports

Switch# show interface status

View PoE Power Status of All Switch Ports

Switch# show power inline

View Manually Set PoE Power Allocation for All Switch Ports

Switch# show power inline consumption

View Detailed PoE Power Status of a Specific Port

Switch# show power inline gi1/0/<port#> detail

View PoE Power Policing Status of All Switch Ports (Real-time Power Demand Limits)

Switch# show power inline police

View Recent Messages from Switch Log (Including Errors)

Switch# show log

Enable Console Log Messages

To enable Console Log Messages you may use below commands:

Switch# configure terminal
Switch(config)# logging console [severity-level]
Severity-level (Optional)

0 – Emergencies
1 – Alerts
2 – Critical
3 – Errors
4 – Warnings
5 – Notifications
6 – Informational
7 – Debugging (default)

Set Console Privileged EXEC Timeout

Switch# configure terminal
Switch(config)# line console 0
Switch(config-line)# exec-timeout minutes [seconds]
Switch(config-line)# end

Enable LLDP Globally on the Switch

Switch# configure terminal

Switch(config)# lldp run

View Switch LLDP Statistics

Switch# show lldp

View LLDP Neighbors

Switch# show lldp neighbors

View Detailed LLDP Neighbor Information

Switch# show lldp neighbors detail

Disable and Re-enable a Specific Port

(i.e., Cycle PoE Power on a Port)

Switch# configure terminal
Switch(config)# int gi1/0/<port#>
Switch(config-if)# shutdown
Switch(config-if)# no shutdown
Switch(config-if)# end

Enable Portfast Globally to Allow DHCP Request Within Five (5) Seconds

Switch# configure terminal
Switch(config)# spanning-tree portfast default
Switch(config)# end

Disable Portfast on Specific Ports Connected to Other Switches

Switch# configure terminal
Switch(config)# int gi1/0/<port#>
Switch(config-if)# spanning-tree portfast disable
Switch(config-if)# end

Cisco Catalyst 3850 Configuration - Power Management Modes - (Default Mode -- Auto)

Automatically allocates power to the PoE port after device detection. This is the default setting.

Switch# configure terminal
Switch(config)# int gi1/0/<port#>
Switch(config-if)# power inline auto
Switch(config-if)# end

Limit the Allocated Power Budget for Port Before Switch Discovers PD

Switch# configure terminal
Switch(config)# int gi1/0/<port#>
Switch(config-if)# power inline auto max <milliwatts>
Switch(config-if)# end

Set Static Allocated Power Level for Port Before Switch Discovers PD

The switch reserves this amount of power for the port even when no device is connected:

Switch# configure terminal
Switch(config)# int gi1/0/<port#>
Switch(config-if)# power inline static max <milliwatts>
Switch(config-if)# end

Force UPoE (60W) Power Availability from the Port via Four-Pair Mode

Switch# configure terminal
Switch(config)# int gi1/0/<port#>
Switch(config-if)# power inline four-pair forced
Switch(config-if)# shutdown
Switch(config-if)# no shutdown
Switch(config-if)# end

Cancel Port Settings

To cancel specific port settings, reissue the command with a “no” preceding it.
Example:

Switch(config-if)# no power inline static max

Cable Testing via Time-Domain Reflectometer (VDR)

For instructing the switch to run a TDR test on a specific interface, which helps determine if there’s a fault in the cable and approximately how far away from the switch that fault exists, enter the following command:

Switch# test cable tdr int gi1/0/<port#>
Show the results:
Switch# show cable tdr int gi1/0/<port#>

Cisco Catalyst 3850 Configuration - Switched Port Analyzer (SPAN) Port Mirroring and Monitoring

To send a copy of the traffic from the source port to the destination port on the switch, enter the following command. SPAN mirrors receive or transmit (or both) traffic on one or more source ports to a destination port for analysis:

Switch# configure terminal
Switch(config)# no monitor session all
Switch(config)# monitor session 1 source int gi1/0/<port#>
Switch(config)# monitor session 1 destination int gi1/0/<port#>