Cisco / Trunk Discovery Protocols

draft

Disable DTP

do show cdp
no cdp run
no cdp advertise-v2

or per interface

interface fa0/X
switchport nonegotiate
exit

CDP

show cdp neighbors
show cdp neighbors detail

Chapter: CDP Commands https://www.cisco.com/c/en/us/td/docs/ios/12_2/configfun/command/reference/ffun_r/frf015.html

show cdp neighbors https://www.cisco.com/c/m/en_us/techdoc/dc/reference/cli/nxos/commands/l2/show-cdp-neighbors.html

How could I know what is the native-vlan on the neighbor device? https://learningnetwork.cisco.com/thread/117744

CDP Neighbor over multiple vlans https://community.cisco.com/t5/other-network-architecture/cdp-neighbor-over-multiple-vlans/td-p/3082829

check CDP

show cdp
!clear cdp counters
!clear cdp table
show cdp entry * protocol
show cdp entry * version

eventually disable CDP

!config terminal
!no cdp run
!no cdp advertise-v2
!!cdp run
!!cdp advertise-v2
!end

disable per interface

!interface ...
!no ip address
!shutdown
!no cdp enable
!!cdp enable
!end

VTP

set vtp mode transparent

check your VTP Version, Domain, Revision

show vtp status

check operations and password setting

show vtp counters
show vtp password

check your configuration

show run | include vtp
show run | include vlan
!show interfaces
show interface fa0/1
show interface fa0/24
show interface gi0/1
show interface gi0/1 trunk
show interface gi0/2
show interface gi0/2 trunk

check your vlans

show vlan

vlan database
show
exit

RESOURCES

Command Line Reference

Cisco IOS Configuration Fundamentals Command Reference https://www.cisco.com/c/en/us/td/docs/ios/fundamentals/command/reference/cf_book.html

Chapter: Basic Command-Line Interface Commands https://www.cisco.com/c/en/us/td/docs/ios/12_2/configfun/command/reference/ffun_r/frf001.html

Command References https://www.cisco.com/c/en/us/support/ios-nx-os-software/ios-15-2m-t/products-command-reference-list.html

CLI Reference Guide https://www.cisco.com/c/en/us/td/docs/security/esa/esa10-0/cli/b_CLI_Reference_Guide/b_CLI_Reference_Guide_chapter_010.html

DTP

Disabling Dynamic Trunking Protocol (DTP) https://www.freeccnaworkbook.com/workbooks/ccna-security/disabling-dynamic-trunking-protocol-dtp

Disable DTP on a switch https://community.cisco.com/t5/switching/disable-dtp-on-a-switch/td-p/3328521

VTP

Understanding VLAN Trunk Protocol (VTP) https://www.cisco.com/c/en/us/support/docs/lan-switching/vtp/10558-21.html

Configuring VLAN Trunk Protocol (VTP) https://www.cisco.com/c/en/us/support/docs/lan-switching/vtp/98154-conf-vlan.html

Troubleshooting VLAN Trunk Protocol (VTP) https://www.cisco.com/c/en/us/support/docs/lan-switching/vtp/98155-tshoot-vlan.html

Cisco Discovery Protocol Configuration Guide, Cisco IOS Release 15M&T https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/cdp/configuration/15-mt/cdp-15-mt-book/nm-cdp-discover.html

How a Recently Inserted Switch Can Cause Network Problems https://www.cisco.com/c/en/us/support/docs/lan-switching/vtp/98155-tshoot-vlan.html#topic7

Reset the Configuration Revision Number https://www.cisco.com/c/en/us/support/docs/lan-switching/vtp/98155-tshoot-vlan.html#topic9

Switches not updating VLAN’s https://community.cisco.com/t5/other-network-architecture/switches-not-updating-vlan-s/td-p/510505

The VLAN configuration changes do not update on a switch due to the misconfiguration of the VTP and the “VLAN 1003 parent VLAN missing” error message appears https://community.cisco.com/t5/networking-documents/the-vlan-configuration-changes-do-not-update-on-a-switch-due-to/ta-p/3131447


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