Cisco IOS // Trunk Discovery Protocols (CDP DTP VTP)

Disabling CDP

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

eventually disable CDP

config t
no cdp run
no cdp advertise-v2
exit

or per interface

config t
interface fa0/X
switchport nonegotiate
end

More on VTP

only pass the VTP advertisements through trunks

vtp mode transparent
!set vtp mode transparent

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 VTP Version, Domain, Revision

show vtp status

check operations and password setting

show vtp counters
show vtp password

Resources

CDP

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

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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