VLAN Trunking Protocol

This is a Cisco proprietary protocol that is designed to ease Vlan database management, it has nothing to do with trunking. The concept is that a switch with a VTP server mode will propagate VLAN database down to all switches with VTP client mode. Sw2-3560 vlan database before a new vlan is added (VTP client) … Continue reading VLAN Trunking Protocol

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Catalyst Switch: Turn off trunking negotiation

To turn off dynamic trunking protocol (DTP) and use dot1q standard. It is recommended to turn off trunking protocol and put vtp to transparent mode, this is because a newly introduced Catalyst switch may form undesired switch topology and if the newly introduced Catalyst switch has a vtp revision number higher than the current switch … Continue reading Catalyst Switch: Turn off trunking negotiation

Catalyst Switch: No trunks is formed

I have connected two Cisco Catalyst 3560 switches together by a pair of fibre cables. No trunk was formed. The default interface configuration for Catalyst 3560 is dynamic auto, in Catalyst 3550 the default was dynamic desirable. Dynamic desirable is actively negotiating a trunk with another cisco catalyst switch, whereas dynamic auto is passively waiting … Continue reading Catalyst Switch: No trunks is formed

VACL: Restricting access using Vlan ACL.

VACL: Restricting access using Vlan ACL. by Cyrus Lok on Tuesday, June 8, 2010 at 11:28pm Create a list of traffic that you want to restrict the vlan to access, in this example I want to restrict vlan 30 and 40 from accessing ftp, www and telnet 3550-1(config)#ip access-list extended vacl-ftp-www-telnet 3550-1(config-ext-nacl)#permit tcp any any … Continue reading VACL: Restricting access using Vlan ACL.

Number of vlans that can be created for each cisco switch models

Number of vlans that can be created for each cisco switch models by Cyrus Lok on Monday, August 9, 2010 at 11:45pm 2950: standard ios supports up to 64 vlans, able to use vlan id from 1 - 4094. Enhanced image supports up to 250 vlans, able to use vlan id from 1 - 4094 … Continue reading Number of vlans that can be created for each cisco switch models