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Virtual LAN (vlans) divides one PHYSICAL network into multiple BROADCAST domains. But, vlan-enabled SWITCHES cannot, by themselves, forward traffic across vlans boundaries. So you need to have routing between these vlans which is called inter vlan routing.

Virtual LAN (vlans) divides one physical network into multiple broadcast domains. But, vlan-enabled switches cannot, by themselves, forward traffic across vlans boundaries. So you need to have routing between these vlans which is called inter vlan routing.

The native vlan is the only vlan which is not TAGGED in a trunk, in other words, native vlan frames are transmitted UNCHANGED. PER default the native vlan is vlan 1 but you can change that:

#SHOW interface fa0/8 trunk.

#Port MODE encapsulation status native vlan

The native vlan is the only vlan which is not tagged in a trunk, in other words, native vlan frames are transmitted unchanged. Per default the native vlan is vlan 1 but you can change that:

#show interface fa0/8 trunk.

#Port mode encapsulation status native vlan

A trunk does add dot1q or ISL tags directly to frames and can EXIST on all or MULTIPLE vlans. While an access PORT only passes traffic from a set VLAN but does not modify the frame with a vlan TAG.

A trunk does add dot1q or ISL tags directly to frames and can exist on all or multiple vlans. While an access port only passes traffic from a set vlan but does not modify the frame with a vlan tag.

Maximum VLAN permitted in 802.1q is 4094.

Maximum vlan permitted in ISL is 1000.

Maximum vlan permitted in 802.1q is 4094.

Maximum vlan permitted in ISL is 1000.

Vlan frame TAGGING is a technology which is used to identify the vlan that the packet BELONGS to. The vlan frame tag is placed on the Ethernet frame when the Ethernet frame REACHES a switch from an access PORT, which is a member of vlan.

Vlan frame tagging is a technology which is used to identify the vlan that the packet belongs to. The vlan frame tag is placed on the Ethernet frame when the Ethernet frame reaches a switch from an access port, which is a member of vlan.

Show interface TRUNK.

Show interface fa1/0/13 trunk.

Show interface fa1/0/13 SWITCH PORT.

Show interface STATUS | INCLUDE trunk.

Show interface trunk.

Show interface fa1/0/13 trunk.

Show interface fa1/0/13 switch port.

Show interface status | include trunk.

DYNAMIC Trunking protocol is USED to automatically establish trunks between capable PORTS (insecure method).

Dynamic Trunking protocol is used to automatically establish trunks between capable ports (insecure method).

• Trunk: FORMS an UNCONDITIONAL trunk.
• Dynamic Desirable: Attempts to negotiate a trunk with the far end.
• Dynamic Auto: Forms a trunk only if requested by the far end.
• Access: It will NEVER FORM a trunk.

None negotiate command disables automatic FORMATION of trunk links. It will be GOOD to CONFIGURE trunk manually and GIVE none-negotiate command for SECURITY reason.

None negotiate command disables automatic formation of trunk links. It will be good to configure trunk manually and give none-negotiate command for security reason.

DYNAMIC Desirable: attempts to NEGOTIATE a TRUNK with the other END.

Dynamic Auto: forms a trunk only if REQUESTED by the other end.

Dynamic Desirable: attempts to negotiate a trunk with the other end.

Dynamic Auto: forms a trunk only if requested by the other end.

ACCESS MODE is used to connect END devices (host) to SWITCHES while trunk mode is used to connect between switches.

Access mode is used to connect end devices (host) to switches while trunk mode is used to connect between switches.

DELETE FLASH:vlan.dat

Delete flash:vlan.dat

NATIVE VLAN

Native vlan

ISL encapsulates ETHERNET FRAMES while 802.1q tags Ethernet frame.

ISL encapsulates Ethernet frames while 802.1q tags Ethernet frame.

There are two main types of Encapsulation Trunking PROTOCOLS.

1. ISL (INTER switch link) which is CISCO proprietary protocol.
2. 802.1q which is an IEEE standard.

There are two main types of Encapsulation Trunking protocols.

Router-on-a-stick is a TERM frequently used to describe a setup up that consists of a router and switch connected using ONE Ethernet LINK configured as an 802.1q TRUNK link. In this setup, the switch is configured with multiple vlans and the router performs all routing between the DIFFERENT networks/vlan.

Router-on-a-stick is a term frequently used to describe a setup up that consists of a router and switch connected using one Ethernet link configured as an 802.1q trunk link. In this setup, the switch is configured with multiple vlans and the router performs all routing between the different networks/vlan.

A switched virtual interface (SVI) is a VLAN of switch ports represented by ONE interface to a routing or BRIDGING system. There is no physical interface for the vlan and the SVI provides the layer 3 processing for packets from all switch ports associated with the vlan.

A switched virtual interface (SVI) is a vlan of switch ports represented by one interface to a routing or bridging system. There is no physical interface for the vlan and the SVI provides the layer 3 processing for packets from all switch ports associated with the vlan.

Vlan trunking protocol (vtp) is a cisco PROPRIETARY protocol that PROPAGATES the definition of virtual LOCAL area networks (vlan) on the whole local area network. To do this, vtp carries vlan INFORMATION to all the switches in a vtp domain. Vtp Advertisements can be SENT over 802.1q, and isl trunks.

Vlan trunking protocol (vtp) is a cisco proprietary protocol that propagates the definition of virtual local area networks (vlan) on the whole local area network. To do this, vtp carries vlan information to all the switches in a vtp domain. Vtp Advertisements can be sent over 802.1q, and isl trunks.