logical grouping of network users and resources connected to administratively defined ports on a switch. The segmentation into VLAN
creates smaller collision and broadcast domains and enhances security. Layer 3 switches or routers are needed to route packets between VLANs.
Switch Fabric: group of interconnected switches.
Dynamic vs static VLANs: Dynamic VLAN determine a host’s VLAN assignment automatically from a MAC address table, protocols, or
applications. VMPS (VLAN Management Policy Server) can be used to set up a database of MAC address-to-VLAN mappings. A static VLAN is
one in which the administrator manually configured the port VLAN membership.
Access vs Trunk Links: Links that are part of one VLAN are access links. Devices attached to an access link are unaware of their VLAN
membership. Trunk links can carry up to 1005 VLANs. A scheme is needed to identify what VLAN a frame belongs to (called frame tagging). ISL
and IEEE 802.1q are two standards of frame tagging supported by Cisco switches.
Trunk Protocol: used with ISL or 802.1q to allow VLAN trunking.
ISL (Inter-Switch Link): proprietary to Cisco switches, and is used for FastEthernet or Gigabit Ethernet links only, on a switch port, router interface
or a compatible server NIC. The server will then be able to be on multiple VLANs. The original frame is encapsulated with a 26-byte header and a
4-byte Frame Check Sequence (FCS) footer rather than modified. The ISL frames are up to 1522 bytes, which is over the Ethernet maximum of
1518.
802.1q: IEEE standard for frame tagging, required when using non-Cisco equipment. Inserts a field into the frame to identify the VLAN.
LANE (LAN Emulation): Used to communicate multiple VLANs over ATM.
802.10 (FDDI): used to send VLAN information over FDDI. Uses a SAID field in the frame header to identify the VLAN.
VTP (VLAN Trunk Protocol): Protocol created by Cisco to manage all the configured VLANs across a switched internetwork and to maintain
consistency throughout the network. VTP allows an administrator to add, delete and rename VLANs which is then propagated to all the switches in
the switch fabric. A VTP server must be created (default on switches). The other switches client or transparent (forward VTP information but do not
accept updates) and must be on the same domain name to share information. Only the client does not store its configuration in NVRAM. The clients
will update their information when a packet with a higher revision number is received. Updates are sent every 5 minutes or when a change occurs.
Clients switches cannot make any changes, and transparent switches can make changes but the changes will remain local and not be broadcasted.
VTP Pruning: in order to reduce bandwidth, the VTP information will only be sent through trunk links which require the information. It is disabled
creates smaller collision and broadcast domains and enhances security. Layer 3 switches or routers are needed to route packets between VLANs.
Switch Fabric: group of interconnected switches.
Dynamic vs static VLANs: Dynamic VLAN determine a host’s VLAN assignment automatically from a MAC address table, protocols, or
applications. VMPS (VLAN Management Policy Server) can be used to set up a database of MAC address-to-VLAN mappings. A static VLAN is
one in which the administrator manually configured the port VLAN membership.
Access vs Trunk Links: Links that are part of one VLAN are access links. Devices attached to an access link are unaware of their VLAN
membership. Trunk links can carry up to 1005 VLANs. A scheme is needed to identify what VLAN a frame belongs to (called frame tagging). ISL
and IEEE 802.1q are two standards of frame tagging supported by Cisco switches.
Trunk Protocol: used with ISL or 802.1q to allow VLAN trunking.
ISL (Inter-Switch Link): proprietary to Cisco switches, and is used for FastEthernet or Gigabit Ethernet links only, on a switch port, router interface
or a compatible server NIC. The server will then be able to be on multiple VLANs. The original frame is encapsulated with a 26-byte header and a
4-byte Frame Check Sequence (FCS) footer rather than modified. The ISL frames are up to 1522 bytes, which is over the Ethernet maximum of
1518.
802.1q: IEEE standard for frame tagging, required when using non-Cisco equipment. Inserts a field into the frame to identify the VLAN.
LANE (LAN Emulation): Used to communicate multiple VLANs over ATM.
802.10 (FDDI): used to send VLAN information over FDDI. Uses a SAID field in the frame header to identify the VLAN.
VTP (VLAN Trunk Protocol): Protocol created by Cisco to manage all the configured VLANs across a switched internetwork and to maintain
consistency throughout the network. VTP allows an administrator to add, delete and rename VLANs which is then propagated to all the switches in
the switch fabric. A VTP server must be created (default on switches). The other switches client or transparent (forward VTP information but do not
accept updates) and must be on the same domain name to share information. Only the client does not store its configuration in NVRAM. The clients
will update their information when a packet with a higher revision number is received. Updates are sent every 5 minutes or when a change occurs.
Clients switches cannot make any changes, and transparent switches can make changes but the changes will remain local and not be broadcasted.
VTP Pruning: in order to reduce bandwidth, the VTP information will only be sent through trunk links which require the information. It is disabled
by default on all switches. Once pruning is enabled on a VTP server, it is enabled for the whole domain. VLAN 1 is the administrative VLAN and is not eligible for pruning.
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