No Slide TitleCisco 3 - LAN
Chapter 8
Typically in LAN configuration, users are grouped based on their location in relation to the HUB they are connected to.
Sales
Design
HUB
HUB
VLAN implementations offered a port-mapping that establishes a broadcast domain between default group of devices.
Switch
Switch
Admin
Students
Instructors
firewall
route processing & distribution
Routers are used to properly communicate between different VLANs. Use the routers as your backbone to transmit information at high bandwidth among your VLAN switches.
Routers in VLAN topologies provide
broadcast filtering
Communications between VLANs is by layer 3 routing
VLANs provide a method of controlling network broadcast
Network administrator assigns users to VLAN
VLANs can increase network security by defining which network nodes can communicate with each other
A VLAN is a broadcast domain that one or more switches create.
Cisco 3 - LAN
VLAN implementations offered a port-mapping that establishes a broadcast domain between default group of devices.
Switch
Switch
Admin
Students
Instructors
Ports that are assigned to the same VLAN share broadcasts.
Ports that do not belong to that VLAN do not share these broadcast.
There are two (2) methods in which to create VLANs:
Static VLANs –
This method is also referred to a port-based membership. As a device is connected to the network, it automatically assumes the VLAN of that port
Dynamic VLANs –
Dynamic VLANs are created through the use of software packages such as CiscoWorks 2000. With a VLAN Management Policy Server (VMPS), you can assign switch ports to VLANs dynamically based on the source MAC address of the device that is connected to the port.
Cisco 3 - LAN
Chapter 8
Static VLAN
The default VLAN for every port in the switch is VLAN1, or the management VLAN.
The management VLAN cannot be deleted; however, additional VLANs can be created and ports can be reassigned to these alternate VLANs.
A router is used to switch between different VLANs. Hence, each VLAN should have a unique Layer 3 network or subnet address assigned.
Cisco 3 - LAN
reduce administration costs related to solving problems associated with moves, additions & changes
20%-40% of the workforce physically moves each year
one can move the node to a new location without changing its’ IP / subnet address by plugging the node into port for that VLAN
controls broadcast activity
provide workgroup & network security
save money by keeping their HUBs and connecting them to switches i.e. don’t’ have to ‘throw away’ the HUBs.
The goal of the end-to-end VLANs, is to maintain the 80/20 traffic flow rule – 80% of the traffic on the local VLAN, and 20% on a remote VLAN.
Cisco 3 - LAN
Broadcast:
Switches (not talking about VLANs here) create ‘smaller collision’ domains, but they do not create smaller broadcast domains. Hence use routers which don’t propagate broadcasts.
Though by setting up the different VLANs on a switch, one can control the broadcast messaging from one VLAN to another.
Security:
restrict the number of users in a VLAN group
prevent another user from joining without first receiving approval from the VLAN network administrator
configure all unused ports to a default low-service VLAN
adding access list in the router
Cisco 3 - LAN
Using Hubs with VLANs
Each hub segment that is connected to a switch port can be assigned to only one VLAN.
All stations that share a hub segment become members of the same VLAN group.
Cisco 3 - LAN
Port-based VLANs (static):
nodes connected to ports in the same VLAN have same VLAN ID.
users are assigned by port
MAC address-based VLANs (dynamic):
VLAN Management Policy Server (VMPS)
are ports on a switch that can automatically determine their VLAN assignments
Protocol-based VLANs (dynamic):
are ports on a switch that can automatically determine their VLAN assignments
functions are based on:
VLAN Frame Identification
With multiswitch VLANs, the frame headers are encapsulated or modified to reflect a VLAN ID before the frame is sent onto the link between the switches.
Multiple trunking methodologies include:
Chapter 8
The most common approach for logically grouping users into distinct VLAN:
Frame Filtering
MAC
protocol
each frame is examined
depending on the ‘filter table’ sends the frame out the designated port
Cisco 3 - LAN
Chapter 8
Frame Identification
unique VLAN ID is assigned to each VLAN in the switch
the tagged frame travels the backbone among switches
when the frame exits the switch on non-backbone, the identifier is removed
this technique is chosen by IEEE (IEEE 802.1q)gaining as the standard trunking mechanism function at layer 2
Cisco 3 - LAN
VLAN2
Cisco 3 - LAN
ISL is a Cisco proprietary encapsulation protocol that interconnects multiple switches.
FDDI 802.10
Is a Cisco proprietary method of transporting VLAN information inside the standard IEEE 802.10 frame for Fiber Distributed Data Interface (FDDI).
Cisco 3 - LAN
LAN Emulation (LANE)
LANE is a standard defined by the ATM Forum that gives two stations attached via ATM the same capabilities they normally have if they are LANs such as Ethernet or Token Ring.
The function of the LANE protocol is to emulate a LAN on top of ATM network.
That is, the LANE protocols make an ATM network look and behave like an Ethernet or Token Ring LAN.
Cisco 3 - LAN
FACTS
VLAN makes up a switched network that is logically segmented by functions, project teams or applications, without regard to the physical location of users.
Each switch port can be assigned to a VLAN.
Ports assigned to the same VLAN share broadcasts.
So VLANs are used to create broadcast domains.
VLAN implementation methods used to assign a switch port to a VLAN:
port-centric
static
dynamic
2nd floor
1st floor
Only the devices on the same VLAN contend with collisions. Hence broadcast traffic within one VLAN is not transmitted outside the VLAN.
Cisco 3 - LAN
For configuring static VLANs on Cisco 29xx switches:
max number of VLANs is switch dependent & is limited by the number of ports on the switch.
VLAN1 is one of the factory-default VLANs
VLAN1 is the default Ethernet VLAN
Cisco Discovery Protocol (CDP) & VLAN Trunking Protocol (VTP) advertisements are sent on VLAN1.
Cisco 3 - LAN
NOTEs:
Some encapsulation protocol, such as 802.1q or ISL, must be configured on all switch trunks that participate in the VLAN.
commands for configuring VLANs vary by model number.
the catalyst 29xx IP address is in the VLAN1 broadcast domain.
switch must be in VTP server mode to create, add, or delete VLANs.
Cisco 3 - LAN
Chapter 8
For non-VLAN configuration, switches makes ‘smaller collision’ domain. However, they do not make ‘smaller broadcast’ domains. A broadcast messages is sent to all the devices connected to the switch.
Cisco 3 - LAN
Chapter 8
Switch B
Switch A
Use routers to reduce the broadcast of messages. A broadcast on Switch A is broadcast to all of its users, but is not broadcasted to Switch B (because the router won’t send it onto Switch B!)
Non-VLAN
Router
Cisco 3 - LAN
Switch#show vlan