Vlan
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Transcript of Vlan
Chapter 3 - VLANs
VLANs
Logical grouping of devices or usersConfiguration done at switch via softwareNot standardized – proprietary software from vendor
VLANs
Logically segment the physical LAN infrastructure into different subnets (or broadcast domains for Ethernet)
Differences Between Traditional Switched LAN and VLANs
VLANs work at Layer 2 and Layer 3 of OSICommunications between VLANs is done by routersVLANs provide a method of controlling network broadcasts
Administrators assign users to VLANsVLANs increase network security – defines who can communicate with whomGroup switch ports and their connected users into logically defined workgroups
Transport of VLANs Across the Backbone
Ability to transport VLAN information between interconnected switches and routers that reside on the backbone– Remove physical boundaries between users– Increase configuration flexibility – users move– Provide mechanism for interoperability between
backbone components
VLAN transportation
Backbone commonly acts as collection point for large volumes of trafficCarries end user information and ID between switches, routers and directly attached servers
Routers in the VLAN
Traditionally provide firewalls, broadcast management etc.Provide connected routes between different VLANsCost effectively integrate external routers into switching architecture by using one or more high speed backbone connection like:– Fast Ethernet, or ATM connection
• Increasing the throughput between switches and routers
Frame Use in the VLAN
Switches core component of VLAN communicationEach switch makes forwarding and filtering decisions based on the frame– Based on VLAN metrics
Approaches for logically grouping users into distinct VLANs:– Frame filtering– Frame tagging (identification)
Frame Filtering
Frame Tagging
Uniquely assigns a VLAN ID to each frameVLAN IDs assigned by switch administratorChosen by IEEE for its scalabilityGaining recognition as the standard trunking mechanismIEEE 802.1q states that Frame Tagging is the way to implement VLANs
Frame Tagging Continued
Places a unique identifier in the header of each frame as it is forwarded throughout the networkWhen the frame exits the network backbone – switch removes the identifier before the frame is transmitted to its targetFrame identification functions at Layer 2 and requires little administrative overhead
Ports, VLANs and Broadcasts
VLANs make up a switched network – logically segmentedPorts assigned to the same VLAN share broadcastsThree VLAN implementation– Port-centric– Static– Dynamic
Port-Centric
All nodes connected to ports in the same VLAN are assigned same VLAN ID VLAN Membership by port make administrator’s job easier and more efficient because:
• Users assigned by port• VLANs easily administered• Increased security• Packets do not LEAK into other domains
Port-Centric VLANs
Static VLANs
Ports on switch that is statically assigned to a VLANRequire administrator to make changesSecureEasy to configureStraightforward to monitorWorks well in which moves are controlled and managed
STATIC VLANs
Dynamic VLANs
Ports on switch automatically determine their VLAN assignmentsBased on MAC addresses, logical addressing or protocol type of data packetLess administration with in the wiring closet when a user moves or new one addedCentralized notification when an unrecognized user is added to the networkMore administration is required to initially set up database within the VLAN management software
Dynamic VLANs
VLAN Additions, Moves and Changes
Companies continually reorganizing – These moves/changes are network manager’s biggest
headaches and one of the largest expenses related to managing a network
VLANs provide effective measures for controlling changes and reducing costsUsers in a VLAN can share the same network address space i.e. IP subnetVLANs require less rewiring, configuration and debugging
Movement of Users
VLANs Help Control Broadcast Activity
Most effective measures is to properly segment with firewalls that help prevent problems on segment from damaging other parts of the networkFirewall segmentation provides reliability and minimizes overhead broadcast trafficIf no routers are placed between switches, broadcasts (layer 2) are sent to every switched port – referred to as a FLAT network(one broadcast domain across the whole network)Flat Network– Provides low latency & high throughput– Easy to administer
VLANs Controlling Broadcast Activity
FLAT Network – Disadvantages– Increases vulnerability to broadcast traffic across all switches,
ports, backbone links and usersVLANs effectively extend firewalls from routers to the switch fabric and protecting against potentially dangerous broadcast problemsCreating firewalls– Assign switch ports or users to specific VLAN groups both
within single switches and across multiple connected switches
VLANs and Broadcast Activity
How do VLANs Improve Network Security
Restrict number of users in a VLAN groupPrevent another user from joining without first receiving approval from the VLAN network management applicationConfigure all unused ports to a default low-service VLAN
Tightening Network Security
VLANS Save Money
Connect existing HUBS to switchesEach hub segment connected to a switch can be assigned only ONE VLANStations that share a hub segment are in the same VLANIf a station need to be assigned a new VLAN that station must move to the new hub with the appropriate VLAN
Using Existing Hubs
Summary
Switch is designed to physically segment a LAN into individual domainsA typical LAN is configured according to the physical infrastructure it connectsLANs that use LAN switching devices - VLAN technology is cost effective and an efficient way of grouping network users into virtual workgroups regardless of their physical placement
Summary Continued
VLANs work at Layer 2 and Layer 3 of the OSIVLAN architecture must allow transportation of VLAN information between interconnected switches and routers on the corporate backboneMost common approach for logically grouping users into distinct VLANS are frame filtering and frame tagging
Summary Continued
Types of VLANS– Port-centric– Static– Dynamic
VLANs provide benefits– Reduce administration costs – moves, additions changes– Controlled broadcast activity– Workgroup and network security– Save money by using existing hubs