VLANSuman Pandey

ReferencesD. Passmore, and J. Freeman, The Virtual LAN Technology Report, http://www.3com.com/nsc/200374.html, March, 1997IEEE 802.1Q, IEEE Standard for Local and Metropolitan Area Networks: Virtual Bridge Local Area Networks, 1998 Meng Guo , Subrata Mazumdar , Discovery of Spanning Trees in Virtual Bridged LAN , The Quarterly Newsletter of SNMP Technology, Comment, and Events, Volume 9, Number 1, December, 2001

OutlineGeneral Concepts of VLANWhat is VLAN ?Why use VLAN's?Different way to assign VLAN Membership.Spanning Tree in VLANFrame processing and 802.1Q standardDifferent kind of logical VLAN architectureImplementation Details of VLAN for Topology DiscoveryDifferent Vendor specific SolutionsSPECTRUM VLAN manager implementationMIB used

General Concepts of VLANPaper: The Virtual LAN Technology Report

What is VLAN ?vendor-specific solution and strategy, so defining it is an issue.VLAN's allow a network manager to logically segment a LAN into different broadcast domains.multiple physical LAN segments independent of physical location and can communicate as if they were on a common LAN

Why use VLAN's? Performance Formation of Virtual Workgroups Simplified Administration Reduced Cost Security

VLAN MembershipMembership by Port Membership by MAC AddressMembership by IP Subnet Address

portvlan11213241

disadvantage of this method is that it does not allow for user mobility.

VLAN MembershipMembership by Port Membership by MAC AddressMembership by IP Subnet AddressAdvantage : no reconfiguration needed Disadvantage : VLAN membership must be assigned initially. performance degradation as members of different VLANs coexist on a single switch port

MAC Address vlan1212354145121 12389234873743 13045834758445 25483573475843 1

VLAN MembershipMembership by Port Membership by MAC AddressMembership by IP Subnet Address Advantage: Good for application-based VLAN strategyUser can move workstationseliminate the need for frame taggingDisadvantage :Performance/ looking for L3 address in packet.Less effective with protocols such as IPX, DECnet, or AppleTalkunroutable protocols such as NetBIOS

IP Subnet vlan23.2.24 126.21.35 2

Frame Processing in VLAN envRole of Bridgesbridge on receiving data determines to which VLAN the data belongs either by implicit or explicit tagging [802.1Q].The bridge also keeps track of VLAN members in a filtering database which it uses to determine where the data is to be sent all the bridges in the VLAN should contain the same information in their respective filtering databases

Active Topology of Network with Bridges

Filtering DatabaseMembership information for a VLAN is stored in a filtering database Static Entries Static Filtering Entries: for every port whether frames to be sent to a specific MAC address or group address and on a specific VLAN should be forwarded or discarded, or follow dynamic entryStatic Registration Entries: whether frames to be sent to a specific VLAN are to be tagged or untagged and which ports are registered for that VLAN Dynamic Entries (learnt by bridges)Dynamic Filtering Entries: Group Registration Entries: follows GVRP protocol.Dynamic Registration Entries:

Tagging [802.1Q] Ethernet Frame Tag Header:

Token Ring and Fiber Distributed Data Interface (FDDI) tag header:

TCI

VLAN architecture going forwardInfrastructural VLANService-Based VLAN

Other Details of the ReportDHCP with VLANATM with VLANVLAN Migration StrategyAutomatic configuration of VLAN

Implementation Details of VLAN for Topology DiscoveryPaper: Discovery of Spanning Trees in Virtual Bridged LAN

Different Vendor specific SolutionsAvaya's VLANMaster application - only works with Avayas Cajun switches. Aprisma's SPECTRUM VLAN Manager It uses the Cabletron Discovery Protocol (CDP) to find all CDP compatible 802.1Q switches in a domainCisco's VlanDirector uses Cisco Discovery Protocol (CDP) VlanDirector cannot manage any devices that do not run CDP. 3COM's Enterprise VLAN Manager Granite open source C API/SDK to provision VLAN configurations using SNMP for Riverstone products.

MIB InformationMIB used RFC1213-MIB BRIDGE-MIB (RFC 1493)Q-BRIDGE-MIB (RFC 2674).Bridge MIB Useddot1dStpPort dot1qPvid dot1dStpPortState dot1dStpPortDesignatedRoot dot1dStpPortDesignatedBridge dot1dStpPortDesignatedPort

Discovery of Spanning Trees and VLANs

StepsDeduce the target Virtual Bridged LAN from an arbitrary IP address in the Virtual Bridged LAN Automatically discover all the bridges in the target Virtual Bridged LANCollect spanning tree and VLAN related MIB variables from the discovered brides using SNMP Construct the spanning trees in the Virtual Bridged LAN and associate the spanning trees with VLANs.

Implementation Detail They have used Avaya's Cajun switches, and the STP is stored in PROMINET-MIBCollecting Spanning Tree Related Information 12

Implementation Detail Construction of Per-VLAN Spanning Tree Spanning Tree of VLAN 1234