VLAN Suman Pandey

References D. Passmore, and J. Freeman, “The Virtual LAN Technology Report”, March, 1997 IEEE 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

Outline General Concepts of VLAN –What is VLAN ? –Why use VLAN's? –Different way to assign VLAN Membership. –Spanning Tree in VLAN –Frame processing and 802.1Q standard –Different kind of logical VLAN architecture Implementation Details of VLAN for Topology Discovery –Different Vendor specific Solutions –SPECTRUM VLAN manager implementation –MIB used

General Concepts of VLAN Paper: 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 Membership Membership by Port Membership by MAC Address Membership by IP Subnet Address portvlan disadvantage of this method is that it does not allow for user mobility.

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

VLAN Membership Membership by Port Membership by MAC Address Membership by IP Subnet Address IP Subnetvlan Advantage: Good for application-based VLAN strategy User can move workstations eliminate the need for frame tagging Disadvantage : Performance/ looking for L3 address in packet. Less effective with protocols such as IPX™, DECnet®, or AppleTalk® “unroutable” protocols such as NetBIOS

Frame Processing in VLAN env Role of Bridges bridge 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 Database Membership 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 entry Static 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 forward Infrastructural VLANService-Based VLAN

Other Details of the Report DHCP with VLAN ATM with VLAN VLAN Migration Strategy Automatic configuration of VLAN

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

Different Vendor specific Solutions Avaya's VLANMaster application - only works with Avaya’s Cajun switches. Aprisma's SPECTRUM VLAN Manager It uses the Cabletron Discovery Protocol (CDP) to find all CDP compatible 802.1Q switches in a domain Cisco'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 Information MIB used RFC1213-MIB BRIDGE-MIB (RFC 1493)RFC 1493 Q-BRIDGE-MIB (RFC 2674).RFC 2674 Bridge MIB Used dot1dStpPort dot1qPvid dot1dStpPortState dot1dStpPortDesignatedRoot dot1dStpPortDesignatedBridge dot1dStpPortDesignatedPort

Discovery of Spanning Trees and VLANs Steps Deduce 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 LAN Collect 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-MIB Collecting Spanning Tree Related Information 1 2

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