VLAN

1
VLAN

• Suman Pandey

2
References

• D. Passmore, and J. Freeman, The Virtual LAN
  Technology Report, http//www.3com.com/nsc/200374
  .html, 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

3
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

4
General Concepts of VLAN

• Paper The Virtual LAN Technology Report

5
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

6
Why use VLAN's?

• Performance
• Formation of Virtual Workgroups
• Simplified Administration
• Reduced Cost
• Security

7
VLAN Membership

• Membership by Port
• Membership by MAC Address
• Membership by IP Subnet Address

8
VLAN Membership

• Membership by Port
• Membership by MAC Address
• Membership by IP Subnet Address

• Advantage
• no reconfiguration needed
• Disadvantage
• VLAN membership must be assigned initially.
• performance degradation as members of different
  VLANs coexist on a single switch port

9
VLAN Membership

• Membership by Port
• Membership by MAC Address
• Membership by IP Subnet Address

• 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

10
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

11
Active Topology of Network with Bridges
12
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

13
Tagging 802.1Q

• Ethernet Frame Tag Header
• Token Ring and Fiber Distributed Data Interface
  (FDDI) tag header
• TCI

14
VLAN architecture going forward
Infrastructural VLAN
Service-Based VLAN
15
Other Details of the Report

• DHCP with VLAN
• ATM with VLAN
• VLAN Migration Strategy
• Automatic configuration of VLAN

16
Implementation Details of VLAN for Topology
Discovery

• Paper Discovery of Spanning Trees in Virtual
  Bridged LAN

17
Different Vendor specific Solutions

• Avaya'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 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.

18
MIB Information

• MIB used
• RFC1213-MIB
• BRIDGE-MIB (RFC 1493)
• Q-BRIDGE-MIB (RFC 2674).
• Bridge MIB Used
• dot1dStpPort
• dot1qPvid
• dot1dStpPortState
• dot1dStpPortDesignatedRoot
• dot1dStpPortDesignatedBridge
• dot1dStpPortDesignatedPort

19
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.

20
Implementation Detail
1
2
They have used Avaya's Cajun switches, and the
STP is stored in PROMINET-MIB
Collecting Spanning Tree Related Information
21
Implementation Detail
3
4
Construction of Per-VLAN Spanning Tree
Spanning Tree of VLAN 12
22
(No Transcript)