© 1999, Cisco Systems, Inc. Module 9: Understanding Virtual LANs

9-2 CSE: Networking Fundamentals—VLANs © 1999, Cisco Systems, Inc. Agenda What Is a VLAN? How Does it Work? VLAN Technologies

9-3 CSE: Networking Fundamentals—VLANs © 1999, Cisco Systems, Inc. Constraints of Shared LANs Users are physically bound Subnets are tied to hubs Users are grouped by location No security on segment Addressing is constrained Moves require address changes Router ports are expensive

9-4 CSE: Networking Fundamentals—VLANs © 1999, Cisco Systems, Inc. Virtual LANs One broadcast domain within a switch VLANs help manage broadcast domain Can be defined on port groups, users, or protocols LAN switches and network management software provide a mechanism to create VLANs Server Farm VLAN 1 VLAN 2 VLAN 3

9-5 CSE: Networking Fundamentals—VLANs © 1999, Cisco Systems, Inc. Remove the Physical Boundaries Group users by department, team, or application Routers provide communication between VLANs EngineeringMarketingAcctg. Floor 3 Floor 2 Floor 1

9-6 CSE: Networking Fundamentals—VLANs © 1999, Cisco Systems, Inc. VLAN Benefits Reduced administrative costs –Simplify moves, adds, and changes Efficient bandwidth utilization –Better control of broadcasts Improved network security –Separate VLAN group for high-security users –Relocate servers into secured locations Scalability and performance –Microsegment with scalability –Distribute traffic load

9-7 CSE: Networking Fundamentals—VLANs © 1999, Cisco Systems, Inc. VLAN Components Switches, Routers, Servers, Management Membership Establishment Inter-VLAN Communications Communication Across Fabric Centralized Administration Switches—Membership determination Trunking—Common VLAN exchange Multiprotocol routing— Inter-VLAN exchange Servers—Multi-VLAN communication Management—Security, control, administration Server Communication

9-8 CSE: Networking Fundamentals—VLANs © 1999, Cisco Systems, Inc. Approaches Can Vary Performance Port-Based VLAN 1 VLAN 2 VLAN 3 Layer 3-Based Subnet xx VLAN 1VLAN 2 Subnet xx VLAN 2 MAC-Based VLAN 1 MAC Addresses Establishing VLAN Membership Port driven MAC address driven Network address driven Application type driven

9-9 CSE: Networking Fundamentals—VLANs © 1999, Cisco Systems, Inc. Membership by Port VLAN 2VLAN 1 VLAN 3 Maximizes Forwarding Performance Users assigned by port association Requires no lookup if done in ASICs Easily administered via GUIs Maximizes security between VLANs Packets do not “leak” into other domains Easily controlled across network

9-10 CSE: Networking Fundamentals—VLANs © 1999, Cisco Systems, Inc. Requires Filtering, Impacts Performance Membership by MAC Addresses VLAN A3EF1A OA032192FA2A GA3A VLAN G4GF2A THTB3A GGGF3A VLAN A3EF1A OA032192FA2A GA3A VLAN G4GF2A THTB3A GGGF3A Table Exchange Tables Add Administration Overhead Users assigned based on MAC addresses Flexible, yet adds overhead Impacts performance, scalability, administration Similar process for higher layers MAC Address Tables MAC Address Tables

9-11 CSE: Networking Fundamentals—VLANs © 1999, Cisco Systems, Inc. Multiple VLANs per Port Broadcast Outgoing Mac 1 Mac 2 Mac 3 Mac 4 Mac 5 Mac 6 Mac 7 Mac 8 Mac 9 Mac 10 Mac 11 Mac 12 Broadcast Incoming Does This Make Sense in Switched/Shared LANs? Requested when multiple clients are attached Requires address lookups Cannot filter broadcasts on shared segment Results in lots of administration, little return Hub

9-12 CSE: Networking Fundamentals—VLANs © 1999, Cisco Systems, Inc. Two Physical Topology Approaches Communicating Between VLANs Layer 3 links VLANs together Adds additional security and management Logical links conserve physical ports Multimode, depending on protocol Controls access by VLAN Up to 255 VLANs per router VLAN 2 VLAN 3 VLAN 1 Cisco Internetworking Software VLANs 1, 2, 3 Logical Communication Physical Link per VLAN

9-13 CSE: Networking Fundamentals—VLANs © 1999, Cisco Systems, Inc. Server Connectivity Intelligent NICs decode tagging Supported by industry (Intel, CrossPoint) Maximizes performance, flexibility C5000 C2900 C5000 C2820 Cisco 7500 VLAN 1 VLAN 2 VLAN 3 Server Farm Multiple Tagging to Each Server

© 1999, Cisco Systems, Inc. © 1999, Cisco Systems, Inc. VLAN Technologies

9-15 CSE: Networking Fundamentals—VLANs © 1999, Cisco Systems, Inc. Inter-Switch Link VLAN Tag Added at Incoming Port VLAN Tag Stripped by Forwarding Port Inter-Switch Link (ISL) Carries VLAN Identifier Interconnects multiple switches and maintains VLAN information as traffic goes between switches Establishes membership through ASICs Labels each packet as received (“packet tagging”) Eliminates lookups and tables Transports multiple VLANs across links Protocol, endstation- independent Easily managed ISLISL 802.1Q LANE

9-16 CSE: Networking Fundamentals—VLANs © 1999, Cisco Systems, Inc. Wide vendor endorsement for 802.1Q tagging standard Cisco supports across Fast Ethernet, Gigabit uplinks Cisco maps ISL to 802.1Q dynamically with VTP Packet Tagging as Common VLAN Exchange VLAN Standardization Level-1 Explicit Tagging SRC DESSRC Data DES SRC FCS FCS DESSRCFCS VLAN ID

9-17 CSE: Networking Fundamentals—VLANs © 1999, Cisco Systems, Inc Q VLAN Standard Implementation Cisco environment uses ISL Vendor environment uses an existing, yet different packet tagging method Interdomain communication based on 802.1Q standard Si Cisco Domain Vendor X Domain ISL ? Company ABC Typical Environment

9-18 CSE: Networking Fundamentals—VLANs © 1999, Cisco Systems, Inc. VLAN administration and configuration protocol –Reduces VLAN setup and administration –Eliminates configuration errors –Decreases network manager’s time adding and managing VLANs –Maps VLANs across different backbones (FDDI, Fast Ethernet, ATM) –Maps between ISL and 802.1q –Maintains security between VLANs Virtual Trunk Protocol (VTP) ATM Fabric VLAN 2 VLAN 1 ISL LANE ISL LANE 802.1Q

9-19 CSE: Networking Fundamentals—VLANs © 1999, Cisco Systems, Inc. Summary VLANs enable logical (instead of physical) groups of users on a switch VLANs address the needs for mobility and flexibility VLANs reduce administrative overhead, improve security, and provide more efficient bandwidth utilization

20Presentation_ID © 1999, Cisco Systems, Inc.