1 RST _05_2001_c1 © 2001, Cisco Systems, Inc. All rights reserved. LAN Protocols Bill Dufresne SE-IV Cisco Systems CCIE, Content/Video Specialist

RST _05_2001_c1 © 2001, Cisco Systems, Inc. All rights reserved Complexity “Just-in-Time” Networking! Familiar LAN Design? Network Protocols Are Important— But Just One Piece of the Puzzle

RST _05_2001_c1 © 2001, Cisco Systems, Inc. All rights reserved So…What Makes for a Solid LAN? Three simple ingredients: 1. Well thought-out network design 2. Complimentary suite of protocols 3. Strategic application of protocols Strategic Application of Protocols and Features Requires Detailed Knowledge

RST _05_2001_c1 © 2001, Cisco Systems, Inc. All rights reserved Domain What? Collision domain It’s my turn, OK it’s now your turn Broadcast domain Attention world, I have something to say Failure domain Making one’s problem everyone’s problem Spanning Tree domain How long to converge? Policy domain Regional policing of the network Intelligence domain Value-added Services; the router does what?

RST _05_2001_c1 © 2001, Cisco Systems, Inc. All rights reserved LAN Domains Described Basic LAN Router/Layer-3 Switch Collision Domain Broadcast Domain Failure Domain STP Domain Policy Domain Intelligence Domain

RST _05_2001_c1 © 2001, Cisco Systems, Inc. All rights reserved Large Campus Design Distribution Layer 3 Distribution Layer 3 Core Layer 2/3 Core Layer 2/3 Access Layer 2 Access Layer 2 Server Farm A Building ABuilding B Sample Design A: Large Campus Design

RST _05_2001_c1 © 2001, Cisco Systems, Inc. All rights reserved UniDirectional Link Detection (UDLD) What is UDLD? Detects one-way connectivity Independent of auto-negotiation Similar to FEFI* in 100Fx Supports 10/100Tx, 1000X *FEFI: Far End Fault Indication MS S A A UDLD TX RX TX RX TX RX TX RX TX RX

RST _05_2001_c1 © 2001, Cisco Systems, Inc. All rights reserved Spanning Tree 802.1d Loop-free Connectivity X X A Switch Is Elected As Root F F F F F F F B B F F F A ‘Tree-like’ Loop-free Topology Is Established F F A Root B MS S A A

RST _05_2001_c1 © 2001, Cisco Systems, Inc. All rights reserved Typical Spanning Tree Layout Several enhancements specifically targeted to ‘triangular’ topology STP enhancements Quicker convergence Greater stability Load balancing Root F F F F F F F F F F X X BB MS S A A

RST _05_2001_c1 © 2001, Cisco Systems, Inc. All rights reserved. 10 © 2001, Cisco Systems, Inc. All rights reserved. 10 © 2001, Cisco Systems, Inc. All rights reserved. 10 Default Spanning Tree Timers Hello 2 seconds (minute 1) Forward delay 15 seconds (minute 4) Maximum age 20 seconds (minute 6) Time Blocking 20 Sec Listening Learning 15 Sec Forwarding Max–Age Pre-Forwarding 1 Pre-Forwarding 2 15 Sec IEEE 802.1D Defaults MS S A A

RST _05_2001_c1 © 2001, Cisco Systems, Inc. All rights reserved. 11 © 2001, Cisco Systems, Inc. All rights reserved. 11 © 2001, Cisco Systems, Inc. All rights reserved. 11 Event #1—New node Default is 30 seconds for STP to ensure loop-free connection Event #2—Uplink failure Default is 30 seconds for STP to find alternate path Event #3—Indirect failure Default is 50 seconds for STP to find alternate path Quicker STP Convergence Root F F FF F BB X X Barb: Made ‘X’ red, as with previous graphic Barb: Made ‘X’ red, as with previous graphic MS S A A

RST _05_2001_c1 © 2001, Cisco Systems, Inc. All rights reserved. 12 © 2001, Cisco Systems, Inc. All rights reserved. 12 © 2001, Cisco Systems, Inc. All rights reserved. 12 PortFast Spanning tree enhancement to reduce convergence time Used for ports connected to hosts that cannot possibly cause a loop Bypasses ‘listening’ and ‘learning’ stages of STP Reduces connection time to 2-3 seconds from 30 seconds Root F F F F F F F F F F BB 1 1 F F F F F F F F F F BB 1 1 MS S A A

RST _05_2001_c1 © 2001, Cisco Systems, Inc. All rights reserved. 13 © 2001, Cisco Systems, Inc. All rights reserved. 13 © 2001, Cisco Systems, Inc. All rights reserved w Spanning tree enhancement to reduce fail-over convergence time Used when recovery path is known and predictable Bypasses ‘listening’ and ‘learning’ stages of STP Reduces fail-over time to 2–3 seconds from 30 seconds Auto-populates upstream address tables 2 2 Root F F F F F F F F F F BB 1 1 F F F F F F F F F F BB 1 1 MS S A A

RST _05_2001_c1 © 2001, Cisco Systems, Inc. All rights reserved. 14 © 2001, Cisco Systems, Inc. All rights reserved. 14 © 2001, Cisco Systems, Inc. All rights reserved. 14 ? X X VLAN Trunking Most common topologies consist of multiple VLANs Problem becomes one of how to carry multiple VLANs worth of traffic while maintaining isolation Multiple protocols to solve the problem M A S S S

RST _05_2001_c1 © 2001, Cisco Systems, Inc. All rights reserved. 15 © 2001, Cisco Systems, Inc. All rights reserved. 15 © 2001, Cisco Systems, Inc. All rights reserved. 15 VLAN Tag Added by Incoming Port VLAN Tagging Protocols ISL 802.1Q (FDDI) LANE (ATM) Which Tag and Which Protocol? Which Tag and Which Protocol? M A S S S

RST _05_2001_c1 © 2001, Cisco Systems, Inc. All rights reserved. 16 © 2001, Cisco Systems, Inc. All rights reserved. 16 © 2001, Cisco Systems, Inc. All rights reserved. 16 MAC Length/Type MAC DATA PAD FCS Used in: IEEE 802.3ac IEEE 802.1Q IEEE 802.1p VID (VLAN ID)—12 Bits Q Tagging Scheme Tag Control Information User Priority User Priority CFI Destination Address Source Address EtherType = TPID M A S S S

RST _05_2001_c1 © 2001, Cisco Systems, Inc. All rights reserved. 17 © 2001, Cisco Systems, Inc. All rights reserved. 17 © 2001, Cisco Systems, Inc. All rights reserved. 17 Spanning Tree Issues 802.1Q specifies one spanning tree (STP) per bridge cloud, but it does not preclude multiple spanning trees One spanning tree doesn’t allow for load-sharing M A S S S

RST _05_2001_c1 © 2001, Cisco Systems, Inc. All rights reserved. 18 © 2001, Cisco Systems, Inc. All rights reserved. 18 © 2001, Cisco Systems, Inc. All rights reserved. 18 Growing Number of Spanning Trees PVST (Per VLAN STP) One active topology per VLAN (ISL or 802.1Q) Only 2 unique topologies CPU consumed to maintain 4 topologies Finite limit to number of trunks and VLANs B B B B ? VLAN 10 VLAN 20 VLAN 30 VLAN 40 B B B B M A S S S

RST _05_2001_c1 © 2001, Cisco Systems, Inc. All rights reserved. 19 © 2001, Cisco Systems, Inc. All rights reserved. 19 © 2001, Cisco Systems, Inc. All rights reserved. 19 Multiple Instance Spanning Tree (MIST) Separates STP topologies from VLANs Map VLANs to topologies Must run on all switches Similar to 802.1s efforts (SSTP*) Pseudo-compatible with non-Cisco switches Cannot run with PVST(+) Virtual BPDU count scales near 80,000! *SSTP: Shared Spanning Tree Protocol M A S S S

RST _05_2001_c1 © 2001, Cisco Systems, Inc. All rights reserved. 20 © 2001, Cisco Systems, Inc. All rights reserved. 20 © 2001, Cisco Systems, Inc. All rights reserved. 20 B B B B ? MIST Function Two active topologies All VLANs mapped to one of two topologies Lower BPDU counts Simpler implementation BPDUs are not encapsulated in VLAN tag BPDUs appear as multicasts to non-MIST environment B B VLAN 10 VLAN 20 VLAN 30 VLAN 40 M A S S S

RST _05_2001_c1 © 2001, Cisco Systems, Inc. All rights reserved. 21 © 2001, Cisco Systems, Inc. All rights reserved. 21 © 2001, Cisco Systems, Inc. All rights reserved. 21 VLAN A VLAN B Root B B B B MIST (802.1s) Load Balancing Per-VLAN-Spanning-Tree Load balancing at Layer 2 Alternate ‘root’ switches Fast fail-over with UplinkFast Use following command: set spantree root *MIST: Multiple Instance Spanning Tree Root MS S A A

RST _05_2001_c1 © 2001, Cisco Systems, Inc. All rights reserved. 22 © 2001, Cisco Systems, Inc. All rights reserved. 22 © 2001, Cisco Systems, Inc. All rights reserved. 22 EtherChannel 802.3af Load sharing and redundancy provided Valid link aggregations include 2, 4, and 8 links AB EtherChannel 100/1000 Ethernet 7 100/1000 Ethernet 3 100/1000 Ethernet 5 100/1000 Ethernet 6 100/1000 Ethernet 2 100/1000 Ethernet 1 100/1000 Ethernet 4 100/1000 Ethernet 8

RST _05_2001_c1 © 2001, Cisco Systems, Inc. All rights reserved. 23 © 2001, Cisco Systems, Inc. All rights reserved. 23 © 2001, Cisco Systems, Inc. All rights reserved af Load Balancing How does it load share? Layer 2 devices Source/destination MAC Layer 3 devices Source/destination IP Server NICs Source/destination MAC Layer 3 Switch or Router Layer 2 Switch Server A A S SM S

24 RST _05_2001_c1 © 2001, Cisco Systems, Inc. All rights reserved.