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1© 1999, Cisco Systems, Inc. 5050911_04F9_c3
HighHigh--AvailabilityAvailabilityEnterprise NetworkEnterprise Network
DesignDesign
[email protected]@cisco.com
25050911_04F9_c3 © 1999, Cisco Systems, Inc.
Staying On TargetStaying On TargetHA Focus HA Focus vs vs Distractions!Distractions!
“Flat networksare easier”beware!
Five nines is job one!
Inherited complexityhard to purge
The latest cool stuffolder is more stable
“Variety” of vendors, protocols, designs, etc.
“Featurerich”let’s use all the knobs!
Change is hard, sometimes $$$
35050911_04F9_c3 © 1999, Cisco Systems, Inc.
HA Features of the Catalyst 6500HA Features of the Catalyst 6500Consider for Backbones & Server FarmsConsider for Backbones & Server Farms
✔ Fabric Redundancyswitch fabric modulein CatOS 6.1
✔ Supervisor RedundancyHA feature in CatOS 5.4.1stateful recoveryimage versioning on the fly
✔ MSFC Redundancyconfig-sync featureIOS 12.1.3 CatOS 6.1HSRP pair
45050911_04F9_c3 © 1999, Cisco Systems, Inc.
Thinking Outside the BoxThinking Outside the Box
For HA/HP design “outside the box”
☛ the logical design is critical☛ network features & protocols☛ geophysical diversity is powerful
Inside: “HA”, RAID, UPS, MTBF, etc.
55050911_04F9_c3 © 1999, Cisco Systems, Inc.
Dramatis Dramatis PersonaePersonaeOur Cast of SymbolsOur Cast of Symbols
✔ Links GE, DPT, SONET, etc.
✔ L2 switchingL2 forwarding in hardware
✔ L3 switchingL3/L2 forwarding in hardware
✔ Routing L3 forwarding (SW or HW)
✔ Control plane = IOS routing protocols & features
✔ QoS where required✔ Application intelligence
Catalyst 4000
Cisco 7500 Cisco 12000
Catalyst 6500
GigE Channel
65050911_04F9_c3 © 1999, Cisco Systems, Inc.
Client Blocks
Distribution L3
Access L2
HA Gigabit Campus Architecturesurvivable modules + survivable backbone
Backbone
ServerBlock
Server Farm
Distribution L3
Access L2E or FE PortGE or GEC
Ethernet or ATMLayer 2 or Layer 3
☛ Define the missioncritical parts first!
75050911_04F9_c3 © 1999, Cisco Systems, Inc.
High Availability DesignHigh Availability DesignWhy aWhy a Modular ABC ApproachModular ABC Approach
✔ Many new products, features, technologies
✔ HA and HP application operation is the goal
✔ Start with modular, structured approach (the “logical” design)
✔ Add multicast, VoIP, DPT, DWDM...
85050911_04F9_c3 © 1999, Cisco Systems, Inc.
Price per 10/100
Catalyst 2912GCatalyst 2948GCatalyst 2980G
242410/100 Ports10/100 PortsGigabit PortsGigabit Ports
24-500+24-500+ 24-350+24-350+3-38+3-38+ 8-64+8-64+
Catalyst 5XXX
32-9632-966-126-12
Catalyst 4XXX
$100
$200
$250
$300
$350
Switching CapacitySwitching Capacity Up to 72 MppsUp to 72 Mpps20 Mpps20 Mpps Up to 150 MppsUp to 150 MppsBackplaneBackplane 24 Gbps24 Gbps 1.2-3.6 + 10Gbps1.2-3.6 + 10Gbps 250+ Gbps250+ Gbps
NewNew
NewNew
New New ModulesModules
Catalyst 6XXX
Design the SolutionDesign the SolutionThen Pick the ProductsThen Pick the Products
New New ModulesModules
95050911_04F9_c3 © 1999, Cisco Systems, Inc.
HA Design Reality Check!HA Design Reality Check!Assume Things Fail Assume Things Fail -- Then What?Then What?
✔ Networks are complex✔ Things break, people make mistakes✔ What happens if a failure occurs?✔ Simple, structured, deterministic design
required for fast recovery✔ The “tradeoffs”
your choices are important
105050911_04F9_c3 © 1999, Cisco Systems, Inc.
Layer 2Layer 2
Layer 2Layer 2AccessAccess
DistributionDistribution
BuildingBuilding
Core L3Core L3
ServerServerDistributionDistribution
Server FarmServer Farm
Layer 3Layer 3
3
2
1
5
6
BranchesBranches
WAN
WANbackup
4
Network RecoveryNetwork RecoveryHow Long? What Happens?How Long? What Happens?
115050911_04F9_c3 © 1999, Cisco Systems, Inc.
Failure ScenarioFailure
Scenario
1,2 server
3,4 uplink
5,6 core
dual-path L3
EtherChannel
L3 routing
L2 general
DPT
1,2 server
3,4 uplink
5,6 core
dual-path L3
EtherChannel
L3 routing
L2 general
DPT
RecoveryMode
RecoveryMode
RecoveryTime
RecoveryTime
Server NIC
HSRP (& UplinkFast)
HSRP track
alternate path used
channel recovery
EIGRP or OSPF
L2 spanning tree
IPS
Server NIC
HSRP (& UplinkFast)
HSRP track
alternate path used
channel recovery
EIGRP or OSPF
L2 spanning tree
IPS
< 2 seconds
tune to 3 seconds
tune to 3 seconds
< 2 seconds
< 1 second
depends on tuning
tune (up to 50 seconds)
50 milliseconds
< 2 seconds
tune to 3 seconds
tune to 3 seconds
< 2 seconds
< 1 second
depends on tuning
tune (up to 50 seconds)
50 milliseconds
Network Recovery TimesNetwork Recovery TimesIf You Follow the RulesIf You Follow the Rules
125050911_04F9_c3 © 1999, Cisco Systems, Inc.
Design for High AvailabilityDesign for High AvailabilityHow to Build Boring Networks!How to Build Boring Networks!
✔ The Concepts✔ The Rules✔ Design Building Block✔ Design Backbone✔ Notes on Tuning
135050911_04F9_c3 © 1999, Cisco Systems, Inc.
HA Network Design ConceptsHA Network Design Conceptsthinking outside the boxthinking outside the box
1) Simplicity & Determinism2) Collapse the Sandwich3) Spanning Tree Failure Domain4) Map L3 to L2 to L15) Scaling and Hierarchy6) ABCs of Module + Backbone
Design7) The Four Corners
145050911_04F9_c3 © 1999, Cisco Systems, Inc.
1) Simplicity and Determinism1) Simplicity and Determinismreducing the degrees of freedomreducing the degrees of freedom
✔ Every Choice Affects Availability!✔ Determinism or Flexibility?✔ Would you support 27 desktop environments?✔ Would you support 13 network vendors?✔ Would you use 57 varieties of Cisco IOS?
FlexibleComplexVaried
SimpleStructuredDeterministic “HA Continuum”
Boring! Interesting!
155050911_04F9_c3 © 1999, Cisco Systems, Inc.
TraditionalModel
Fiber
SONET
Big Fat Pipe
• Lower equipment cost• Lower operational cost• Simplified architecture• Scalable capacity
Optical Internetworking
Fiber
IP
FR/ATM
IP
2)2) Collapse the SandwichCollapse the Sandwichroute IP over glassroute IP over glass
Service
Traffic Eng
Fiber Mgmt
165050911_04F9_c3 © 1999, Cisco Systems, Inc.
33)) Minimize the Failure DomainMinimize the Failure Domainpublic enemy number onepublic enemy number one
Where should root go?
What happens when something breaks?
How long to converge?
Many blocking links
Large failure domain!
Broadcast flooding
Multicast flooding
Loops within loops
ST from heck
Times 100 VLANs?
avoid highly meshed, non-deterministic large scale L2 = VLAN topology
Building 1 Building 2
Building 3 Building 4
175050911_04F9_c3 © 1999, Cisco Systems, Inc.
4)4) Map L3 to L2 to L1Map L3 to L2 to L1
✔ Easier administration & troubleshooting
Clients in subnet 10.0.55.0
VLAN 55
wiring closet “55” on floor 55
access switch “55”
interface VLAN 55
all match and life is good
go fishing with your kids
10/100 BaseT
GE or GEC
185050911_04F9_c3 © 1999, Cisco Systems, Inc.
5) Scaling and Hierarchy5) Scaling and Hierarchy
Strong hierarchies like telephone system and Internet segment addressing and therefore scale
U
C
N
U
C
N
U
C
N
C complexityU unmanageableN number of devices
Flat L2 Ethernet is easy but does not scale
ATM LANE is logically flat, scales as N squared
195050911_04F9_c3 © 1999, Cisco Systems, Inc.
6)6) Building Block &Building Block &Backbone Design ABCsBackbone Design ABCs
WAN
EcommerceSolution
PSTN
DistributionDistribution
CoreCore
LAN AccessLAN Access
DistributionDistribution
Server Farm
Internet
A design bb
B design BB
C connect bb to BB
Divide and conquer
Cookie cutter configuration
Deterministic
L3 demarcation
WAN AccessWAN Access
205050911_04F9_c3 © 1999, Cisco Systems, Inc.
7) Four Square Network Redundancy7) Four Square Network Redundancyor the Four Corners Problemor the Four Corners Problem
One ChassisOne Chassis Two ChassisTwo Chassis
One One SupervisorSupervisor
Two Two SupervisorsSupervisors
SimplestSimplestNo RedundancyNo Redundancy
Most ComplexMost ComplexBelt and SuspendersBelt and Suspenders
GeoPhysicalGeoPhysicalEffectiveEffective
When space When space is limitedis limited
“HA”“HA”
L3L3
215050911_04F9_c3 © 1999, Cisco Systems, Inc.
Dos and Don’ts for HA DesignDos and Don’ts for HA Design
1) Eliminate STP Loops2) L3 Dual-Path Design3) EtherChannel Across Cards4) Workgroup Servers5) Use HSRP Track6) Passive Interfaces7) Issues with Single-Path Design8) Oversubscription Guidelines9) HA for single attached servers10) Protocol Tradeoffs11) UDLD Protection
225050911_04F9_c3 © 1999, Cisco Systems, Inc.
Rule 1) Eliminate STP LoopsRule 1) Eliminate STP Loopsin the backbone and mission critical pointsin the backbone and mission critical points
No blocking links to waste bandwidth
Avoids slow STP convergence
Very deterministic
Routed links not VLAN trunks
L2 Gigabit switch in backbone
subnet X = VLAN X
Too many cooks spoil the brothL3 control is better
X.2 X.3X.1
Root VLAN X
235050911_04F9_c3 © 1999, Cisco Systems, Inc.
Rule 2) Dual EqualRule 2) Dual Equal--Cost Path L3Cost Path L3
✔ Load balance - don’t waste bandwidthunlike L1 and L2 redundancy
✔ Fast recovery to remaining pathdetect L1 down & purge - about 1s
✔ Works with any routed fat pipes
Path A
Path B
Destination network X
Equal cost routes to XPath APath B
245050911_04F9_c3 © 1999, Cisco Systems, Inc.
Rule 3) Rule 3) EtherChannel EtherChannel Across CardsAcross Cards
Increased availability✔ Sub second recovery✔ Spans cards on 6500✔ Up to 8 ports in channel
Small complexity increase✔ Single L2 STP link✔ Single L3 subnet✔ less if channel set “on”
255050911_04F9_c3 © 1999, Cisco Systems, Inc.
Rule 4a) Connect Workgroup ServerRule 4a) Connect Workgroup Server�With no L2 recovery path, what happens if link
breaks ….
Workgroup server X.100attached to distribution layerL2 path to client X.1
Client X.1 VLAN X in purple includes clients and workgroup servers attached at different places.
A B
C
Links to core
Link CB breaks ….
265050911_04F9_c3 © 1999, Cisco Systems, Inc.
Rule 4b) Connect Workgroup ServerRule 4b) Connect Workgroup Server• Subnet X now discontiguous• Incoming traffic gets dropped
Workgroup server X.100attached to distribution layerL2 path to client X.1
Client X.1
Routers A & B continue to advertise reachability of subnet X ...
A B
C
X.1 not reachable
X.100 not reachable
275050911_04F9_c3 © 1999, Cisco Systems, Inc.
Rule 4c) Connect Workgroup ServerRule 4c) Connect Workgroup Server• Introduce L2/STP redundancy • Adds a loop (band-aid fix)
Workgroup server X.100attached to distribution layerL2 path to client X.1
Client X.1•VLAN trunk AB forms L2 loop •recovery path for STP•prevents black hole
A B
C
285050911_04F9_c3 © 1999, Cisco Systems, Inc.
Rule 4d) Connect Workgroup ServerRule 4d) Connect Workgroup Server
Real Lessons:☛ Enterprise Server Farms are better☛ L3 demarcation is better☛ Example of why extended L2 is difficult
295050911_04F9_c3 © 1999, Cisco Systems, Inc.
Rule 5a) Use HSRP TrackRule 5a) Use HSRP Track• Review - Hot Standby Router Protocol• Fast recovery can be tuned to 3s or less
X is M.100HSRP PrimaryPriority 200
Y ( becomes M.100)HSRP BackupPriority 100
Z
Router X acts as gateway router for subnet M, IP address M.100. If link Z fails router Ywill take over as M.100 gatewaywith same MAC address
10/100 BaseT
GE or GEC
Subnet Mhosts M.1 M.2 M.3
305050911_04F9_c3 © 1999, Cisco Systems, Inc.
Rule 5b) Use HSRP TrackRule 5b) Use HSRP Track• Track extends HSRP to monitor links to backbone• Ensures shortest path - best outbound gateway
Track interface A - lower priority 75Track interface B - lower priority 75HSRP triggers if both A and B lost
10/100 BaseT
GE or GEC
X is M.100HSRP PrimaryPriority 200
Y ( becomes M.100)HSRP BackupPriority 100
Z
Subnet Mhosts M.1 M.2 M.3
A B
315050911_04F9_c3 © 1999, Cisco Systems, Inc.
Rule 6a) Use Passive InterfacesRule 6a) Use Passive Interfaces
• L3 switches X & Y in distribution layer• 4 VLANs per wiring closet• 10 wiring closets
X Y
ABCD EFGH IJKL MNOP
… Ten totalWiringclosetswitch
Distributionswitch
325050911_04F9_c3 © 1999, Cisco Systems, Inc.
Rule 6b) Use Passive InterfacesRule 6b) Use Passive Interfaces
• What X and Y see is 4*10=40 routed links• Increased protocol overhead & CPU
X Y
A
CB
DEFGEtc.
A.1
C.1B.1
D.1E.1F.1G.1Etc.
A.2
C.2B.2
D.2E.2F.2G.2Etc.
335050911_04F9_c3 © 1999, Cisco Systems, Inc.
Rule 6c) Use Passive InterfacesRule 6c) Use Passive Interfaces
☛ Turns off routing updates & overhead☛ Leave two routed links for redundant paths☛ CDP, VTP, HSRP etc. still function on all links
X Y
A
CB
DEFGEtc.
A.1
C.1 (passive)B.1 (passive)
D.1 (passive)E.1F.1 (passive)G.1 (passive)Etc.
A.2
C.2 (passive)B.2 (passive)
D.2 (passive)E.2F.2 (passive)G.2 (passive)Etc.
345050911_04F9_c3 © 1999, Cisco Systems, Inc.
Rule 7a) Issues With Single Path Rule 7a) Issues With Single Path DesignsDesigns
✔ L3 engine MSFC on core-X reloads
✔ Lights are on but nobody home - HSRP does not recover
✔ Remove passive interface to wiring closet subnets A, B
✔ Provide longer routed recovery path
Single pathto core
GE
Subnet A Subnet B
X
HSRPprimary
Core L3
Access L2
Y
New, longer outbound routes
Outbound case ...
355050911_04F9_c3 © 1999, Cisco Systems, Inc.
Rule 7b) Issues with SingleRule 7b) Issues with Single--Path Path DesignDesign
✔ Recovery must take place in both directions
✔ Routing protocol recovers longer route from X to subnets A, B
✔ Therefore dual-path L3 is better & faster than single-path
Single pathto core
GE
Subnet A Subnet B
X
HSRPprimary
Core L3
Access L2
Y
New, longer routes to A, B
Inbound case ...
365050911_04F9_c3 © 1999, Cisco Systems, Inc.
Rule 8a) Rule 8a) Oversubscription Oversubscription GuidelinesGuidelines
✔ Oversubscription part of all networks - not bad
✔ Non-blocking switches do not mean a non-blocking network
✔ You determine the amount of “blocking”
GE
GE
Non-blockingdesign
GE
GE
Blocking design 2:1
GE
375050911_04F9_c3 © 1999, Cisco Systems, Inc.
Rule 8b) Rule 8b) Oversubscription Oversubscription GuidelinesGuidelines
✔ Oversubscription rules of thumb work well
✔ 20:1 at wiring closet ✔ Less in distribution and
server farm✔ QoS required IFF
congestion occurs✔ Protect real time flows
at congested points
n:1
20:1
Core L3use non-blocking switches
Dual-linkGEC
200 100BaseT
GE8 uplinks
DistributionL3
385050911_04F9_c3 © 1999, Cisco Systems, Inc.
Rule 9) Dual SupervisorsRule 9) Dual SupervisorsHA for Single Attached ServersHA for Single Attached Servers
✔ Single point of failure✔ Dual supervisors - fast stateful recovery✔ No increase in complexity
10/100 BaseT
GE or GEC
Single attached servermission critical application
HA dual supervisorsCatalyst 6XXX
Redundant uplinks
395050911_04F9_c3 © 1999, Cisco Systems, Inc.
Rule 10)Rule 10) Protocol TradeoffsProtocol TradeoffsAutomatic or Manual ConfigurationAutomatic or Manual Configuration
✔ Configuration up front rather than CPU overhead later, for example:
➙ set VTP mode transparent➙ set/clear VLANs for each trunk➙ set trunks on or off➙ set channel on or off
✔ Choose flexibility or determinism
405050911_04F9_c3 © 1999, Cisco Systems, Inc.
Rule 11) Rule 11) UniDirectional UniDirectional Link Link Detection Detection
✔ UDLD detects mismatch when physical layer checks out OK
✔ Prevents various failure conditions including crossed wiring
Tx Fiber
Rx Fiber
The lights are on, BUT …..
415050911_04F9_c3 © 1999, Cisco Systems, Inc.
Building Block Means SurvivableBuilding Block Means SurvivableSelfSelf--contained Backbonecontained Backbone
✔ Autonomous Survivability Unit - HSRP
✔ L3 Broadcast Multicast demarcation
✔ Cookie cutter configuration✔ L3 Demarcation of failure
domain✔ Simple, repeatable,
deterministic✔ Redundancy adds 15% cost
at mission critical points like server farm
L2L3
ASUdelimits failure domain
425050911_04F9_c3 © 1999, Cisco Systems, Inc.
Building Block TemplatesBuilding Block TemplatesUse “As Is” or CombineUse “As Is” or Combine
1) Standard Modelsimple, structured
2) VLAN Modelmore flexible
3) Large Scale Server Farm Model
accommodate dual NIC4) Small Scale Server Farm
Modelaccommodate dual NIC
435050911_04F9_c3 © 1999, Cisco Systems, Inc.
1) Standard Building Block1) Standard Building Blockno loops no loops -- no STP complexityno STP complexity
HSRP PrimarySubnets/VLANs10, 12, 14, 16
HSRP PrimarySubnets/VLANs11, 13, 15, 17
Access L2root switchVLAN 10/11
Subnet 10Subnet 11
GE/GECVLAN Trunks
10/100 BaseT
GE or GEC Dual Path with Tracking
Subnet 12Subnet 13
Subnet 14Subnet 15
Subnet 16Subnet 17
Highly DeterministicL1 maps L2 maps L3No blocking linksShortest path alwaysNot “flexible”
445050911_04F9_c3 © 1999, Cisco Systems, Inc.
2) VLAN Building Block2) VLAN Building Blockmake L2 design match L3 designmake L2 design match L3 design
All All VLANs VLANs terminate at L3 boundaryterminate at L3 boundary
STP rootVLANs 10 12 14 16
HSRP primarysubnets 10 12 14 16
STP rootVLANs 11 13 15 17
HSRP primarysubnets 11 13 15 17
L2L3
All VLANsAll Subnets
GE/GECVLAN Trunks
Dual Path with Tracking
All VLANsAll Subnets
All VLANsAll Subnets
All VLANsAll Subnets
L2 Path
10/100 BaseT
GE or GEC
More flexibleFO forwarding oddBE blocking even etc.
FEBO
FOBE
FEBO
FOBE
FEBO
FOBE
FEBO
FOBE
L2L3
Uplink-Fast
455050911_04F9_c3 © 1999, Cisco Systems, Inc.
3) Large3) Large--Scale Server Farm Scale Server Farm Building BlockBuilding Block
Dual-NIC ServerExample Fault Tolerant Mode (FTM)Same IP Address - seamless recovery
GE/GECVLAN Trunks
Dual Path with Tracking
L2 Path
Access L2UplinkFast
10/100 BaseT
GE or GEC
based on VLAN building blockaggregates traffic - high BW
L2L3
L2L3
STP rootVLANs EVEN
HSRP primarysubnets EVEN
STP rootVLANs ODD
HSRP primarysubnets ODD
465050911_04F9_c3 © 1999, Cisco Systems, Inc.
4) Small4) Small--Scale Server Farm Scale Server Farm Building BlockBuilding Block
Dual-NIC ServerExample Fault Tolerant Mode (FTM)Same IP Address - seamless recovery
Dual Path with Tracking
L2 Path
10/100 BaseT
GE or GEC
Simplified building block with no STP loops
Use if port density permits
Use if no oversubscription (non-blocking) is a requirement
L2L3
L2L3 HSRP primary
subnets EVENHSRP primarysubnets ODD
475050911_04F9_c3 © 1999, Cisco Systems, Inc.
Redundant Backbone ModelsRedundant Backbone Modelsall good all good -- increasing scaleincreasing scale
1) Collapsed L3 Backbone2) Full Mesh3) Partial Mesh4) Dual-Path L2 Switched5) Dual-Path L3 Switched
485050911_04F9_c3 © 1999, Cisco Systems, Inc.
Core L3
Access L2
1) Collapsed L3 Backbonelarge building or small campus
Clients
Collapsed Backbone
GE/GECScale depends on physical plant and policy more than performance
Server Farm10/100 BaseT
GE or GEC
495050911_04F9_c3 © 1999, Cisco Systems, Inc.
Client Blocks
Distribution L3
Access L2
2) Full Mesh Backbonesmall campus - n squared limitation
ServerBlock
Distribution L3
Access L2
Note importance of passive wiringcloset interfaces in meshed designs!
2 blocks - 6 peerings3 blocks - 15 peerings4 blocks - 28 peerings5 blocks - 45 peerings
E or FE PortGE or GEC
505050911_04F9_c3 © 1999, Cisco Systems, Inc.
Distribution/Core L3
Access L2
Client Blocks
Distribution L3
Access L2
3) Partial Mesh Backbone3) Partial Mesh Backbonemedium campus medium campus -- traffic flow to server farmtraffic flow to server farm
ServerBlock
E or FE PortGE or GEC
Predominant traffic pattern
515050911_04F9_c3 © 1999, Cisco Systems, Inc.
4) Dual4) Dual--Path L2 Switched BackbonePath L2 Switched Backboneno STP loops or VLAN trunks in coreno STP loops or VLAN trunks in core
South
ClientBlocks
Dual L2 Backbone
Distribution L3
Core L2
Access L2
“red” coresubnet=VLAN=ELAN
“blue” coresubnet=VLAN=ELAN
WestNorth
E or FE PortGE or GEC
525050911_04F9_c3 © 1999, Cisco Systems, Inc.
5a) Benefits of a L3 Backbone5a) Benefits of a L3 Backbone
✔ Multicast PIM routing control✔ Load balancing✔ No blocked links✔ Fast convergence EIGRP/OSPF✔ Greater scalability overall✔ Router peering reduced✔ IOS features in the backbone
535050911_04F9_c3 © 1999, Cisco Systems, Inc.
Distribution L3
Access L2
5b) Dual-Path L3 Backbonelargest scale, intelligent multicast
Core L3
ServerFarmBlock
Distribution L3
Access L2
All routed links,consider subnetcount !
ClientBlock
E or FE PortGE or GEC
545050911_04F9_c3 © 1999, Cisco Systems, Inc.
Restore ConsiderationsRestore Considerations
✔ Restoring can take longer in some cases - more complex -schedule
✔ On power up L1 may come up before L3 builds routing table -temporary black hole for HSRP
✔ Use “preempt delay” for HSRP
✔ Restoring can take longer in some cases - more complex -schedule
✔ On power up L1 may come up before L3 builds routing table -temporary black hole for HSRP
✔ Use “preempt delay” for HSRP
555050911_04F9_c3 © 1999, Cisco Systems, Inc.
Campus Failover Layer 2 Campus Failover Layer 2 Recovery & TuningRecovery & Tuning
STPTune ‘diameter’ on root switchImproves recovery time maxage
PortFastServer or desktop ports only 1 sMove directly from linkup into forwarding
UplinkFastNo tuning, 2 seconds, wiring closet onlyOnly applies with forwarding & blocking link
BackbonefastConverges 2 sec + 2xFwd_delay for indirect link failuresEliminates maxagetimeout
565050911_04F9_c3 © 1999, Cisco Systems, Inc.
Campus Failover Layer 3 Campus Failover Layer 3 Recovery & TuningRecovery & Tuning
Caution with aggressive tuning
Good when network is stable, highly summarized
HSRP (fast LAN links)Tune hello timer 1 sec, dead timer 3 sec<4s to converge
OSPF (fast LAN links)Tune hello timer 1 sec, dead timer 3 sec<4s to recognize problem, then converge
EIGRP (fast LAN links)Tune hello timer 1 sec, hold timer 3 sec<4s to recognize problem, then converge
575050911_04F9_c3 © 1999, Cisco Systems, Inc.
Keeping Networks Available!Keeping Networks Available!
✔ KISS - eliminate complex L2 ✔ ASU - building blocks✔ Redundant backbone ✔ Redundant L3 paths✔ L3 segments failure domain