book

IP Routing

by Ravi Malhotra

January 2002

Beginner

238 pages

6h 20m

English

O'Reilly Media, Inc.

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What Is IP Routing?

Getting RIP Running
RIP UpdateRIP MetricProcessing RIP UpdatesSteady StateParallel PathsProcess SwitchingFast Switching
Speeding Up ConvergenceSplit horizonCounting to infinityTriggered updatesPoison reverseSetting timers
Routes to hosts
Getting IGRP Running
IGRP Autonomous System NumberIGRP MetricInterface bandwidth, delay, reliability, load, and MTUModifying interface bandwidth, delay, and MTUIGRP routing updatePath bandwidth, delay, reliability, load, and MTUIGRP composite metricModifying IGRP metricsProcessing IGRP updatesParallel PathsUnequal metric (cost) load balancingSteady State
Setting TimersDisabling IGRP Hold-Downs
Multiple Default Routes
Getting EIGRP Running
Neighbor RelationshipReliable Transport ProtocolDiffusing Update Algorithm (DUAL)Reported distanceFeasible distance and successorFeasibility condition and feasible successorLoop freedomTopology tableConvergence in DUAL -- local computationConvergence in DUAL -- diffusing computationProtocol-Dependent ModuleEIGRP Packet FormatInternal routesExternal routes
Automatic SummarizationManual Summarization
Verifying Neighbor RelationshipsStuck-in-ActiveIncrease active timerEIGRP Bandwidth on Low-Speed LinksNetwork LogsIOS Version Check, Bug ListsDebug Commands
Getting RIP-2 Running
RIP-1/RIP-2 Interworking
VLSMUse of Subnet ZeroClassless Inter-Domain Routing (CIDR)
Getting OSPF Running
Backbone AreaBackbone RouterArea or Regular AreaInternal RouterArea Border Router (ABR)Autonomous System Boundary Router (ASBR)Stub AreaTotally Stubby AreaNot So Stubby Area (NSSA)OSPF Topological DatabaseOSPF Route Types
Neighbor Discovery: The Hello ProtocolRouter IDArea IDChecksumAuthenticationNetwork maskHello-intervalOptionsRouter priorityRouter dead-intervalDesignated router (DR)Backup designated routerNeighbor router ID listDR/BDR ElectionInterface StateNeighbor RelationshipDatabase ExchangeRouter LSA (type 1)Network LSA (type 2)Summary LSA (type 3)ASBR summary LSA (type 4)External LSA (type 5)NSSA external LSA (type 7)Flooding of LSAs
Summarizing at the ABR (Inter-Area Summarization)Summarizing at the ASBR (or External Route Summarization)
Stub AreasTotally Stubby AreasNSSAs
OSPF HierarchyIP AddressingRouter IDDR/BDRBackbone AreaNumber of Routers in an AreaNumber of NeighborsRoute SummarizationVLSMStub AreasVirtual LinksOSPF Timers
OSPF Area IDsOSPF Does Not StartVerifying Neighbor RelationshipsRoute SummarizationOverloaded RoutersSPF OverrunUsing the LS DatabaseNetwork LogsDebug Commands
BackgroundAS TypesGluing AS to AS... Physical Connectivity in the InternetInternet Registries: IP Addresses and AS NumbersClassless Inter-Domain Routing (CIDR)Acquiring an IP AddressAcquiring an AS Number
Starting BGPNeighbor RelationshipBGP Message TypesOpenUpdateNotificationKeepaliveOriginating RoutesE-BGP Versus I-BGPSynchronizationThe BGP TableAttributesORIGIN (type code 1)AS-PATH (type code 2)NEXT-HOP (type code 3)MED (type code 4)WeightLOCAL-PREF (type code 5)Atomic Aggregate (type code 6)Aggregator (type code 7)CommunityPath Selection
Filtering by Prefix (Address/Mask) InformationFiltering by AS-PATH Information
Design AlternativesA Case Study
ServicesNetwork ArchitectureAddressing/RoutingOperationsPrice
Filter Routing InformationBlock All Updates on an InterfaceFilter the Routes Sent out in UpdatesFilter the Routes Received in UpdatesApply an Offset to a Routing Metric
How to RedistributeMany Pitfalls...... and a Couple of Strategies

Content preview from IP Routing

Troubleshooting BGP

You might encounter your first problem with BGP when configuring a new peering relationship. The BGP session between the peers may not enter the Established state (the output of show ip bgp neighbor may show other states, such as Idle, Connect, or Active). Here are the first steps you should take when troubleshooting BGP:

Check the infrastructure between the peers: an ICMP ping test between the peers is a quick test of layer-3 reachability between the peers.
If layer 3 reachability exists between the peers, the configuration of the peers may be in error. Check the BGP configuration of neighbor IP addresses and AS numbers on each peer.
Check for IP filters (access lists) or firewalls between the peers that would prevent a BGP TCP session (on port 179) from being formed.
Is there a BGP version mismatch between the peers? Look for the BGP neighbor ip-address version number sub-command.

Once the neighbors have entered into the Established state, you may find that no prefixes or only some prefixes are being exchanged. Here are the steps you should take:

If no prefixes are being exchanged, you may want to go back and make sure that the peers are indeed in an Established state.
If some but not all prefixes are being exchanged, check to see if a filter (an access list, a prefix filter, or an attribute filter such as an AS-PATH filter) is blocking the update. The show ip bgp neighbor ip-address command will show the filters that are applied to the BGP session.
Filter changes ...