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1、Ericsson AXI 520/580 Internet EngineerModule 10: IS-ISModule ObjectivesAfter successfully completing this module, you will be able to: Describe IS-IS operationExplain the reason for a Designated Intermediate SystemDescribe IS-IS areas and levelsConfigure IS-ISMonitor and troubleshoot IS-IS using the

2、 CLIDisplay and interpret the Link State Database (LSD)IS-ISWhere we are goingWhat is IS-IS?Integrated IS-ISIS-IS ConceptsIS-IS and OSPF ComparisonIS-IS Protocol Data UnitsNeighbors and AdjacenciesDesignated Intermediate System (DIS)IS-IS MetricsConfiguring IS-IS Monitoring and Troubleshooting IS-IS

3、What Is IS-IS?An interior gateway protocol (IGP) based on the shortest path first (SPF) algorithmUses link-state information to make routing decisionsDeveloped for routing International Organization for Standardization (ISO) Connectionless Network Protocol (CLNP) packetsIP was added laterDefined in

4、ISO/IEC 10589, RFC 1195 and RFC 2763Integrated IS-ISImplementation of IS-IS for routing IP in addition to CLNPAlso called Dual IS-IS All routers run a single routing algorithmIS-IS routers exchange Link-State PDUs (LSPs)Similar to OSPF LSAs/Link State Update PacketsIS-IS PDUs are the L2 protocol use

5、d to transmit the info NOT IPIP reachability information is included in the updatesJUNOS software does not support CLNP/CLNS routing!IS-IS ConceptsA single autonomous system (AS) End Systems: network entities that send and receive packets (Hosts)Intermediate Systems: send and receive packets and rel

6、ay (forward) packets (Routers)IS-IS packets are called Protocol Data Units (PDUs)A single AS can be divided into smaller groups called areasOrganized hierarchicallyLevel 1 intermediate systems route within an area or toward a Level 2 systemAttached bitLevel 2 intermediate systems route between areas

7、 and toward other ASsIS-IS AreasL1/L2L1/L2L1/L2L1L2L1L1L1L1L1L2In IS-IS, links separate areasOSPF AreasABRABRABRIn OSPF, routers separate areasIS-IS and OSPFBoth IS-IS and OSPF:Maintain Link State Databases and construct a Shortest Path Tree Dijkstra algorithmUse Hello packets to form and maintain a

8、djacenciesUse a two-level hierarchyProvide for address summarization between areasElect a designated routerHave authentication capabilitiesNetwork Entity TitlesIS-IS uses the CLNP protocolEven in an IP-only environment, all routers must have an ISO addressISO address is a network address or Network

9、Entity Title (NET) 49.0001.00a0.c96b.c490.0049.0001.1921.6816.9018.00First Byte of Area ID is the authority and format indicator (AFI) Area IDSystem IDSEL1-13 BytesLevel 2 Routing6 BytesLevel 1 Routing1IS-IS Protocol Data Units (PDUs)Where we are goingHello PDUsLink State PDUsSequence Number PDUsCom

10、pletePartialThe Building Blocks for PDUsType Length Values (TLVs)IS-IS Hello PDUsHello protocol used to build and maintain adjacenciesSimilar to the Hello protocol in OSPFSeparate Hellos for:Broadcast networksPoint-to-Point networksHellos are transmitted at regular intervalsHello PDUs:Identify the d

11、eviceDescribe its capabilitiesDescribe the parameters of the interfaceIS-IS Link State PDUsLink State PDUs (LSPs) are used to build the Link State databaseSimilar to the Link State Advertisements in OSPFSeparate LSPs for:Level 1 SystemsLevel 2 SystemsLSPs are sent as a result of a network change, du

12、ring adjacency formation, and in response to a Sequence Number PDU (described next)Link State PDUs:Identifies an ISs adjacenciesDescribe the state of its adjacenciesDescribes its reachable address prefixes (routes)IS-IS Sequence Number PDUsPartial Sequence Number PDUs (PSNPs)Used to:Maintain the Lin

13、k State database synchronizationAcknowledge LSPs from a neighbor on a point-to-point networkRequest a copy of a missing LSP on a broadcast networkSeparate type for Level 1 and 2 SystemsContains specific header information for a particular LSP being acknowledged or requestedComplete Sequence Number P

14、DUs (CSNPs)Used to:Maintain the Link State database synchronizationSent periodically by all ISs on point-to-point networksOnly sent by DIS on broadcast networksSeparate type for Level 1 and 2 SystemsContains header information for all LSPs in ISs Link State DatabaseType-Length-Values (TLVs)Each piec

15、e of IS-IS information is defined as an object with 3 attributes:Object Type: a predefined code for the type of information contained in the objectObject Length: the length of the informationAllows for variable-length objectsObject Value: the actual information defined by the Type attributeTLVs are

16、the building blocks of IS-IS PDUs which are used for information exchangeSome TLVs are used in multiple PDUsSome TLVs are PDU-specificSimilar to OSPF packet- and LSA-specific fieldsSome Common TLVsIP Interface AddressRFC 1195132Area AddressesISO 105891Dynamic Hostname MappingRFC 2763137IP External I

17、nformationRFC 1195130Protocols SupportedRFC 1195129IP Prefix, Mask, and MetricsRFC 1195128AuthenticationISO 1058910LSP EntriesISO 105899PaddingISO 105898Neighbor LAN IDISO 105896IS Neighbor MetricsISO 105892Used forDefined inTLV CodeNeighbors and AdjacenciesL1 routers will never form an adjacency wi

18、th an L2 routerThe reverse is also trueFor L1 adjacencies, Net-IDs must be sameFor L2 adjacencies, Net-IDs may be differentL1/L2L1L1L1L2L2Level 1 HelloLevel 2 HelloDesignated Intermediate SystemIS-IS elects a Designated Intermediate System (DIS) on broadcast multi-access networks, based on priorityS

19、eparate DIS is elected for L1 and L2 (could be the same router)The IS-IS network is considered a routerCalled a pseudo-nodeEach router advertises a single link to the pseudo-nodeIncluding the DISEach router forms an adjacency with each of its neighbors on a broadcast multi-access networkDIS acts as

20、representative of the pseudo-nodeDIS advertises the pseudo-node to all attached routersNo Backup DIS in IS-ISTroubleshooting IS-IS AdjacenciesIS-IS adjacencies do not require or rely on IP configurationUnlike OSPFNo adjacencyPhysical/Link layer connectivityMismatchedAreas (If L1 router)LevelFailure

21、to support minimum MTU of 1492Lack of, or malformed ISO-NETNo NET configuredFailure to include lo0 as an IS-IS interfaceIS-IS MetricsAny single link can have a maximum value of 63Arbitrary and assigned by network administratorPath links are calculated by summing link valuesA single required default

22、metric with a maximum path value of 1024, interpreted as costJUNOS IS-IS SupportIS-IS support with: Multiple areasMultiple levelsAuthenticationSummarizationRoute leakingTraffic Engineering TLVsWide metricsMesh groupsOverloadHello interval, LSP lifetime, etc.Configuring IS-IS 1edituserhost# set proto

23、cols isis interface ge-0/0/0.0 level 1 disable edituserhost# set protocols isis interface at-0/1/1.100 level 2 disable edituserhost# show protocols isis isis interface ge-0/0/0.0 level 1 disable; interface at-0/1/1.100 level 2 disable; Configuring IS-IS 2Must include family iso on all interfaces you

24、 want to run IS-IS on and a NET on one of the routers interfaces (usually lo0) edituserhost# show interfaces ge-0/1/0 unit 0 family iso; lo0 unit 0 family inet address 192.168.2.1/32; family iso address 49.0001.0192.0168.0201.00; Monitoring IS-IS OperationWhere we are goingVarious show” commands exi

25、st to provide detailed information on the operation of IS-ISShow isis:InterfaceAdjacencySPF logStatisticsRouteDatabaseIS-IS tracingshow isis interfaceUse show isis interface to display the IS-IS parameters associated with an interfaceuserhost show isis interface ?Possible completions: Execute this c

26、ommand Interface name brief Show brief status detail Show detailed status userhost show isis interface IS-IS interface database:Interface L CirID Level 1 DR Level 2 DR L1/L2 Metriclo0.0 0 0 x1 Disabled Passive 0/0so-0/1/0.0 2 0 x1 Disabled Point to Point 10/10so-0/1/1.0 2 0 x1 Disabled Point to Poin

27、t 10/10so-0/1/2.0 2 0 x1 Disabled Point to Point 10/10show isis adjacencyUse show isis adjacency to display IS-IS parameters adjacency statususerhost show isis adjacency ?Possible completions: Execute this command brief Show brief status detail Show detailed status system-id Display entries for spec

28、ified system userhost show isis adjacency IS-IS adjacency database:Interface System L State Hold (secs) SNPAso-0/1/2.0 Denver 2 Up 24so-0/1/3.0 SanFran 2 Up 28so-0/2/2.0 Toronto 2 Up 23so-0/2/3.0 Amsterdam 2 Up 26show isis adjacency detailDisplay detailed IS-IS adjacency information with the detail

29、switchuserhost show isis adjacency detail IS-IS adjacency database:Denver Interface: so-0/1/2.0, Level: 2, State: Up, Expires in 25 secs Priority: 0, Up/Down transitions: 1, Last transition: 00:15:27 ago Circuit type: 2, Speaks: IP IP addresses: 10.0.18.2clear isis adjacencyClear IS-IS adjacencies w

30、ith the clear isis adjacency command userhost show isis adjacency IS-IS adjacency database:Interface System L State Hold (secs) SNPAso-0/1/2.0 Denver 2 Up 24so-0/1/3.0 SanFran 2 Up 28so-0/2/2.0 Toronto 2 Up 23so-0/2/3.0 Amsterdam 2 Up 26userhost clear isis adjacency Toronto userhost show isis adjace

31、ncy IS-IS adjacency database:Interface System L State Hold (secs) SNPAso-0/1/2.0 Denver 2 Up 22so-0/1/3.0 SanFran 2 Up 26so-0/2/3.0 Amsterdam 2 Up 24show spf logDisplay information about SPF operation with the show spf log commanduserhost show isis spf log IS-IS level 1 SPF log:Start time Elapsed (s

32、ecs) Count ReasonTue Apr 17 16:13:26 0.000039 1 ReconfigTue Apr 17 16:13:32 0.000062 1 Updated LSP host.00-00Tue Apr 17 16:28:26 0.000064 1 Periodic SPFIS-IS level 2 SPF log:Start time Elapsed (secs) Count ReasonTue Apr 17 16:13:26 0.000025 1 ReconfigTue Apr 17 16:13:32 0.000051 1 Updated LSP host.0

33、0-00Tue Apr 17 16:13:57 0.000087 2 New adjacency Denver on so-0/1/2.0Tue Apr 17 16:14:03 0.000241 6 Updated LSP Atlanta.00-00Tue Apr 17 16:26:38 0.000298 1 Periodic SPFshow isis statisticsDisplay various IS-IS statistics information with the show isis statistics commanduserhost show isis statistics

34、IS-IS statistics for host:PDU type Received Processed Drops Sent RexmitLSP 17 17 0 2 0IIH CSNP 99 99 0 294 0PSNP 3 3 0 12 0Unknown 0 0 0 0 0Totals 309 309 0 879 0Total packets received: 309 Sent: 879SNP queue length: 0 Drops: 0LSP queue length: 0 Drops: 0SPF runs: 17Fragments rebuilt: 5LSP regenerat

35、ions: 2Purges initiated: 0Displaying IS-IS Routesuserhost show isis route IS-IS routing table Current version: L1: 3 L2: 5Prefix L Version Metric Type Interface Via10.0.0.0/24 2 5 20 int so-0/1/2.0 Denver 10.0.1.0/24 2 5 20 int so-0/1/2.0 Denver 10.0.2.0/24 2 5 30 int so-0/1/2.0 Denver 10.0.8.0/24 2

36、 5 30 int so-0/1/2.0 Denver . . . userhost show route protocol isis inet.0: 31 destinations, 31 routes (31 active, 0 holddown, 0 hidden)+ = Active Route, - = Last Active, * = Both10.0.0.0/24 IS-IS/18 00:27:18, metric 20, tag 2 to 10.0.18.2 via so-0/1/2.010.0.1.0/24 IS-IS/18 00:27:18, metric 20, tag

37、2 to 10.0.18.2 via so-0/1/2.010.0.2.0/24 *IS-IS/18 00:27:18, metric 30, tag 2show isis databaseDisplay IS-IS database entries with the show isis database commanduserhost show isis database IS-IS level 1 link-state database:LSP ID Sequence Checksum Lifetime Attributeshost.00-00 0 x3 0 x48ba 1132 L1 L

38、2 1 LSPsIS-IS level 2 link-state database:LSP ID Sequence Checksum Lifetime AttributesDenver.00-00 0 x6 0 xb978 1154 L1 L2host.00-00 0 x4 0 x140c 1154 L1 L2wash-dc.00-00 0 x1d7 0 x7f37 683 L1 L2Atlanta.00-00 0 x1d3 0 xe603 1024 L1 L2Houston.00-00 0 x1c8 0 x8b1c 677 L1 L2Dallas.00-00 0 x1ca 0 x1571 1

39、103 L1 L2NewYork.00-00 0 x1dd 0 x178a 779 L1 L2 7 LSPsshow isis database extensiveuserhost show isis database extensive IS-IS level 2 link-state database:Denver.00-00 Sequence: 0 x6, Checksum: 0 xb978, Lifetime: 1030 secs IS neighbor: host.00 Metric: 10 IP prefix: 192.168.0.1/32 Metric: 0 Internal I

40、P prefix: 10.0.18.0/24 Metric: 10 Internal IP prefix: 10.0.16.0/24 Metric: 10 InternalTLVs: Area address: 49.0001 (3) Speaks: IP IP router id: 192.168.0.1 IP address: 192.168.0.1 Hostname: Denver IP prefix: 10.0.16.0/24, Internal, Metric: default 10 IP prefix: 10.0.18.0/24, Internal, Metric: default 10 IP prefix: 192.168.0.1/32, Internal, Met