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Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 1 Integrated IS-IS Wayne Lewis / Torrey Suzuki Session Number Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 2 Agenda • ISIS Overview • CLNS Addressing • ISIS Areas • ISIS PDUs • LSP Header • Flooding • Configuration Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 3 Teminology • AFI Authority and Format Identifier (the first octet of all OSI NSAP addresses - identifies format of the rest of the address) • CLNP Connection-Less Network Protocol (ISO 8473 - the OSI connectionless network layer protocol - very similar to IP) • ES End System (The OSI term for a host ) • IS Intermediate System (The OSI term for a Router) • ES-IS End System to Intermediate System Routing exchange protocol (ISO 9542 - OSI protocol between routers and end systems). • IS-IS Intermediate System to Intermediate System Routing Exchange Protocol (the ISO protocol for routing within a single routing domain. • IS-IS Hello A Hello packet defined by the IS-IS Protocol • LSP Link State Packet (a type of packet used by the IS-IS protocol). Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 4 IS-IS Overview • IS-IS was originally designed for use as a dynamic routing protocol for the ISO Connectionless Network Protocol (CLNP). (ISO10589 or RFC 1142) • Adapted for routing IP in addition to CLNP (RFC1195) as Integrated or Dual IS-IS • IS-IS is a Link State Protocol similar to the Open Shortest Path First (OSPF) Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 5 IS-IS Overview • IS-IS is an Interior Gateway Protocol (IGP) used for routing within an Autonomous System (AS), also referred to as a routing domain. • BGP is normally used for dynamic routing between IP domains • ISO-IGRP is a Cisco proprietary routing protocol that can be used between CLNP domains Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 6 IS-IS Overview • 3 network protocols work together to deliver the ISO-defined Connectionless Network Service CLNP IS-IS ES- IS - End System to Intermediate System Protocol • All 3 protocols independently ride over layer 2. Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 7 IS-IS Overview • CLNP is the ISO equivalent of IP for datagram delivery services (ISO 8473, RFC 994) • IS-IS carries routing information. Integrated IS-IS works within the ISO CLNS framework even if used for routing IP (ISO 8473, RFC 1142) • ES-IS is a dynamic protocol hosts used to discover routers. Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 8 IS-IS Overview • End System Hellos (ESH) from Hosts and Intermediate System Hellos (ISH) for Routers are used for ES-IS neighbor discovery • Intermediate System to Intermediate Systems Hellos (IIH) are used for establishing IS-IS layer3 adjacencies Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 9 CLNS Addressing Area System ID N-SEL CLNS Addressing consists of 3 parts Area – Variable System ID N-SEL(ector) Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 10 NSAPs and Addressing • ISO/IEC 10589 distinguishes only 3 fields in the NSAP address format DSP IDP AFI IDI High Order DSP Variable Length Area Address System ID 6 Bytes NSEL 1 Byte • Area Address: variable length field composed of high order octets of the NSAP excluding the SystemID and SEL fields • SystemID: defines an ES or IS in an area. Cisco implements a fixed length of 6 octets for the SystemID • NSEL: selector, also designated as N-selector. It is the last byte of the NSAP and identifies a network service user (transport entity or the IS network entity itself) Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 11 NSAPs and Addressing • NSAP: Network Service Access Point • An NSAP has an address that consists of 3 parts. Variable length area-address 6 Byte system ID Byte n-selector (indicating transport layer) Total length between 8 and 20 bytes Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 12 NETs Versus NSAPs • NET: Network Entity Title • Is the address of the network entity itself • A NET is an NSAP where n-selector is 0 • A NET implies the routing layer of the IS itself (no transport layer) • ISs (routers) do not have any transport layer (selector=0) • Multiple NETs are like secondary IP addresses - only use them when merging or splitting areas Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 13 CLNS Addressing: AFI Values Address Domain X.121 ISO DCC ISO 6523 Local AFI Value 37 39 47 49 • X.121 - Int’l plan for public data networks • ISO DCC - Data country code • IS0 6523 ICD - Telex • Local - For local use within network domain only Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 14 CLNS Addressing: Requirements and Caveats • All routers in an area must use the same area address. • An end system may be adjacent to a level 1 router only if they both share a common area address. • Each node in an area must have a unique System ID. • All level 2 routers in a domain must have unique System IDs in relation to each other. • All systems belonging to a given domain must have System IDs of the same length in their NSAP addresses. • The maximum size of an NSAP is 20 bytes. Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 15 CLNS Addressing: Requirements and Caveats • Minimum of 8 bytes allowed on Cisco routers. 1 byte for area, 6 bytes for system ID and 1 byte for N-selector. AFI prefix recommended to make minimum of 9 bytes • At least one NSAP is required per node. • All NSAPs on the same router must have the same system ID. Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 16 CLNS Addressing: NSAP Examples Example 1 47.0001.aaaa.bbbb.cccc.00 Area = 47.0001, SysID = aaaa.bbbb.cccc, NSel = 00 Example 2 39.0f01.0002.0000.0c00.1111.00 Area = 39.0f01.0002, SysID = 0000.0c00.1111, NSel = 00 Example 3 49.0002.0000.0000.0007.00 Area = 49.0002, SysID = 0000.0000.0007, Nsel = 00 Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 17 CLNS Addressing: NSAP Examples 39.0f01.0003.6666.6666.6666.00 39.0f01.0002.4444.4444.4444.00 39.0f01.0002.3333.3333.3333.00 39.0f01.0004.7777.7777.7777.00 39.0f01.0001.2222.2222.2222.00 39.0f01.0004.8888.8888.8888.00 39.0f01.0001.1111.1111.1111.00 Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 18 CLNS Addressing: How do most ISPs define System IDs? The LOOPBACK IP address: 192.168.3.25 The AREA the router under is: 49.0001 IP Address conversion process to system ID: 192.168.3.25 192.168.003.025 1921.6800.3025 49.0001.1921.6800.3025 Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 19 Areas and backbone routers • ISIS has a 2 layer hierarchy The backbone (level-2) The areas (level-1) • An IS can be Level-1 router (intra-area routing) Level-2 router (inter-area routing) Level-1-2 router (intra and inter-area routing) • For each level (1 and 2) a DIS will be elected on LANs Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 20 Areas and backbone routers • Level-1 router Has neighbors only on the same area Has the level-1 LSDB with all routing information for the area Use the closest Level-2 router to exit the area This may result in sub-optimal routing • Level-2 router May have neighbors in other areas Has a Level-2 LSDB with all information about inter-area routing Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 21 Areas and backbone routers • Level-1-2 router May have neighbors on any area. Has two LSDBs: Level-1 for the intra-area routing Level-2 for the inter-area routing If the router has adjacencies to other areas, it will inform the level-1 routers (intra-area) it is a potential exit point for the area Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 22 Areas and backbone routers Area 49.001 L1 L1L2 Area 49.003 Area 49.0002 L1 Presentation_ID L1L2 © 2002, Cisco Systems, Inc. All rights reserved. L1L2 L1 23 Areas and backbone routers • Backbone MUST BE L2 contiguous Area-3 L1-only L1L2 Area-2 L2-only L1L2 L1-only L1L2 Area-4 L1L2 L1-only Area-1 L1L2 L1-only Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 24 Areas and backbone routers area 1 router A “I’m in area 2 and ALL my neighbors are in the same area. I must be a L1-only router ?” area 2 rtr D area 3 rtr F C area 2 rtr B!! NO !! area 2 rtr Rtr C must have a full L2 LSDB to route between areas 1, 3 and 4. Remember, the backbone must be contiguous. area 2 rtr E area 4 rtr G Remember, the backbone must be contiguous. ISIS router cannot determine if they need to be L1 or L1L2 So all routers try to be a L1L2 IS by default. Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 25 Areas and SPF calculation • ISs are identified with NETs, 8 to 20 bytes Variable length area-address 6 Byte system ID (unique in the whole domain for level-2 routers) 1 Byte n-selector (set to 0) • Each IS is in exactly ONE area • Area borders are on links, not on routers. • 2 Separate LSDBs, 2 separate SPF runs Level-1 and Level-2 LSDBs Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 26 SPF (Dijkstra) and Partial Route Calculation • SPF (Dijkstra) is run when topology has to be calculated (SPF tree) • PRC (Partial Route Calculation) is executed when IP routing information has to be calculated • If an IS receives an LSP where only IP information has changed, it will run PRC only (less CPU) Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 27 ISIS PDUs • ISIS packets are encapsulated directly in a data-link frame • There is no CLNS or IP header • Hello PDUs (IIH, ISH, ESH) • LSP – Non-Pseudonode LSP – Pseudonode LSPs • CSNP • PSNP Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 28 ISIS Packet Header # of Octets Protocol Identifier 1 Header Length 1 Version 1 ID Length 1 Packet Type 1 Version 1 Reserved 1 Max. Area Addresses 1 Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 29 Summary of Packet Types Presentation_ID L1 - LAN 15 L2 - LAN Hello Hello Point-to-point Hello 16 L1 LSP 18 L1 CSNP 24 L2 CSNP 25 L1 PSNP 26 L2 PSNP 27 © 2002, Cisco Systems, Inc. All rights reserved. 17 30 Encapsulation ISIS Datalink header (OSI family 0xFEFE) ESIS Datalink header (OSI family 0xFEFE) CLNS Datalink header (OSI family 0xFEFE) Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. ISIS fixed header (first byte is 0x83) ISIS TLVs ESIS fixed header (first byte is 0x81) ESIS TLVs CLNS header (with NSAPs) (first byte is 0x80) User data 31 Mac layer addresses • On LANs IS-IS PDUs are forwarded to the following well known MAC layer broadcast addresses AllL1ISs 01-80-C2-00-00-14 AllL2ISs 01-80-C2-00-00-15 AllIntermediateSystems 09-00-2B-00-00-05 AllEndSystems 09-00-2B-00-00-04 Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 32 Hello PDUs # of Octets Common Fixed Header 8 Circuit type Reserved Source ID # of Octets Common Fixed Header 8 1 Circuit type Reserved Source ID ID Length 1 ID Length Holding Time 2 Holding Time 2 Packet Length 2 Packet Length 2 Local Circuit ID 1 Point-to-Point ISIS Hello r Priority LAN ID 1 ID Length + 1 LAN ISIS Hello Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 33 Hello PDUs • IIHs are between routers (IS-IS) • Exchanged by ISs to form adjacencies Point-to-Point IIH Level-1 LAN IIH Level-2 LAN IIH • Mutipoint & P2P IIHs are padded to full MTU Size Useful to detect MTU inconsistencies Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 34 Hello PDUs • Point-to-Point ISIS Hello • Circuit-type: 1 - Level 1-Only 2 - Level 2-Only ( no IS-ES hello) 3 - Level 1-2 • Source ID: Transmitting Router’s Network Layer Address • Holding time: time at which neighbors can legally declare this route dead if they haven’t gotten a hello from it. • Packet Length: the Length of the entire ISIS hello message • Local Circuit ID: identifier to the interface and unique relative to the transmitting router’s other interfaces Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 35 Hello PDUs • LAN ISIS Hello • Priority: the transmitting routers’ priority for becoming designated router on the LAN, with higher #s having a higher priority • LAN ID: the name of the LAN as assigned by the DIS. It consists of DIS-ID + extra octet to differentiate this LAN from others with the same DIS Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 36 Hello PDUs • ISs form adjacencies by sending/receiving IIH • ISs discover ES by listening to ESHs • ESs discover IS by listening to ISHs • DIS (Designated Intermediate System) will drive the flooding on LANs create a special LSP describing the LAN topology Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 37 Hello PDUs ES sends ESH IS send ISH for ES ISIS adjacency through IIH • ISs send IIH to establish ISIS adjacencies • ISs listen to ESH to discover ESs • ISs send ISH for ESs • ESs sends ESH and listen to ISH • ESs select IS as default router by listening to ISH Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 38 Node and Pseudonode LSP • 2 Kinds of Link State PDUs • Non-Pseudonodes represent routers • Pseudonodes represents LANs (created by the DIS) • A level-1 router will create a level-1 LSP • A level-2 router will create a level-2 LSP • A level-1-2 router will create a level-1 LSP and a level-2 LSP Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 39 Non-Pseudonode LSP generation • Each IS will create and flood a new NonPseudonode LSP When a new neighbor comes up or goes away When new IP prefixes are inserted or removed When the metric of a link did change When refresh interval timer expires Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 40 Pseudonode LSP generation • The DIS will create and flood a new Pseudonode LSP When a new neighbor comes up or goes away When refresh interval timer expires • Pseudonode LSP is created by the DIS One for each level (level-1 and/or level-2) One for each LAN • Reduces adjacencies and flooding over LAN subnets Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 41 Pseudonode LSP generation DIS DIS PSN • Broadcast link represented as virtual node, referred to as Pseudonode (PSN) • PSN role played by the Designated Router (DIS) • DIS election is preemptive, based on interface priority with highest MAC address being tie breaker • IS-IS has only one DIS. DIS helps routers on Broadcast link to synchronize their IS-IS databases Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 42 LSPDB without Pseudonode LSP for routerB IS: 10 A 10 C 10 D ES: 10 E LSP for routerA IS: 10 B 10 C 10 D ES: 10 E LSP for routerD IS: 10 A 10 B 10 C ES: 10 E LSP for routerC IS: 10 A 10 B 10 D ES: 10 E Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. endsystem E 43 Pseudonode in the LSPDB LSP for routerA IS: 10 P LSP for routerA IS: 10 P LSP for the Pseudonode P IS: 0 A 0B 0C 0D ES: 0 E LSP for routerA IS: 10 P LSP for routerA IS: 10 P Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. endsystem E 44 CSNP/PSNP • For both Level 1 & Level 2 Databases, we have CSNPs & PSNPs Level 1 CSNP Level 2 CSNP Level 1 PSNP Level 2 PSNP Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 45 CSNP # of Octets Common Fixed Header 8 Packet Length 2 Source ID ID Length + 1 Start LSP ID ID Length + 2 End LSP ID ID Length + 2 Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 46 Complete Sequence Number PDU • Describes all LSPs in your LSDB (in range) Contains an address range LSPid, seqnr, checksum, remaining lifetime • Used at 2 occasions Periodic multicast by DIS (every 10 seconds) On p2p links when link comes up • Created and flooded by the DIS Every 10 seconds On each LAN the IS is the DIS • If LSDB is large, multiple CSNPs are sent Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 47 Partial Sequence Number PDU • PSNPs have 2 functions Exchanged by ISs on p2p links (ACKs) Acknowledge receipt of an LSP Request transmission of latest LSP • PSNPs describe LSPs by its header LSP identifier Sequence number Remaining lifetime LSP checksum Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 48 LSP header • The LSP header contains LSP-id Sequence number Remaining Lifetime Checksum Type of LSP (level-1, level-2) Attached bit Overload bit Partition bit Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 49 LSP Header • LSP identifier consists of 3 parts Source ID System-ID of router (non-PN) or DIS (Pseudonode) Pseudonode ID Zero for router LSP, non-zero for Pseudonode LSP LSP number 00c0.0040.1234.01-00 System ID Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. Frag-Nr PN-ID 50 LSP Header • LSP sequence number Used to determine the newest LSP version • LSP remaining lifetime Used to purge old LSPs • LSP checksum • LSP type Level-1 or Level2 Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 51 LSP Header • LSP Attached bit Set in the level-1 LSP by a L1-L2 router if it has connectivity to another area Indicate to the area routers (level-1) that it is a potential exit point of the area Level-1 routers select the closest (best metric) level-2 router with the ATT-bit set Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 52 LSP Header • LSP Overload bit Set by the IS when it has an overload problem on its LSDB Indicates that the router has an incomplete LS database, and hence cannot be trusted to compute any correct routes Is used in the LSDB but topology behind it is not calculated Therefore other routers do not compute routes which would require the PDU to pass through the overloaded router. Exception - ES neighbors - since these paths are guaranteed to be non looping Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 53 LSP Header • LSP Partition bit To recover from partitioned areas ISIS uses virtual links Router with partition bit set does support partition repair and may be used as end point of virtual link Area partitioning is not supported Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 54 Reasons for Flooding • All routers generate an LSP • All LSPs need to be duplicated and sent to all routers in the network if LSPDB is not synchronized, routing loops might occur • IS-IS’ two components are the SPF computation and reliable flooding Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 55 Reasons for Flooding • Sending needs to be robust we can not use the routing table or LSPDB to find a path over which to send LSPs. No smart tricks. • Send LSPs over all paths to be sure except the intf on which we received it Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 56 What triggers a new LSP ? • When something changes … adjacency came up or went down interface up/down (connected IP prefix !) redistributed IP routes change inter-area IP routes change an interface is assigned a new metric most other config changes Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 57 What to do with a new LSP ? • Create new LSP, install in your own LSPDB and mark it for flooding • Send the new LSP to all neighbors • Neigbors flood the LSP further • Only flood new LSPs, ack old ones because we have state in our LSPDB , we can prevent infinite looping of LSPs Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 58 Basic flooding rules • When receiving a new LSP, compare with old version of LSP in LSPDB. if newer, install it in the LSPDB, flood to all other neighbors, (except the one you got it from, send that one an ACK). check if you need run SPF. if same age, only send ACK, don’t flood if older, send latest LSP from our LSPDB Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 59 Flooding of LSPs • New LSPs are flooded to all neighbors • It is necessary that all ISs get all LSPs • Each LSP has a sequence number • Reliable on p2p links with ACKs (PSNPs) Partial Sequence Number PDU Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 60 Flooding on a p2p link • Once the adjacency is established both IS send CSNP packet • Missing LSPs are sent by both ISs if not present in the received CSNP • Missing LSPs may be requested through PSNP Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 61 Flooding on a p2p link RTA RTB RTC Interface 1 Interface 4 Interface 2 LSP RTA.00-00 SEQ#100 PSNP RTA.00-00 SEQ#100 Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. Interface 3 LSP RTA.00-00 SEQ#100 PSNP RTA.00-00 SEQ#100 62 Flooding on a LAN(Broadcast Links) • On LANs only, there’s a Designated Router (DIS) • DIS has two tasks Creating and updating the Pseudonode LSP Conducting the flooding over the LAN • A DIS is elected for each LAN • DIS election is based on priority • Breaking-tie is the highest SNPA (MAC address) • DIS election is deterministic Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 63 Flooding on a LAN(Broadcast Links) Interface 2 RTA (DIS) RTB Interface 1 Interface 3 RTC RTB RTA CSNP LSP RTA.00-00 SEQ#100 Presentation_ID RTA © 2002, Cisco Systems, Inc. All rights reserved. LSP RTC.00-00 SEQ#1 PSNP RTB.00-00 SEQ#200 RTB 64 How to Configure ? e0 e0 s0 s0 R1 R1 ! interface Loopback0 ip address 172.16.1.1 255.255.255.255 ! interface Ethernet0 ip address 172.16.12.1 255.255.255.0 ip router isis ! router isis passive-interface Loopback0 net 49.0001.1720.1600.1001.00 ! Presentation_ID R3 R2 © 2002, Cisco Systems, Inc. All rights reserved. R2 ! interface Loopback0 ip address 172.16.2.2 255.255.255.255 ! interface Ethernet0 ip address 172.16.12.2 255.255.255.0 ip router isis ! interface Serial0 ip address 172.16.23.1 255.255.255.252 ! router isis passive-interface Loopback0 net 49.0001.1720.1600.2002.00 ! 65 Looking at the show commands R1#show clns neighbor System Id Interface R2 Et0 SNPA 0000.0c47.b947 State Up Holdtime 24 Type Protocol L1L2 IS-IS R1#show clns interface ethernet 0 Ethernet0 is up, line protocol is up Checksums enabled, MTU 1497, Encapsulation SAP Routing Protocol: IS-IS Circuit Type: level-1-2 Interface number 0x0, local circuit ID 0x1 Level-1 Metric: 10, Priority: 64, Circuit ID: R2.01 Number of active level-1 adjacencies: 1 Level-2 Metric: 10, Priority: 64, Circuit ID: R2.01 Number of active level-2 adjacencies: 1 Next IS-IS LAN Level-1 Hello in 5 seconds Next IS-IS LAN Level-2 Hello in 1 seconds Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 66 Looking into the database R2#show clns neighbor System Id Interface SNPA R1 Et0 0000.0c09.9fea R3 Se0 *HDLC* State Up Up R2#show isis database IS-IS Level-1 Link State Database: LSPID LSP Seq Num LSP Checksum R1.00-00 0x0000008B 0x6843 R2.00-00 * 0x00000083 0x276E R2.01-00 * 0x00000004 0x34E1 R3.00-00 0x00000086 0xF30E IS-IS Level-2 Link State Database: LSPID LSP Seq Num LSP Checksum R1.00-00 0x00000092 0x34B2 R2.00-00 * 0x0000008A 0x7A59 R2.01-00 * 0x00000004 0xC3DA R3.00-00 0x0000008F 0x0766 Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. Holdtime 24 28 Type Protocol L1L2 IS-IS L1L2 IS-IS LSP Holdtime 55 77 57 84 ATT/P/OL 0/0/0 0/0/0 0/0/0 0/0/0 LSP Holdtime 41 115 50 112 ATT/P/OL 0/0/0 0/0/0 0/0/0 0/0/0 67 Looking into the Database Detail R2#show isis database R2.00-00 detail IS-IS Level-1 LSP R2.00-00 LSPID LSP Seq Num LSP Checksum LSP Holdtime R2.00-00 * 0x00000093 0x077E 71 Area Address: 49.0001 NLPID: 0xCC Hostname: R2 IP Address: 172.16.2.2 Metric: 10 IP 172.16.12.0 255.255.255.0 Metric: 0 IP 172.16.2.2 255.255.255.255 Metric: 10 IP 172.16.23.0 255.255.255.252 Metric: 10 IS R2.01 Metric: 10 IS R3.00 IS-IS Level-2 LSP R2.00-00 LSPID LSP Seq Num LSP Checksum LSP Holdtime R2.00-00 * 0x0000009A 0x5A69 103 Area Address: 49.0001 NLPID: 0xCC Hostname: R2 IP Address: 172.16.2.2 Metric: 10 IS R2.01 Metric: 10 IS R3.00 Metric: 10 IP 172.16.23.0 255.255.255.252 Metric: 10 IP 172.16.1.1 255.255.255.255 Metric: 10 IP 172.16.3.3 255.255.255.255 Metric: 0 IP 172.16.2.2 255.255.255.255 Metric: 10 IP 172.16.12.0 255.255.255.0 Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. ATT/P/OL 0/0/0 ATT/P/OL 0/0/0 68 Looking into the routing-table R1#show ip route isis i L1 172.16.2.2/32 [115/10] via 172.16.12.2, Ethernet0 i L1 172.16.3.3/32 [115/20] via 172.16.12.2, Ethernet0 R2#show ip route isis Presentation_ID I L1 172.16.1.1/32 [115/10] via 172.16.12.1, Ethernet0 i L1 172.16.3.3/32 [115/10] via 172.16.23.2, Serial0 © 2002, Cisco Systems, Inc. All rights reserved. 69 Presentation_ID © 2002, Cisco Systems, Inc. All rights reserved. 70