1. 111 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID

2. 2 © 2002, Cisco Systems, Inc. All rights reserved. Session Number Presentation_ID Integrated IS-IS Wayne Lewis / Torrey Suzuki

3. 333 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID Agenda ISIS Overview CLNS Addressing ISIS Areas ISIS PDUs LSP Header Flooding Configuration

4. 444 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID Teminology AFIAuthority and Format Identifier (the first octet of all OSI NSAP addresses - identifies format of the rest of the address) CLNPConnection-Less Network Protocol (ISO 8473 - the OSI connectionless network layer protocol - very similar to IP) ESEnd System (The OSI term for a host ) ISIntermediate System (The OSI term for a Router) ES-ISEnd System to Intermediate System Routing exchange protocol (ISO 9542 - OSI protocol between routers and end systems). IS-ISIntermediate System to Intermediate System Routing Exchange Protocol (the ISO protocol for routing within a single routing domain. IS-IS HelloA Hello packet defined by the IS-IS Protocol LSPLink State Packet (a type of packet used by the IS-IS protocol).

5. 555 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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)

6. 666 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

7. 777 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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.

8. 888 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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.

9. 999 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

10. 10 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID CLNS Addressing AreaSystem IDN-SEL CLNS Addressing consists of 3 parts Area – Variable System ID N-SEL(ector)

11. 11 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID NSAPs and Addressing ISO/IEC 10589 distinguishes only 3 fields in the NSAP address format 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) IDP AFI IDI DSP High Order DSP System ID NSEL Variable Length Area Address 6 Bytes1 Byte

12. 12 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

13. 13 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

14. 14 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID CLNS Addressing: AFI Values Address Domain AFI Value X.121 ISO DCC ISO 6523 Local 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

15. 15 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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.

16. 16 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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.

17. 17 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

18. 18 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID CLNS Addressing: NSAP Examples 39.0f01.0003.6666.6666.6666.00 39.0f01.0002.3333.3333.3333.00 39.0f01.0001.2222.2222.2222.00 39.0f01.0001.1111.1111.1111.00 39.0f01.0002.4444.4444.4444.00 39.0f01.0004.7777.7777.7777.00 39.0f01.0004.8888.8888.8888.00

19. 19 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

20. 20 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

21. 21 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

22. 22 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

23. 23 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID Areas and backbone routers L1L2 L1 Area 49.001 Area 49.003 Area 49.0002

24. 24 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID Areas and backbone routers Backbone MUST BE L2 contiguous L1L2 L1-only L2-only L1-only Area-2 Area-1 Area-3 Area-4 L1-only

25. 25 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID Areas and backbone routers area 1 router A area 3 rtr F area 2 rtr D area 2 rtr E area 2 rtr B area 2 rtr 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. “I’m in area 2 and ALL my neighbors are in the same area. I must be a L1-only router ?” !! NO !! Rtr C must have a full L2 LSDB to route between areas 1, 3 and 4. Remember, the backbone must be contiguous. C

26. 26 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

27. 27 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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)

28. 28 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

29. 29 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID ISIS Packet Header Protocol Identifier Header Length Version ID Length Packet Type Version Reserved Max. Area Addresses # of Octets 1 1 1 1 1 1 1 1

30. 30 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID Summary of Packet Types L1 - LAN Hello 15 L2 - LAN Hello 16 Point-to-point Hello 17 L1 LSP 18 L1 CSNP 24 L2 CSNP25 L1 PSNP 26 L2 PSNP 27

31. 31 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID Encapsulation Datalink header (OSI family 0xFEFE) ISIS fixed header (first byte is 0x83) ISIS TLVs ISIS Datalink header (OSI family 0xFEFE) ESIS fixed header (first byte is 0x81) ESIS TLVs ESIS Datalink header (OSI family 0xFEFE) CLNS header (with NSAPs) (first byte is 0x80) User data CLNS

32. 32 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID Mac layer addresses On LANs IS-IS PDUs are forwarded to the following well known MAC layer broadcast 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

33. 33 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID Hello PDUs Common Fixed Header Reserved Source ID Holding Time Packet Length Priority Circuit type ID Length # of Octets 8 1 2 2 1 r LAN ID ID Length + 1 Common Fixed Header Reserved Source ID Holding Time Packet Length Local Circuit ID ID Length # of Octets 8 1 2 2 1 Circuit type Point-to-Point ISIS Hello LAN ISIS Hello

34. 34 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

35. 35 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

36. 36 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

37. 37 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

38. 38 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID Hello PDUs ES sends ESH ISIS adjacency through IIH IS send ISH for ES 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

39. 39 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

40. 40 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID Non-Pseudonode LSP generation Each IS will create and flood a new Non- Pseudonode 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

41. 41 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

42. 42 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID Pseudonode LSP generation PSN DIS 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

43. 43 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID LSPDB without Pseudonode LSP for routerC IS: 10 A 10 B 10 D ES: 10 E LSP for routerB IS: 10 A 10 C 10 D ES: 10 E LSP for routerD IS: 10 A 10 B 10 C ES: 10 E LSP for routerA IS: 10 B 10 C 10 D ES: 10 E endsystem E

44. 44 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID Pseudonode in the LSPDB LSP for routerA IS: 10 P endsystem E LSP for the Pseudonode P IS: 0 A 0 B 0 C 0 D ES: 0 E LSP for routerA IS: 10 P LSP for routerA IS: 10 P LSP for routerA IS: 10 P

45. 45 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

46. 46 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID CSNP Common Fixed Header Start LSP ID End LSP ID ID Length + 1 # of Octets 8 2 ID Length + 2 Source ID Packet Length ID Length + 2

47. 47 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

48. 48 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

49. 49 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

50. 50 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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 PN-ID Frag-Nr

51. 51 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

52. 52 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

53. 53 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

54. 54 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

55. 55 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

56. 56 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

57. 57 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

58. 58 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

59. 59 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

60. 60 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

61. 61 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

62. 62 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID Flooding on a p2p link RTARTBRTC Interface 1 Interface 2Interface 3 Interface 4 PSNP RTA.00-00 SEQ#100 PSNP RTA.00-00 SEQ#100 LSP RTA.00-00 SEQ#100 LSP RTA.00-00 SEQ#100

63. 63 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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

64. 64 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID Flooding on a LAN(Broadcast Links) RTA (DIS)RTB Interface 1 Interface 2 PSNP RTB.00-00 SEQ#200 LSP RTA.00-00 SEQ#100 RTC Interface 3 CSNP LSP RTC.00-00 SEQ#1 RTA RTB RTA

65. 65 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID How to Configure ? R1 R2 R3 s0 e0 ! 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 ! 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 ! R1R2

66. 66 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID Looking at the show commands R1#show clns neighbor System Id Interface SNPA State Holdtime Type Protocol R2 Et0 0000.0c47.b947 Up 24 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

67. 67 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID Looking into the database R2#show clns neighbor System Id Interface SNPA State Holdtime Type Protocol R1 Et0 0000.0c09.9fea Up 24 L1L2 IS-IS R3 Se0 *HDLC* Up 28 L1L2 IS-IS R2#show isis database IS-IS Level-1 Link State Database: LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL R1.00-00 0x0000008B 0x6843 55 0/0/0 R2.00-00 * 0x00000083 0x276E 77 0/0/0 R2.01-00 * 0x00000004 0x34E1 57 0/0/0 R3.00-00 0x00000086 0xF30E 84 0/0/0 IS-IS Level-2 Link State Database: LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL R1.00-00 0x00000092 0x34B2 41 0/0/0 R2.00-00 * 0x0000008A 0x7A59 115 0/0/0 R2.01-00 * 0x00000004 0xC3DA 50 0/0/0 R3.00-00 0x0000008F 0x0766 112 0/0/0

68. 68 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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 ATT/P/OL R2.00-00 * 0x00000093 0x077E 71 0/0/0 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 ATT/P/OL R2.00-00 * 0x0000009A 0x5A69 103 0/0/0 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

69. 69 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID 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 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

70. 70 © 2002, Cisco Systems, Inc. All rights reserved. Presentation_ID