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Is is

  1. 1. IS-IS PART 1 Protocol Header Attributes 4 8 12 16 Type Link-State IRPD Packet Length Algorithm Dijkstra Version/Protocol ID Extension ID Length Metric Default (10) R R R PDU Type Version AD 115 Reserved Maximum Area Addresses Standard ISO 10589 Type Length Protocols IP, CLNS Value ... Transport Layer 2 NSAP Addressing Authentication Plaintext, MD5 Interdomain Part Domain-Specific Part Routing Levels Level 0 Used to locate end systems NSAP AFI IDI HODSP System ID SEL Level 1 Routing within an areaCondensed Area Level 2 Backbone between areas Example 47 0005.80ff.f800.0000 0001 0000.0c00.1234 00 Level 3 Inter-AS routingInterdomain Part (IDP) TerminologyPortion of the address used in routing between autonomous Type-Length-Value (TLV)systems; assigned by ISO Variable-length modular datasetsDomain-Specific Part (DSP) Link State PDU (LSP)Portion of the address relevant only within the local AS Carry TLVs encompassing link stateAuthority and Format Identifier (AFI) informationIdentifies the authority which dictates the format of the address Sequence Number Packet (SNP) Used to request and advertise LSPs; canInitial Domain Identifier (IDI) be complete (CSNP) or partial (PSNP)An organization belonging to the AFI Hello PacketHigh Order DSP (HODSP) Establishes and maintains neighborThe area within the AS adjacenciesSystem ID Designated Intermediate SystemUnique router identifier; 48 bits for Cisco devices (often taken from A pseudonode responsible for emulatinga MAC address) point-to-point links across a multi-accessNSAP Selector (SEL) segmentIdentifies a network layer service; always 0x00 in a NET address Adjacency Requirements Network Types Interface MTUs must match Broadcast Point-to-Point Levels must match DIS Elected Yes No Areas must match (if level 1) Neighbor Discovery Yes Yes System IDs must be unique Hello/Dead Timers 10/30 10/30 Authentication must succeed Troubleshooting DIS Electionshow ip route show isis spf-log Highest-priority interface electedshow ip protocols debug isis spf-events Highest SNPA (MAC/DLCI) breaks tieshow [clns|isis] neighbor debug isis adjacencies-packets Highest system ID breaks SNPA tieshow [clns|isis] interface debug isis spf-statistics Default interface priority is 64show isis database debug isis update-packets Current DIS may be preemptedby Jeremy Stretch v2.0
  2. 2. IS-IS PART 2 TLV Types Name Use Name Use Name Use1 Area Addresses Hello, LSP 6 IS Neighbors Hello, L2 LSP 128 IP Internal Reach. LSP2 IS Neighbors LSP 8 Padding Hello 129 Protocols Supported Hello, LSP3 ES Neighbors L1 LSP 9 LSP Entries SNP 131 IDRPI SNP, L2 LSP5 Prefix Neighbors L2 LSP 10 Authentication All 132 IP Interface Address Hello, LSP Configuration Example Area 1 Router A2 interface FastEthernet0/0 description Area 1 ip address A3 ip router isis A2 isis circuit-type level-1 ! router isis A1 net 49.0001.0000.0000.00a2.00 10 0 /3 .0 Router B2 .0 .0 Area 2 Area 3 0 .4/ interface FastEthernet0/0 .0. 10 30 description Area 2 ip address ip router isis B2 C2 isis circuit-type level-1 ! B1 C1 router isis B3 net 49.0002.0000.0000.00b2.00 C3 Router A1 Router B1interface FastEthernet0/0 interface FastEthernet0/0 description Area 1 description Area 2 ip address ip address ip router isis ip router isis isis circuit-type level-1 isis circuit-type level-1! !interface Serial1/0 interface Serial1/0 no ip address no ip address encapsulation frame-relay encapsulation frame-relay! !interface Serial1/0.1 point-to-point interface Serial1/0.1 point-to-point description To Area 2 description To Area 1 ip address ip address ip router isis ip router isis isis circuit-type level-2-only isis circuit-type level-2-only! MD5 authentication (keychain not shown) ! MD5 authentication (keychain not shown) isis authentication mode md5 isis authentication mode md5 isis authentication key-chain <keychain> isis authentication key-chain <keychain> frame-relay interface-dlci 101 frame-relay interface-dlci 101! !interface Serial1/0.2 point-to-point interface Serial1/0.2 point-to-point description To Area 3 description To Area 3 ip address ip address ip router isis ip router isis isis circuit-type level-2-only isis circuit-type level-2-only frame-relay interface-dlci 102 frame-relay interface-dlci 103! !router isis router isis net 49.0001.0000.0000.00a1.00 net 49.0002.0000.0000.00b1.00by Jeremy Stretch v2.0