Download to read offline
![IS-IS PART 1 packetlife.net
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 area
Condensed Area
Level 2 Backbone between areas
Example 47 0005.80ff.f800.0000 0001 0000.0c00.1234 00
Level 3 Inter-AS routing
Interdomain Part (IDP) Terminology
Portion of the address used in routing between autonomous
Type-Length-Value (TLV)
systems; assigned by ISO
Variable-length modular datasets
Domain-Specific Part (DSP)
Link State PDU (LSP)
Portion of the address relevant only within the local AS
Carry TLVs encompassing link state
Authority and Format Identifier (AFI) information
Identifies the authority which dictates the format of the address Sequence Number Packet (SNP)
Used to request and advertise LSPs; can
Initial Domain Identifier (IDI)
be complete (CSNP) or partial (PSNP)
An organization belonging to the AFI
Hello Packet
High Order DSP (HODSP) Establishes and maintains neighbor
The area within the AS adjacencies
System ID Designated Intermediate System
Unique router identifier; 48 bits for Cisco devices (often taken from A pseudonode responsible for emulating
a MAC address) point-to-point links across a multi-access
NSAP Selector (SEL) segment
Identifies 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 Election
show ip route show isis spf-log Highest-priority interface elected
show ip protocols debug isis spf-events Highest SNPA (MAC/DLCI) breaks tie
show [clns|isis] neighbor debug isis adjacencies-packets Highest system ID breaks SNPA tie
show [clns|isis] interface debug isis spf-statistics Default interface priority is 64
show isis database debug isis update-packets Current DIS may be preempted
by Jeremy Stretch v2.0](https://image.slidesharecdn.com/is-is-130211054220-phpapp01/75/Is-is-1-2048.jpg)
Uploaded bySwapnil Kapate
Is is
IS-IS is a link-state interior gateway protocol used to route within an autonomous system (AS). It uses Dijkstra's shortest path first algorithm to calculate routes. IS-IS has three routing levels - Level 1 routes within an area, Level 2 routes between areas, and Level 3 routes between autonomous systems. Routers establish adjacencies by exchanging Hello packets and link state packets (LSPs) containing topology information in type-length-value (TLV) fields.
More Related Content
Is is
- 1. IS-IS PART 1 packetlife.net 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 area Condensed Area Level 2 Backbone between areas Example 47 0005.80ff.f800.0000 0001 0000.0c00.1234 00 Level 3 Inter-AS routing Interdomain Part (IDP) Terminology Portion of the address used in routing between autonomous Type-Length-Value (TLV) systems; assigned by ISO Variable-length modular datasets Domain-Specific Part (DSP) Link State PDU (LSP) Portion of the address relevant only within the local AS Carry TLVs encompassing link state Authority and Format Identifier (AFI) information Identifies the authority which dictates the format of the address Sequence Number Packet (SNP) Used to request and advertise LSPs; can Initial Domain Identifier (IDI) be complete (CSNP) or partial (PSNP) An organization belonging to the AFI Hello Packet High Order DSP (HODSP) Establishes and maintains neighbor The area within the AS adjacencies System ID Designated Intermediate System Unique router identifier; 48 bits for Cisco devices (often taken from A pseudonode responsible for emulating a MAC address) point-to-point links across a multi-access NSAP Selector (SEL) segment Identifies 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 Election show ip route show isis spf-log Highest-priority interface elected show ip protocols debug isis spf-events Highest SNPA (MAC/DLCI) breaks tie show [clns|isis] neighbor debug isis adjacencies-packets Highest system ID breaks SNPA tie show [clns|isis] interface debug isis spf-statistics Default interface priority is 64 show isis database debug isis update-packets Current DIS may be preempted by Jeremy Stretch v2.0
- 2. IS-IS PART 2 packetlife.net TLV Types Name Use Name Use Name Use 1 Area Addresses Hello, LSP 6 IS Neighbors Hello, L2 LSP 128 IP Internal Reach. LSP 2 IS Neighbors LSP 8 Padding Hello 129 Protocols Supported Hello, LSP 3 ES Neighbors L1 LSP 9 LSP Entries SNP 131 IDRPI SNP, L2 LSP 5 Prefix Neighbors L2 LSP 10 Authentication All 132 IP Interface Address Hello, LSP Configuration Example Area 1 Router A2 192.168.1.0/24 interface FastEthernet0/0 description Area 1 ip address 192.168.1.2 255.255.255.0 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. 192.168.2.0/24 192.168.3.0/24 10 30 description Area 2 ip address 192.168.2.2 255.255.255.0 ip router isis B2 C2 isis circuit-type level-1 10.0.0.8/30 ! B1 C1 router isis B3 net 49.0002.0000.0000.00b2.00 C3 Router A1 Router B1 interface FastEthernet0/0 interface FastEthernet0/0 description Area 1 description Area 2 ip address 192.168.1.1 255.255.255.0 ip address 192.168.2.1 255.255.255.0 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 10.0.0.1 255.255.255.252 ip address 10.0.0.2 255.255.255.252 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 10.0.0.5 255.255.255.252 ip address 10.0.0.9 255.255.255.252 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 49.0002.0000.0000.00b1.00 by Jeremy Stretch v2.0