ODC112017 Adjacency Relationship of IS-IS Protocol ISSUE1.00 (2).ppt

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Adjacency Relationship of
IS-IS Protocol

HUAWEI TECHNOLOGIES CO., LTD. All rights reserved Page 2
To calculate the route, IS-IS routers are first
required to discover the neighbors and form the
adjacencies relationship.
The adjacency formation process might vary
according to the different network types; the type of
adjacency relationship formed might vary according to
the different area configuration and router type.

Upon completion of the course, you will be
able to：
Master the concept of area, router type and adjacency
relationship
Understand The adjacency formation process on
point to point link
Understand The adjacency formation process on
broadcast network

Chapter 1 Area, Router Type, and Adjacencies
Chapter 2 Adjacency Relationship Establishment
Chapter 3 Adjacency Relationship Configuration

Neighbor Relationship and Adjacency Relationship
 Neighbor Relationship and Adjacency Relationship
Neighbor relationship：Two ends of the routers of a link are aware
of the existence of each other and they are able to exchange the
protocol packets, such as hello packets, and do not exchange
LSDB.
Adjacency relationship：A relationship formed between neighboring
routers for exchanging routing information.

Identifier
 Before establish any type of adjacency relationship with any neighbor,
the identifiers required are as follow:
Identify every IS (SYSTEM ID)
Identify the area every IS belonged to (AREA ID）
Identify the IS type

NSAP and NET
 NSAP：Network Service Access Point，correspond to CLNP address of
the OSI network layer（similar to the concept of IP address）
 NET：Network Entity Titles，is a special NSAP address
N-selector value 0 indicates that provides service to the network layer
NET is the identifier of the network equipment itself in OSI protocol
stack
High Order DSP
DSP
System ID NSEL
IDI
AFI
IDP
Area ID (1~13B) 6B 1B

49.0021 . 1921.6800.1001 . 00
AreaID SystemID N-SEL
88.0001.0755 . 000f.e225.da08. 00
AreaID SystemID N-SEL
Example of NET

Configuration of SYSTEM ID and AREA ID
 ISs that have the same Area ID belong to the same area.
RTB
RTA
RTC
[RTA]display current-configuration
isis 1
network-entity 49.0001.0000.0000.0001.00
[RTB]display current-configuration
isis 1
network-entity 49.0002.0000.0000.0002.00
[RTC]display current-configuration
isis 1
network-entity 49.0002.0000.0000.0003.00
AREA 49.0002
AREA 49.0001

IS type, Circuit-level type and adjacency type
 3 types of IS
Level-1, Level-2, Level-1-2
 3 types of circuit level
 3 types of adjacency relationship

IS type and Adjacency type
 The combinations below can form adjacencies（ in same area）
L1 L1
L1
L2 L2
L2
L12 L12
L12
L1 L12
L1
L2 L12
L2

IS type and Adjacency type
 The combinations below can form adjacencies（ in different area）
L2 L2
L2
L12 L12
L2
L2 L12
L2

Conditions for adjacency establishment
 To establish IS-IS adjacency relationship, the following criteria must be
satisfied:
Only the same level neighboring routers can form adjacency
The Area ID must be the same for Level-1 router
Satisfy the network segment checking. By default network segment
must be the same to form neighbor relationship and adjacency

Adjacency Relationship and Network Type
 Adjacency relationship establishment varies according to the network
types
 IS-IS supports two network types
 Point to Point network
− PPP, HDLC and so on
− NBMA network is recommended to be configured as PPP
network.
Broadcast Network
− Ethernet, Token Ring and so on

HELLO Packet
 IS-IS establishes the adjacency relationship via Hello packet.
 IS-IS Hello Packets (IIH)
Level 1 LAN IS-IS Hello
Level 2 LAN IS-IS Hello
Point-to-point Hello

The Packet Format of Point-to-Point IIH
Intradomain Routing Protocol Discriminator
1B
Length Indicator 1B
Version/Protocol ID extension
1B
ID Length 1B
R R R PDU Type 1B
Version 1B
Reserved 1B
Maximum Area Addresses 1B
Common Fixed Header 8B
Reserved (6 bits) Circuit Type (2 bits) 1B
Source ID 6B
Holding Time
2B
PDU Length
2B
Local Circuit ID 1B
TLV Fields (Variable length)

Adjacency Relationship in Point to Point Link
SYSTEM ID : 0000.0000.0002
SYSTEM ID: 0000.0000.0001
SYSTEM TYPE: Unknown
Adjacencystate: Initialising
SYSTEM TYPE：IS
Adjacencystate: up
ISH
SYSTEM TYPE: Unknown
ISH
IIH
IIH
SYSTEM TYPE：IS
Adjacencystate: up

The Packet Format of LAN IIH
Intradomain Routing Protocol Discriminator
1B
Length Indicator 1B
Version/Protocol ID Extension 1B
ID Length 1B
R R R PDU Type 1B
Version 1B
Reserved 1B
Maximun Area Addresses 1B
Common Fixed Header 8B
Reserved (6bits) Circuit Type(2bits) 1B
Source ID 6B
Holding Time
2B
PDU Length
2B
R Priority 1B
LAN ID 7B
TLV

Adjacency Relationship in Broadcast Network
SYSTEM ID : 0000.0000.0002
SYSTEM ID: 0000.0000.0001
Adjacencystate: up
IIH: neighbour=0000.0000.0002
IIH: neighbour=0000.0000.0001
Adjacencystate: up
IIH: neighbour=NULL
IIH: neighbour=NULL

Adjacency Relationship Configuration
RTB
RTA
L12 L12
49.0001.0000.0000.0004.00
RTC
RTD L12 L12
49.0002.0000.0000.0003.00
49.0002.0000.0000.0002.00
49.0001.0000.0000.0001.00
E0
E0
S0 S0
S1
S1
23.23.23.0/30
10.10.10.0/24
12.12.12.0/30

Enable IS-IS and Configure NET
RTB
RTA
RTC
RTD
[RTA]isis
[RTA-isis-1]network-entity 49.0001.0000.0000.0001.00
[RTA]interface LoopBack 0
[RTA-LoopBack0]isis enable
[RTA]interface Serial 0
[RTA-Serial0]isis enable
[RTA]interface Ethernet 0
[RTA-Ethernet0]isis enable
S0 S0
S1
S1
E0
E0

Display the Adjacencies Relationship
[RTA]display isis peer
System Id Interface Circuit Id State HoldTime Type PRI
0000.0000.0002 S0 002 Up 27s L2 --
0000.0000.0004 Eth0 0000.0000.0004.02 Up 6s L1(L1L2) 64
0000.0000.0004 Eth0 0000.0000.0004.02 Up 6s L2(L1L2) 64
[RTB]display isis peer
0000.0000.0001 S0 002 Up 22s L2 --
0000.0000.0003 S1 003 Up 28s L1L2 --
[RTC]display isis peer
0000.0000.0002 S1 002 Up 26s L1L2 --
[RTD]display isis peer
0000.0000.0001 Eth0 0000.0000.0004.02 Up 23s L1(L1L2) 64
0000.0000.0001 Eth0 0000.0000.0004.02 Up 23s L2(L1L2) 64

Change the IS Type
RTB
RTA
RTC
RTD
[RTD]isis
[RTD-isis-1]is-level level-2
S0 S0
S1
S1
E0
E0
[RTC]isis
[RTC-isis-1]is-level level-1

Display the Adjacencies Relationship
[RTA]display isis peer
0000.0000.0002 S0 002 Up 21s L2 --
0000.0000.0004 Eth0 0000.0000.0004.02 Up 8s L2 64
[RTB]display isis peer
0000.0000.0001 S0 002 Up 26s L2 --
0000.0000.0003 S1 003 Up 24s L1 --
[RTC]display isis peer
0000.0000.0002 S1 002 Up 22s L1 --
[RTD]display isis peer
0000.0000.0001 Eth0 0000.0000.0004.02 Up 20s L2 64

Observe the IIH Packets
<RTA>debugging isis adjacency
*0.16417515 RTA ISIS/7/ISIS:
ISIS-1-ADJ: Sending Lan L2 Hello on Eth0.
*0.16418484 RTA ISIS/7/ISIS:

Change the Interface Circuit-level
RTB
RTA
RTC
RTD
[RTA]interface Ethernet 0
[RTA-Ethernet0]isis circuit-level level-2
S0 S0
S1
S1
E0
E0

Observe the IIH packets
<RTA>debugging isis adjacency
*0.17445797 RTA ISIS/7/ISIS:
[RTA]display isis interface
Interface information for ISIS(1)
---------------------------------
Interface Id IPV4.State MTU Type DR
Loop0 001 Up 1500 L1/L2 --
S0 002 Up 1500 L1/L2 --
Eth0 003 Up 1497 L2 No

Conclusion
 How many types of IS-IS routers are
there？
 How many types of IS-IS
adjacencies relationship are there?
 Describe the corresponding between
the type of IS-IS router and the type
of adjacency relationship.
 Describe the difference in the
process of adjacency relationship
establishment between Point to
Point link and broadcast network.

ODC112017 Adjacency Relationship of IS-IS Protocol ISSUE1.00 (2).ppt

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