Shulou(Shulou.com)06/01 Report--

IS-IS (Intermediate System-to-Intermediate System, intermediate system to intermediate system)

Address of the ISIS router:

NET-network entity titile, network entity identifier

NET: area + system-id + sel (selector)

And the entire address is represented in hexadecimal.

And the SEL in it is always 0

For example:

0000.0000.0001. 00

Features:

1. It's all represented by hexadecimal.

two。 Must start with 1 byte; and always 49

3. Must end with 1 byte; and always be 0

4. Where the system-id must be a fixed 6 bytes

5. The rest is called "regional ID".

The 6.NET address ranges from 8 bytes to 20 bytes

7. Multiple NET addresses can be configured on a device at the same time, and SID is required to be the same

ISIS message-OSPF message comparison:

Hello-Hello

LSP-LSU

CSNP-DBD

PSNP-LSR and LSAck

ISIS hello: sends hello via multicast, commonly known as IIH

-Type:

LAN IIH, the Hello sent in the broadcast network environment

P2P IIH, Hello sent in a point-to-point network environment

Level-1 hello, using the multicast address 0180-c200-0014

Level-2 hello, using the multicast address 0180-c200-0015

DIS, which is the equivalent of DR in OSPF, is called "designated intermediate system".

Commonly known as "virtual node"

Types of networks supported by ISIS:

P2P

MA/Broadcast

The state established by the ISIS neighbor:-init-- received the hello sent by the other party, but did not find his own SID in it;-up-- received the hello sent by the other party and found his own SID in it. Equivalent to two-way in OSPF. -down-within a certain period of time, the hello packet sent by the other party is not received; the type of ISIS router

Level-1 Router-equivalent to a non-backbone router in OSPF

Level-2 Router-equivalent to the backbone Router in OSPF

Level-1-2 Router-equivalent to ABR in OSPF

Area type of ISIS:

Backbone area-Level-2 area

That is, the neighbor relationship between all routers in the area must be Level-2.

Non-backbone area-that is, Level-1 area

That is, the neighbor relationship between all routers in the area must be Level-1.

Principles:

All Level-1 must be directly connected to Level-2

Configuration commands:

[R1] isis

[enter Isis process-default is 1]

[R1-isis-1] network-entity 49.0012.0000.0000.1111.00

[declared configured network segment]

[R1-gi0/0/0] isis enable 1

[enable Isis on the interface]

Note:

By default, after Huawei runs ISIS, the device level-system-level of each device is

Level-1-2 "

So the type of message sent on each port contains both level-1 and level-2

So, by default, there are 2 neighbor relationships with other routers in the same area; [R1-isis-1] is-level level-1

[change link type]

[R1-gi0/0/0] isis circuit-level level-1

[change system level, default is level-1-2]

[R1] display isis peer

[view Isis neighbors]

[R1] display isis interface gi0/0/0

[view the Isis of this API]

[R1] display isis brief

[view Isis profile]

[R1] display isis lsdb

[view local device Isis database]

Isis database:

It contains a large number of LSP (link state PDU)

Every ISIS router calculates routes based on LSP

When a database in ISIS organizes LSP entries, it is organized based on the type of region, that is, the ISIS database is divided into two categories at most:

Database entries for Level-1 and database entries for Level-2

Special tag bits in LSP:

ATT, which is Attached, or association. Indicates whether the router that generated the LSP is connected to the backbone area.

If 0, it is not connected to the backbone area.

If 1, it is connected to the backbone area.

Then the Level-1 router that receives the LSP will generate a default route for the level-1 to the generating router of the LSP.

LSP with an ATT of 1 can only be generated by a Level-1-2 router

P, which represents Partition, that is, a discontinuous non-backbone region. Always 0 in ISIS

OL,over-load, which means overload. That is, the router that generated the LSP has insufficient resources.

So the router that receives the LSP will not use the router that generated the LSP as the next hop of the route

Transmission of LSP in ISIS:

Level-1- > level-2 defaults to 1 to 2

Level-2- > level-1 defaults to 2 that cannot reach 1

If we want Level-2 routes to enter the level-1 area, we need to use the following command:

[R2] isis

[R1-isis-1] import-route isis level-2 into level-1

This behavior of level-2 entering the level-1 area is called "routing *" or "route leakage".

The purpose is to get the router in the level-1 area to choose the best data forwarding to the target device.

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