Home Routing ISIS ISIS protocol study summary

- Link state protocol
- Large ISP used it
- Use Dijkstra's SPF alorithm to calculate OSI route.
- use Partia Route Calculation for IP routes (much effiecient than SPF)
- use "Default metric" (1 ~ 63), VS OSPF use bandwidth
- OSI addressing
- No need backbone area, but use Level
- It was developed by OSI model. and it was design for OSI and well fit to the model
- Integrated ISIS support TCP/IP model(carrying tcp/ip info).. and it was well fit to TCP/IP so.. Very litter modification requires for IPv6. 

## OSI address ##

- Hexadecimal
- Reading right to left
- Three parts
    - Area ID (Veriable length)
    - System ID (6 Bytes), it need to be unique, it can be MAC address.
    - NSEL(1Byt)

    - 49.0003.1111.2222.3333.00
    00 = NSEL
    1111.2222.3333 = System ID
    49.0003 = Area ID

    - 49.0141.4176.1AB2.FE00.63c9.00
    - 49.0005.1111.1111.1111.00

** 49. is private range

## Routing table

IS-IS Routing maintains two IP routing databases
 - Level 1 database : includes Intra-area routes
 - Level 2 database : includes Backbone routes

Router can be L1, L2 or L1/L2

## Configuration

1. Enable IS-IS on the router
    * automatically create L1 and L2 database, unless create is-type.
    ** if you are not tagging, default is "0"
    Router(config)# router isis
    Router(config-router)# net 49.0001.1111.1111.1111.00

2. Configure single OSI address per each router

3. Enable ISIS on per interface basis

    ** sending both L1/L2 hello packet to interface which is enable ISIS
    *** Default metric 10, which is lower than Rip

    Router(config)# interface serial1/0
    Router(config-if)# ip router isis

4. Summary

summary-address level 1 or level 2 or level 1/2 ; have to specify what database will be updated.

5. Redistribute
    - To redistrubte ISIS to other protocol, network that is directly connected couldn't be redistrubuted... so use redistrubte connected with route-map to block some of route that doesn't want to redistrubte.


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