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.. include:: /_include/need_improvement.txt
.. _isis:
#####
IS-IS
#####
:abbr:`IS-IS (Intermediate System to Intermediate System)` is a link-state interior gateway routing protocol.
Like OSPF, IS-IS runs the Dijkstra shortest-path first (SPF) algorithm to create a database of the network’s
topology and, from that database, to determine the best (that is, shortest) path to a destination.
The routers exchange topology information with their nearest neighbors.
IS-IS runs directly on the data link layer (Layer 2).
IS-IS addresses are called :abbr:`NETs (Network Entity Titles)` and can be 8 to 20 bytes long, but are generally 10 bytes long.
For example :abbr:`NET (Network Entity Title)`
.. code-block:: none
49.0001.1921.6800.1002.00
The IS-IS address consists of three parts:
:abbr:`AFI (Address family authority identifier)`
``49`` The AFI value 49 is what IS-IS uses for private addressing.
Area identifier:
``0001`` IS-IS area number (Area1)
System identifier:
``1921.6800.1002`` For system idetifier we recommend to use IP address or MAC address of the router.
NET selector:
``00`` Must always be 00, to indicate "this system".
Simple IS-IS configuration using 2 nodes and redistributing connected interfaces.
**Node 1:**
.. code-block:: none
set interfaces dummy dum0 address '203.0.113.1/24'
set interfaces ethernet eth1 address '192.0.2.1/24'
set policy prefix-list EXPORT-ISIS rule 10 action 'permit'
set policy prefix-list EXPORT-ISIS rule 10 prefix '203.0.113.0/24'
set policy route-map EXPORT-ISIS rule 10 action 'permit'
set policy route-map EXPORT-ISIS rule 10 match ip address prefix-list 'EXPORT-ISIS'
set protocols isis FOO interface eth1
set protocols isis FOO net '49.0001.1921.6800.1002.00'
set protocols isis FOO redistribute ipv4 connected level-2 route-map 'EXPORT-ISIS'
**Node 2:**
.. code-block:: none
set interfaces ethernet eth1 address '192.0.2.2/24'
set protocols isis FOO interface eth1
set protocols isis FOO net '49.0001.1921.6800.2002.00'
Show ip routes on Node2:
.. code-block:: none
vyos@r2:~$ show ip route isis
Codes: K - kernel route, C - connected, S - static, R - RIP,
O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP,
F - PBR, f - OpenFabric,
> - selected route, * - FIB route, q - queued route, r - rejected route
I 203.0.113.0/24 [115/10] via 192.0.2.1, eth1, 00:03:42
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