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IS-IS

IS-IS is a link-state interior gateway routing protocol which is described in ISO10589, RFC 1195, RFC 5308. 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 NETs and can be 8 to 20 bytes long, but are generally 10 bytes long.

For example NET

49.0001.1921.6800.1002.00

The IS-IS address consists of three parts:

AFI
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”.

General Configuration

set protocols isis <name> net <network-entity-title>
This command enables the ISIS process by specifying the ISIS domain with ‘name’. ISIS implementation does not yet support multiple ISIS processes but you must specify the name of ISIS process. This commad also sets network entity title (NET) provided in ISO format.
set protocols isis <name> interface <interface>
This command activates ISIS adjacency on this interface. Note that the name of ISIS instance must be the same as the one used to configure the ISIS process.
set protocols isis <name> dynamic-hostname
This command enables support for dynamic hostname. Dynamic hostname mapping determined as described in RFC 2763, Dynamic Hostname Exchange Mechanism for IS-IS.
set protocols isis <name> level <level-1|level-1-2|level-2>

This command defines the ISIS router behavior:

level-1 Act as a station router only. level-1-2 Act as both a station router and an area router. level-2-only Act as an area router only.
set protocols isis <name> lsp-mtu <size>
This command configures the maximum size of generated LSPs, in bytes. The size range is 128 to 4352.
set protocols isis <name> metric-style <narrow|transition|wide>

This command sets old-style (ISO 10589) or new-style packet formats:

narrow Use old style of TLVs with narrow metric. transition Send and accept both styles of TLVs during transition. wide Use new style of TLVs to carry wider metric.
set protocols isis <name> purge-originator
This command enables RFC 6232 purge originator identification. Enable purge originator identification (POI) by adding the type, length and value (TLV) with the Intermediate System (IS) identification to the LSPs that do not contain POI information. If an IS generates a purge, VyOS adds this TLV with the system ID of the IS to the purge.
set protocols isis <name> set-attached-bit
This command sets ATT bit to 1 in Level1 LSPs. It is described in RFC 3787.
set protocols isis <name> set-overload-bit
This command sets overload bit to avoid any transit traffic through this router. It is described in RFC 3787.
set protocols isis name default-information originate <ipv4|ipv6> level-1
This command will generate a default-route in L1 database.
set protocols isis name default-information originate <ipv4|ipv6> level-2
This command will generate a default-route in L2 database.

Interfaces Configuration

set protocols isis <name> interface <interface> circuit-type <level-1|level-1-2|level-2-only>

This command specifies circuit type for interface:

level-1 Level-1 only adjacencies are formed. level-1-2 Level-1-2 adjacencies are formed level-2-only Level-2 only adjacencies are formed
set protocols isis <name> interface <interface> hello-interval <seconds>
This command sets hello interval in seconds on a given interface. The range is 1 to 600.
set protocols isis <name> interface <interface> hello-multiplier <seconds>
This command sets multiplier for hello holding time on a given interface. The range is 2 to 100.
set protocols isis <name> interface <interface> hello-padding
This command configures padding on hello packets to accommodate asymmetrical maximum transfer units (MTUs) from different hosts as described in RFC 3719. This helps to prevent a premature adjacency Up state when one routing device’s MTU does not meet the requirements to establish the adjacency.
set protocols isis <name> interface <interface> metric <metric>
This command set default metric for circuit. The metric range is 1 to 16777215 (Max value depend if metric support narrow or wide value).
set protocols isis <name> interface <interface> network point-to-point
This command specifies network type to ‘Point-to-Point’. The default network type is broadcast.
set protocols isis <name> interface <interface> passive
This command configures the passive mode for this interface.
set protocols isis <name> interface <interface> password plaintext-password <text>
This command configures the authentication password for the interface.
set protocols isis <name> interface <interface> priority <number>
This command sets priority for the interface for DIS election. The priority range is 0 to 127.
set protocols isis <name> interface <interface> psnp-interval <number>
This command sets PSNP interval in seconds. The interval range is 0 to 127.
set protocols isis <name> interface <interface> no-three-way-handshake
This command disables Three-Way Handshake for P2P adjacencies which described in RFC 5303. Three-Way Handshake is enabled by default.

Redistribution Configuration

set protocols isis <name> redistribute ipv4 <route source> level-1
This command redistributes routing information from the given route source into the ISIS database as Level-1. There are six modes available for route source: bgp, connected, kernel, ospf, rip, static.
set protocols isis <name> redistribute ipv4 <route source> level-2
This command redistributes routing information from the given route source into the ISIS database as Level-2. There are six modes available for route source: bgp, connected, kernel, ospf, rip, static.
set protocols isis <name> redistribute ipv4 <route source> <level-1|level-2> metric <number>
This command specifies metric for redistributed routes from the given route source. There are six modes available for route source: bgp, connected, kernel, ospf, rip, static. The metric range is 1 to 16777215.
set protocols isis <name> redistribute ipv4 <route source> <level-1|level-2> route-map <name>
This command allows to use route map to filter redistributed routes from the given route source. There are six modes available for route source: bgp, connected, kernel, ospf, rip, static.

Timers Configuration

set protocols isis <name> lsp-gen-interval <seconds>
This command sets minimum interval in seconds between regenerating same LSP. The interval range is 1 to 120.
set protocols isis <name> lsp-refresh-interval <seconds>
This command sets LSP refresh interval in seconds. IS-IS generates LSPs when the state of a link changes. However, to ensure that routing databases on all routers remain converged, LSPs in stable networks are generated on a regular basis even though there has been no change to the state of the links. The interval range is 1 to 65235. The default value is 900 seconds.
set protocols isis <name> max-lsp-lifetime <seconds>
This command sets LSP maximum LSP lifetime in seconds. The interval range is 350 to 65535. LSPs remain in a database for 1200 seconds by default. If they are not refreshed by that time, they are deleted. You can change the LSP refresh interval or the LSP lifetime. The LSP refresh interval should be less than the LSP lifetime or else LSPs will time out before they are refreshed.
set protocols isis <name> spf-interval <seconds>
This command sets minimum interval between consecutive SPF calculations in seconds.The interval range is 1 to 120.
set protocols isis <name> spf-delay-ietf holddown <milliseconds>
set protocols isis <name> spf-delay-ietf init-delay <milliseconds>
set protocols isis <name> spf-delay-ietf long-delay <milliseconds>
set protocols isis <name> spf-delay-ietf short-delay <milliseconds>
set protocols isis <name> spf-delay-ietf time-to-learn <milliseconds>
This commands specifies the Finite State Machine (FSM) intended to control the timing of the execution of SPF calculations in response to IGP events. The process described in RFC 8405.

Configuration Example

Simple IS-IS configuration using 2 nodes and redistributing connected interfaces.

Node 1:

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:

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:

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