IS-IS

IS-IS is implemented as a deterministic routing model for topologies that need link-state behaviour outside OSPF. The current scope is routing correctness for common lab scenarios, not full protocol packet reproduction.

Support level

Area	Level	Notes
IS-IS process	Behaviour model	Process, NET/system ID, and interface membership are represented.
Level-1 / Level-2	Partial	Level concepts are stored and affect the solver where implemented.
SPF route solving	Supported	Computes routes from the modelled IS-IS graph.
IPv4 reachability	Supported	Common training cases.
Advanced TE	Not modelled	MPLS-TE extensions are not represented in depth.

Standards coverage

Standard	Coverage	Notes
ISO/IEC 10589	Behaviour model	Core IS-IS routing concepts.
RFC 1195	Behaviour model	Integrated IS-IS for IP reachability.

Feature matrix

Feature	Status	Notes
router isis	Supported	Creates the process.
net <nsap>	Supported	Sets area/system identity.
Interface participation	Supported	Enables IS-IS on interfaces.
Metric	Partial	Interface metric can affect route choice where parsed.
Authentication	Not modelled	Packet authentication is not a support claim.
Route leaking	Not modelled	Detailed L1/L2 leaking controls are planned for later.

Vendor command matrix

Command	IOS-style	Junos-style	VyOS-style	Notes
router isis CORE	Supported	Partial	Partial	Canonical process.
net 49.0001.0000.0000.0001.00	Supported	Partial	Partial	NET/system ID.
ip router isis CORE	Supported	n/a	n/a	Interface activation.
show isis neighbors	Supported	Partial	Partial	Model-derived adjacency view.
show ip route isis	Supported	Partial	Partial	IS-IS routes.

Behaviour notes

IS-IS SPF is computed deterministically from the configured graph. The model is best suited for route-selection and reachability questions.

Examples

Canonical example

configure terminal
router isis CORE
 net 49.0001.0000.0000.0001.00
interface GigabitEthernet0/0
 ip router isis CORE
end
show isis neighbors
show ip route isis

Vendor styles

IOS-style

router isis CORE
 net 49.0001.0000.0000.0001.00
interface GigabitEthernet0/0
 ip router isis CORE

Junos-style

set interfaces ge-0/0/0 unit 0 family iso
set protocols isis interface ge-0/0/0.0
set protocols isis level 2 wide-metrics-only

VyOS-style

set protocols isis net 49.0001.0000.0000.0001.00
set protocols isis interface eth0

Known limits

Wide metric edge cases, route leaking policy, authentication, DIS election packet detail, and traffic-engineering TLVs are not fully modelled.