IS-IS

IS-IS (Intermediate System to Intermediate System) is a link-state interior gateway protocol that uses a two-level hierarchical architecture for scalable routing in large enterprise and service provider networks on NX-OS. It supports VRF-aware multi-instance deployments with configurable IS type (L1, L2, L1/L2), NET address assignment, metric styles (narrow, wide, transition), authentication per level, and advanced features like BFD integration and overload bit control. IS-IS interface-level configuration manages circuit type, metric, priority, network type, authentication, passive mode, and hello/hold timers across loopback, VLAN, Ethernet, and port-channel interfaces, and Ethernet and port-channel subinterfaces.

IS-IS (Intermediate System to Intermediate System) is a link-state interior gateway protocol that uses a two-level hierarchical architecture for scalable routing in large enterprise and service provider networks on NX-OS. It supports VRF-aware multi-instance deployments with configurable IS type (L1, L2, L1/L2), NET address assignment, metric styles (narrow, wide, transition), authentication per level, and advanced features like BFD integration and overload bit control. IS-IS interface-level configuration manages circuit type, metric, priority, network type, authentication, passive mode, and hello/hold timers across loopback, VLAN, Ethernet, and port-channel interfaces.

Diagram

Diagram

Classes

nxos

Name	Type	Constraint	Mandatory	Default Value
devices	List	devices	No
device_groups	List	device_groups	No
global	Class	global	No
templates	List	templates	No
interface_groups	List	interface_groups	No

nxos

Name	Type	Constraint	Mandatory	Default Value
devices	List	devices	No
device_groups	List	device_groups	No
global	Class	global	No
templates	List	templates	No

devices (nxos)

Name	Type	Constraint	Mandatory	Default Value
configuration	Class	configuration	No

device_groups (nxos)

Name	Type	Constraint	Mandatory	Default Value
configuration	Class	configuration	No

global (nxos)

Name	Type	Constraint	Mandatory	Default Value
configuration	Class	configuration	No

templates (nxos)

Name	Type	Constraint	Mandatory	Default Value
configuration	Class	configuration	No

interface_groups (nxos)

Name	Type	Constraint	Mandatory	Default Value
configuration	Class	configuration	No

configuration (nxos.devices)

Name	Type	Constraint	Mandatory	Default Value
routing	Class	routing	No
interfaces	Class	interfaces	No

configuration (nxos.interface_groups)

Name	Type	Constraint	Mandatory	Default Value
subinterfaces	List	subinterfaces	No
isis	Class	isis	No

interfaces (nxos.devices.configuration)

Name	Type	Constraint	Mandatory	Default Value
loopbacks	List	loopbacks	No
vlans	List	vlans	No
ethernets	List	ethernets	No
port_channels	List	port_channels	No

ethernets (nxos.devices.configuration.interfaces)

Name	Type	Constraint	Mandatory	Default Value
subinterfaces	List	subinterfaces	No
isis	Class	isis	No

ethernets (nxos.devices.configuration.interfaces)

Name	Type	Constraint	Mandatory	Default Value
isis	Class	isis	No

port_channels (nxos.devices.configuration.interfaces)

Name	Type	Constraint	Mandatory	Default Value
subinterfaces	List	subinterfaces	No
isis	Class	isis	No

port_channels (nxos.devices.configuration.interfaces)

Name	Type	Constraint	Mandatory	Default Value
isis	Class	isis	No

routing (nxos.devices.configuration)

Name	Type	Constraint	Mandatory	Default Value
isis_instances	List	isis_instances	No

loopbacks (nxos.devices.configuration.interfaces)

Name	Type	Constraint	Mandatory	Default Value
isis	Class	isis	No

vlans (nxos.devices.configuration.interfaces)

Name	Type	Constraint	Mandatory	Default Value
isis	Class	isis	No

subinterfaces (nxos.devices.configuration.interfaces.ethernets)

Name	Type	Constraint	Mandatory	Default Value
isis	Class	isis	No

isis_instances (nxos.devices.configuration.routing)

Name	Type	Constraint	Mandatory	Default Value
name	String		Yes
flush_routes	Boolean	true, false	No
isolate	Boolean	true, false	No
shutdown	Boolean	true, false	No
authentication_check_level_1	Boolean	true, false	No
authentication_check_level_2	Boolean	true, false	No
authentication_key_chain_level_1	String		No
authentication_key_chain_level_2	String		No
authentication_type_level_1	Choice	cleartext, md5, unknown	No
authentication_type_level_2	Choice	cleartext, md5, unknown	No
reference_bandwidth	Integer	min: 0, max: 4294967295	No
reference_bandwidth_unit	Choice	mbps, gbps	No
is_type	Choice	level-1, level-2, level-1-2	No
log_adjacency_changes	Boolean	true, false	No
metric_style	Choice	narrow, wide, transition	No
lsp_mtu	Integer	min: 256, max: 4352	No
net	String		No
passive_interface_default	Choice	level-1, level-2, level-1-2, unknown	No
max_lsp_lifetime	Integer	min: 1, max: 65535	No
queue_limit	Integer	min: 200, max: 65535	No
set_overload_bit	Choice	off, always, on-startup, on-startup-wait-for-bgp, on-startup-wait-for-bgp-max-wait	No
set_overload_bit_on_startup	Integer	min: 5, max: 86400	No
set_overload_bit_wait_for_bgp	Integer	min: 0, max: 65535	No
set_overload_bit_suppress	Choice	interlevel, external	No
spf_interval_level_1_max_wait	Integer	min: 50, max: 120000	No
spf_interval_level_1_initial_wait	Integer	min: 50, max: 120000	No
spf_interval_level_1_second_wait	Integer	min: 50, max: 120000	No
spf_interval_level_2_max_wait	Integer	min: 50, max: 120000	No
spf_interval_level_2_initial_wait	Integer	min: 50, max: 120000	No
spf_interval_level_2_second_wait	Integer	min: 50, max: 120000	No
lsp_gen_interval_level_1_max_wait	Integer	min: 50, max: 120000	No
lsp_gen_interval_level_1_initial_wait	Integer	min: 50, max: 120000	No
lsp_gen_interval_level_1_second_wait	Integer	min: 50, max: 120000	No
lsp_gen_interval_level_2_max_wait	Integer	min: 50, max: 120000	No
lsp_gen_interval_level_2_initial_wait	Integer	min: 50, max: 120000	No
lsp_gen_interval_level_2_second_wait	Integer	min: 50, max: 120000	No
graceful_restart	Boolean	true, false	No
graceful_restart_t3_manual	Integer	min: 30, max: 65535	No
address_families	List	address_families	No
vrfs	List	vrfs	No

isis_instances (nxos.devices.configuration.routing)

Name	Type	Constraint	Mandatory	Default Value
name	String		Yes
flush_routes	Boolean	true, false	No
isolate	Boolean	true, false	No
shutdown	Boolean	true, false	No
authentication_check_level_1	Boolean	true, false	No
authentication_check_level_2	Boolean	true, false	No
authentication_key_chain_level_1	String		No
authentication_key_chain_level_2	String		No
authentication_type_level_1	Choice	cleartext, md5, unknown	No
authentication_type_level_2	Choice	cleartext, md5, unknown	No
reference_bandwidth	Integer	min: 0, max: 4294967295	No
reference_bandwidth_unit	Choice	mbps, gbps	No
is_type	Choice	level-1, level-2, level-1-2	No
log_adjacency_changes	Boolean	true, false	No
metric_style	Choice	narrow, wide, transition	No
lsp_mtu	Integer	min: 256, max: 4352	No
net	String		No
passive_interface_default	Choice	level-1, level-2, level-1-2, unknown	No
max_lsp_lifetime	Integer	min: 1, max: 65535	No
queue_limit	Integer	min: 200, max: 65535	No
set_overload_bit	Choice	off, always, on-startup, on-startup-wait-for-bgp, on-startup-wait-for-bgp-max-wait	No
set_overload_bit_on_startup	Integer	min: 5, max: 86400	No
set_overload_bit_wait_for_bgp	Integer	min: 0, max: 65535	No
set_overload_bit_suppress	Choice	interlevel, external	No
address_families	List	address_families	No
vrfs	List	vrfs	No

isis (nxos.devices.configuration.interfaces.loopbacks)

Name	Type	Constraint	Mandatory	Default Value
instance_name	String		Yes
circuit_type	Choice	level-1, level-2, level-1-2	No
ipv4	Boolean	true, false	No
ipv6	Boolean	true, false	No
network_point_to_point	Boolean	true, false	No
passive_interface	Choice	level-1, level-2, level-1-2, no-level-1, no-level-2, no-level-1-2	No
metric_level_1	Integer	min: 0, max: 16777216	No
metric_level_2	Integer	min: 0, max: 16777216	No
ipv6_metric_level_1	Integer	min: 0, max: 16777216	No
ipv6_metric_level_2	Integer	min: 0, max: 16777216	No
priority_level_1	Integer	min: 0, max: 127	No
priority_level_2	Integer	min: 0, max: 127	No
hello_interval	Integer	min: 1, max: 65535	No
hello_interval_level_1	Integer	min: 1, max: 65535	No
hello_interval_level_2	Integer	min: 1, max: 65535	No
hello_multiplier	Integer	min: 3, max: 1000	No
hello_multiplier_level_1	Integer	min: 3, max: 1000	No
hello_multiplier_level_2	Integer	min: 3, max: 1000	No
hello_padding	Choice	always, transient, never	No
authentication_check	Boolean	true, false	No
authentication_check_level_1	Boolean	true, false	No
authentication_check_level_2	Boolean	true, false	No
authentication_key_chain	String		No
authentication_key_chain_level_1	String		No
authentication_key_chain_level_2	String		No
authentication_type	Choice	clear, md5, unknown	No
authentication_type_level_1	Choice	clear, md5, unknown	No
authentication_type_level_2	Choice	clear, md5, unknown	No
mtu_check	Boolean	true, false	No
mtu_check_level_1	Boolean	true, false	No
mtu_check_level_2	Boolean	true, false	No
bfd	Boolean	true, false	No
ipv6_bfd	Boolean	true, false	No
csnp_interval_level_1	Integer	min: 1, max: 65535	No
csnp_interval_level_2	Integer	min: 1, max: 65535	No
lsp_interval	Integer	min: 10, max: 65535	No
retransmit_interval	Integer	min: 1, max: 65535	No
retransmit_throttle_interval	Integer	min: 20, max: 65535	No
mesh_group	Integer	min: 0, max: 4294967295	No
mesh_group_blocked	Boolean	true, false	No
prefix_attributes_n_flag_clear	Boolean	true, false	No
suppressed	Boolean	true, false	No

address_families (nxos.devices.configuration.routing.isis_instances)

Name	Type	Constraint	Mandatory	Default Value
address_family	Choice	ipv4-unicast, ipv6-unicast	Yes
segment_routing_mpls	Boolean	true, false	No
bfd	Boolean	true, false	No
advertise_passive_only_level_1	Boolean	true, false	No
advertise_passive_only_level_2	Boolean	true, false	No
adjacency_check	Boolean	true, false	No
default_information_originate	Choice	off, on, always	No
default_information_originate_route_map	String		No
distance	Integer	min: 1, max: 255	No
maximum_paths	Integer	min: 1, max: 64	No
multi_topology	Choice	standard, multi-topology, multi-topology-transition	No
router_id_interface_type	Choice	ethernet, loopback, mgmt, port-channel, vlan, vni	No
router_id_interface_id	Any	String or Integer[min: 0]	No
router_id_ip_address	IP		No
table_map	String		No
table_map_filter	Boolean	true, false	No
distributions	List	distributions	No
redistributions	List	redistributions	No
summary_addresses	List	summary_addresses	No

address_families (nxos.devices.configuration.routing.isis_instances)

Name	Type	Constraint	Mandatory	Default Value
address_family	Choice	ipv4-unicast, ipv6-unicast	Yes
segment_routing_mpls	Boolean	true, false	No
bfd	Boolean	true, false	No
advertise_passive_only_level_1	Boolean	true, false	No
advertise_passive_only_level_2	Boolean	true, false	No
adjacency_check	Boolean	true, false	No
default_information_originate	Choice	off, on, always	No
default_information_originate_route_map	String		No
distance	Integer	min: 1, max: 255	No
maximum_paths	Integer	min: 1, max: 64	No
multi_topology	Choice	standard, multi-topology, multi-topology-transition	No
router_id_interface_type	Choice	ethernet, loopback, mgmt, port-channel, vlan, vni	No
router_id_interface_id	Any	String or Integer[min: 0]	No
router_id_ip_address	IP		No
table_map	String		No
table_map_filter	Boolean	true, false	No

vrfs (nxos.devices.configuration.routing.isis_instances)

Name	Type	Constraint	Mandatory	Default Value
vrf	String		Yes
shutdown	Boolean	true, false	No
authentication_check_level_1	Boolean	true, false	No
authentication_check_level_2	Boolean	true, false	No
authentication_key_chain_level_1	String		No
authentication_key_chain_level_2	String		No
authentication_type_level_1	Choice	cleartext, md5, unknown	No
authentication_type_level_2	Choice	cleartext, md5, unknown	No
reference_bandwidth	Integer	min: 0, max: 4294967295	No
reference_bandwidth_unit	Choice	mbps, gbps	No
is_type	Choice	level-1, level-2, level-1-2	No
log_adjacency_changes	Boolean	true, false	No
metric_style	Choice	narrow, wide, transition	No
lsp_mtu	Integer	min: 256, max: 4352	No
net	String		No
passive_interface_default	Choice	level-1, level-2, level-1-2, unknown	No
max_lsp_lifetime	Integer	min: 1, max: 65535	No
queue_limit	Integer	min: 200, max: 65535	No
set_overload_bit	Choice	off, always, on-startup, on-startup-wait-for-bgp, on-startup-wait-for-bgp-max-wait	No
set_overload_bit_on_startup	Integer	min: 5, max: 86400	No
set_overload_bit_wait_for_bgp	Integer	min: 0, max: 65535	No
set_overload_bit_suppress	Choice	interlevel, external	No
spf_interval_level_1_max_wait	Integer	min: 50, max: 120000	No
spf_interval_level_1_initial_wait	Integer	min: 50, max: 120000	No
spf_interval_level_1_second_wait	Integer	min: 50, max: 120000	No
spf_interval_level_2_max_wait	Integer	min: 50, max: 120000	No
spf_interval_level_2_initial_wait	Integer	min: 50, max: 120000	No
spf_interval_level_2_second_wait	Integer	min: 50, max: 120000	No
lsp_gen_interval_level_1_max_wait	Integer	min: 50, max: 120000	No
lsp_gen_interval_level_1_initial_wait	Integer	min: 50, max: 120000	No
lsp_gen_interval_level_1_second_wait	Integer	min: 50, max: 120000	No
lsp_gen_interval_level_2_max_wait	Integer	min: 50, max: 120000	No
lsp_gen_interval_level_2_initial_wait	Integer	min: 50, max: 120000	No
lsp_gen_interval_level_2_second_wait	Integer	min: 50, max: 120000	No
graceful_restart	Boolean	true, false	No
graceful_restart_t3_manual	Integer	min: 30, max: 65535	No
address_families	List	address_families	No

vrfs (nxos.devices.configuration.routing.isis_instances)

Name	Type	Constraint	Mandatory	Default Value
vrf	String		Yes
shutdown	Boolean	true, false	No
authentication_check_level_1	Boolean	true, false	No
authentication_check_level_2	Boolean	true, false	No
authentication_key_chain_level_1	String		No
authentication_key_chain_level_2	String		No
authentication_type_level_1	Choice	cleartext, md5, unknown	No
authentication_type_level_2	Choice	cleartext, md5, unknown	No
reference_bandwidth	Integer	min: 0, max: 4294967295	No
reference_bandwidth_unit	Choice	mbps, gbps	No
is_type	Choice	level-1, level-2, level-1-2	No
log_adjacency_changes	Boolean	true, false	No
metric_style	Choice	narrow, wide, transition	No
lsp_mtu	Integer	min: 256, max: 4352	No
net	String		No
passive_interface_default	Choice	level-1, level-2, level-1-2, unknown	No
max_lsp_lifetime	Integer	min: 1, max: 65535	No
queue_limit	Integer	min: 200, max: 65535	No
set_overload_bit	Choice	off, always, on-startup, on-startup-wait-for-bgp, on-startup-wait-for-bgp-max-wait	No
set_overload_bit_on_startup	Integer	min: 5, max: 86400	No
set_overload_bit_wait_for_bgp	Integer	min: 0, max: 65535	No
set_overload_bit_suppress	Choice	interlevel, external	No
address_families	List	address_families	No

distributions (nxos.devices.configuration.routing.isis_instances.address_families)

Name	Type	Constraint	Mandatory	Default Value
source_level	Choice	level-1, level-2	Yes
destination_level	Choice	level-1, level-2	Yes
route_map	String		No
all	Boolean	true, false	No

redistributions (nxos.devices.configuration.routing.isis_instances.address_families)

Name	Type	Constraint	Mandatory	Default Value
protocol	Choice	static, direct, bgp, isis, ospf, ospfv3, eigrp, rip, amt	Yes
protocol_instance	String		No
asn	Any	String or Integer[min: 0, max: 4294967295]	No
route_map	String		No

summary_addresses (nxos.devices.configuration.routing.isis_instances.address_families)

Name	Type	Constraint	Mandatory	Default Value
prefix	IP		Yes
level	Choice	level-1, level-2, level-1-2	Yes

Examples

Example 1: Basic IS-IS L2-only underlay for spine-leaf fabric

nxos:
  devices:
    - name: LEAF1
      configuration:
        routing:
          isis_instances:
            - name: FABRIC
              is_type: level-2
              net: 49.0001.0101.0010.0003.00
              metric_style: wide
              log_adjacency_changes: true
              address_families:
                - address_family: ipv4-unicast
                  maximum_paths: 4
        interfaces:
          loopbacks:
            - id: 0
              isis:
                instance_name: FABRIC
                passive_interface: level-1-2
            - id: 1
              isis:
                instance_name: FABRIC
                passive_interface: level-1-2
          ethernets:
            - id: 1/1
              isis:
                instance_name: FABRIC
                network_point_to_point: true
            - id: 1/2
              isis:
                instance_name: FABRIC
                network_point_to_point: true

Example 2: IS-IS with BFD, authentication, and tuned timers

nxos:
  devices:
    - name: SPINE1
      configuration:
        routing:
          isis_instances:
            - name: FABRIC
              is_type: level-2
              net: 49.0001.0101.0010.0001.00
              metric_style: wide
              log_adjacency_changes: true
              authentication_type_level_2: md5
              authentication_key_chain_level_2: FABRIC-KEY
              authentication_check_level_2: true
              address_families:
                - address_family: ipv4-unicast
                  bfd: true
                  maximum_paths: 8
        interfaces:
          loopbacks:
            - id: 0
              isis:
                instance_name: FABRIC
                passive_interface: level-1-2
            - id: 100
              isis:
                instance_name: FABRIC
                passive_interface: level-1-2
          ethernets:
            - id: 1/1
              isis:
                instance_name: FABRIC
                network_point_to_point: true
                hello_interval_level_2: 3
                hello_multiplier_level_2: 3
                metric_level_2: 10
            - id: 1/2
              isis:
                instance_name: FABRIC
                network_point_to_point: true
                hello_interval_level_2: 3
                hello_multiplier_level_2: 3
                metric_level_2: 10

Example 3: IS-IS with overload bit and dual address-family for IPv4/IPv6

nxos:
  devices:
    - name: LEAF2
      configuration:
        routing:
          isis_instances:
            - name: FABRIC
              is_type: level-2
              net: 49.0001.0101.0010.0004.00
              metric_style: wide
              set_overload_bit: on-startup
              set_overload_bit_on_startup: 300
              address_families:
                - address_family: ipv4-unicast
                  bfd: true
                  maximum_paths: 4
                - address_family: ipv6-unicast
                  bfd: true
                  maximum_paths: 4
        interfaces:
          loopbacks:
            - id: 0
              isis:
                instance_name: FABRIC
                ipv4: true
                ipv6: true
                passive_interface: level-1-2
          ethernets:
            - id: 1/1
              isis:
                instance_name: FABRIC
                ipv4: true
                ipv6: true
                network_point_to_point: true
                metric_level_2: 100

Example 4: IS-IS L1/L2 with SPF and LSP generation tuning, graceful restart, redistribution, route leaking, and summarization

nxos:
  devices:
    - name: BORDER1
      configuration:
        routing:
          isis_instances:
            - name: FABRIC
              is_type: level-1-2
              net: 49.0001.0101.0010.0005.00
              metric_style: wide
              spf_interval_level_2_max_wait: 5000
              spf_interval_level_2_initial_wait: 50
              spf_interval_level_2_second_wait: 100
              lsp_gen_interval_level_2_max_wait: 5000
              lsp_gen_interval_level_2_initial_wait: 50
              lsp_gen_interval_level_2_second_wait: 100
              graceful_restart: true
              graceful_restart_t3_manual: 120
              address_families:
                - address_family: ipv4-unicast
                  redistributions:
                    - protocol: direct
                      route_map: DIRECT_TO_ISIS
                    - protocol: bgp
                      asn: "65000"
                      route_map: BGP_TO_ISIS
                  distributions:
                    - source_level: level-2
                      destination_level: level-1
                      route_map: L2_TO_L1
                  summary_addresses:
                    - prefix: 10.0.0.0/8
                      level: level-2

Examples

Example 1: Basic IS-IS L2-only underlay for spine-leaf fabric

nxos:
  devices:
    - name: LEAF1
      configuration:
        routing:
          isis_instances:
            - name: FABRIC
              is_type: level-2
              net: 49.0001.0101.0010.0003.00
              metric_style: wide
              log_adjacency_changes: true
              address_families:
                - address_family: ipv4-unicast
                  maximum_paths: 4
        interfaces:
          loopbacks:
            - id: 0
              isis:
                instance_name: FABRIC
                passive_interface: l12
            - id: 1
              isis:
                instance_name: FABRIC
                passive_interface: level-1-2
          ethernets:
            - id: 1/1
              isis:
                instance_name: FABRIC
                network_point_to_point: true
            - id: 1/2
              isis:
                instance_name: FABRIC
                network_point_to_point: true

Example 2: IS-IS with BFD, authentication, and tuned timers

nxos:
  devices:
    - name: SPINE1
      configuration:
        routing:
          isis_instances:
            - name: FABRIC
              is_type: level-2
              net: 49.0001.0101.0010.0001.00
              metric_style: wide
              log_adjacency_changes: true
              authentication_type_level_2: md5
              authentication_key_chain_level_2: FABRIC-KEY
              authentication_check_level_2: true
              address_families:
                - address_family: ipv4-unicast
                  bfd: true
                  maximum_paths: 8
        interfaces:
          loopbacks:
            - id: 0
              isis:
                instance_name: FABRIC
                passive_interface: l12
            - id: 100
              isis:
                instance_name: FABRIC
                passive_interface: l12
          ethernets:
            - id: 1/1
              isis:
                instance_name: FABRIC
                network_point_to_point: "on"
                hello_interval_level_2: 3
                hello_multiplier_level_2: 3
                metric_level_2: 10
            - id: 1/2
              isis:
                instance_name: FABRIC
                network_point_to_point: "on"
                hello_interval_level_2: 3
                hello_multiplier_level_2: 3
                metric_level_2: 10

Example 3: IS-IS with overload bit and dual address-family for IPv4/IPv6

nxos:
  devices:
    - name: LEAF2
      configuration:
        routing:
          isis_instances:
            - name: FABRIC
              is_type: level-2
              net: 49.0001.0101.0010.0004.00
              metric_style: wide
              set_overload_bit: on-startup
              set_overload_bit_on_startup: 300
              address_families:
                - address_family: ipv4-unicast
                  bfd: true
                  maximum_paths: 4
                - address_family: ipv6-unicast
                  bfd: true
                  maximum_paths: 4
        interfaces:
          loopbacks:
            - id: 0
              isis:
                instance_name: FABRIC
                ipv4: true
                ipv6: true
                passive_interface: l12
          ethernets:
            - id: 1/1
              isis:
                instance_name: FABRIC
                ipv4: true
                ipv6: true
                network_point_to_point: "on"
                metric_level_2: 100