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.

Diagram

Classes

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

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
isis	Class	`[isis]`	No

isis_instances (nxos.devices.configuration.routing)

Name	Type	Constraint	Mandatory
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_instances (nxos.devices.configuration.routing)

Name	Type	Constraint	Mandatory
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	`clear`, `md5`, `unknown`	No
authentication_type_level_2	Choice	`clear`, `md5`, `unknown`	No
bandwidth_reference	Integer	min: `0`, max: `4294967295`	No
bandwidth_reference_unit	Choice	`mbps`, `gbps`	No
is_type	Choice	`l1`, `l2`, `l12`	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_default	Choice	`l1`, `l2`, `l12`, `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`, `bootup`, `bgp-converge`, `bgp-converge-max-wait`	No
overload_startup_time	Integer	min: `5`, max: `86400`	No
overload_bgp_as_number	Integer	min: `0`, max: `65535`	No
overload_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
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

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

Name	Type	Constraint	Mandatory
instance_name	String		Yes
circuit_type	Choice	`l1`, `l2`, `l12`	No
ipv4	Boolean	`true`, `false`	No
ipv6	Boolean	`true`, `false`	No
network_point_to_point	Choice	`off`, `on`, `use-all-is-mac`	No
passive_interface	Choice	`l1`, `l2`, `l12`, `no-l1`, `no-l2`, `no-l12`, `inherit-def`	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
n_flag_clear	Boolean	`true`, `false`	No
suppress_prefix	Boolean	`true`, `false`	No

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

Name	Type	Constraint	Mandatory
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

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

Name	Type	Constraint	Mandatory
address_family	Choice	`ipv4-unicast`, `ipv6-unicast`	Yes
segment_routing_mpls	Boolean	`true`, `false`	No
bfd	Boolean	`true`, `false`	No
advertise_passive_only_l1	Boolean	`true`, `false`	No
advertise_passive_only_l2	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	String		No
router_id_ip_address	String		No
table_map	String		No
table_map_filter	Boolean	`true`, `false`	No

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

Name	Type	Constraint	Mandatory
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

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

Name	Type	Constraint	Mandatory
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	`clear`, `md5`, `unknown`	No
authentication_type_level_2	Choice	`clear`, `md5`, `unknown`	No
bandwidth_reference	Integer	min: `0`, max: `4294967295`	No
bandwidth_reference_unit	Choice	`mbps`, `gbps`	No
is_type	Choice	`l1`, `l2`, `l12`	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_default	Choice	`l1`, `l2`, `l12`, `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`, `bootup`, `bgp-converge`, `bgp-converge-max-wait`	No
overload_startup_time	Integer	min: `5`, max: `86400`	No
overload_bgp_as_number	Integer	min: `0`, max: `65535`	No
overload_suppress	Choice	`interlevel`, `external`	No
address_families	List	`[address_families]`	No

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

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: l2
              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: l12
          ethernets:
            - id: 1/1
              isis:
                instance_name: FABRIC
                network_point_to_point: "on"
            - id: 1/2
              isis:
                instance_name: FABRIC
                network_point_to_point: "on"

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

nxos:
  devices:
    - name: SPINE1
      configuration:
        routing:
          isis_instances:
            - name: FABRIC
              is_type: l2
              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: l2
              net: 49.0001.0101.0010.0004.00
              metric_style: wide
              set_overload_bit: bootup
              overload_startup_time: 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