Prefix List

Configure IPv4 and IPv6 prefix lists for route filtering and access control. Prefix lists provide a powerful mechanism to filter routes based on network prefixes and prefix lengths, commonly used in routing policies, route maps, and access control.

Diagram

Classes

configuration (iosxr.devices)

Name	Type	Constraint	Mandatory	Default Value
prefix_lists	Class	`[prefix_lists]`	No

prefix_lists (iosxr.devices.configuration)

Name	Type	Constraint	Mandatory	Default Value
ipv4	List	`[ipv4]`	No
ipv6	List	`[ipv6]`	No

ipv4 (iosxr.devices.configuration.prefix_lists)

Name	Type	Constraint	Mandatory	Default Value
name	String	max: `32`	Yes
entries	List	`[entries]`	No

ipv6 (iosxr.devices.configuration.prefix_lists)

Name	Type	Constraint	Mandatory	Default Value
name	String	max: `32`	Yes
entries	List	`[entries]`	No

entries (iosxr.devices.configuration.prefix_lists.ipv4)

Name	Type	Constraint	Mandatory
sequence	Integer	min: `1`, max: `2147483646`	Yes
action	Choice	`deny`, `permit`	No
exact_length	Integer	min: `0`, max: `32`	No
mask	Any	String or Integer[min: `0`, max: `32`] or String[Regex: `^.[\$\%]\{.$`]	No
max_length	Integer	min: `0`, max: `32`	No
min_length	Integer	min: `0`, max: `32`	No
prefix	IP		No
remark	String		No

entries (iosxr.devices.configuration.prefix_lists.ipv6)

Name	Type	Constraint	Mandatory
sequence	Integer	min: `1`, max: `2147483646`	Yes
action	Choice	`deny`, `permit`	No
exact_length	Integer	min: `0`, max: `128`	No
mask	Integer	min: `0`, max: `128`	No
max_length	Integer	min: `0`, max: `128`	No
min_length	Integer	min: `0`, max: `128`	No
prefix	IP		No
remark	String		No
zone	Integer	min: `0`, max: `4294967295`	No

Guidelines and Limitations

IPv6 prefix list remarks (remark) are not supported via gNMI. Use remarks only in IPv4 prefix lists.

Data Normalization

IPv4 Mask Formats

The IPv4 mask field accepts both dotted-decimal and prefix-length:

dotted-decimal (e.g., 255.255.255.0)
prefix-length integer (e.g., 24)

Both formats can be used interchangeably. The normalization layer automatically converts prefix-length integers to dotted-decimal before sending to the device, preventing configuration drift.

Example YAML Code:

Example-1: IPv4 prefix list with permit and deny entries.

iosxr:
  devices:
    - name: router-1
      host: 10.10.10.1:57400
      configuration:
        prefix_lists:
          ipv4:
            - name: MGMT_NETWORKS
              entries:
                - sequence: 10
                  action: permit
                  prefix: 192.168.1.0
                  mask: 255.255.255.0
                  exact_length: 24
                - sequence: 20
                  action: deny
                  prefix: 0.0.0.0
                  mask: 0.0.0.0

Example-2: IPv4 prefix list with remarks and range matching.

iosxr:
  devices:
    - name: router-1
      host: 10.10.10.1:57400
      configuration:
        prefix_lists:
          ipv4:
            - name: MGMT_NETWORKS
              entries:
                - sequence: 5
                  remark: "Allow management subnet"
                - sequence: 10
                  action: permit
                  prefix: 192.168.1.0
                  mask: 24
                  exact_length: 24
                - sequence: 20
                  action: permit
                  prefix: 10.0.0.0
                  mask: 255.0.0.0
                  min_length: 8
                  max_length: 24
                - sequence: 25
                  remark: "Deny all others"
                - sequence: 30
                  action: deny
                  prefix: 0.0.0.0
                  mask: 0.0.0.0

Example-3: IPv6 prefix list with permit/deny entries and zone.

iosxr:
  devices:
    - name: router-1
      host: 10.10.10.1:57400
      configuration:
        prefix_lists:
          ipv6:
            - name: IPV6_MGMT
              entries:
                - sequence: 10
                  action: permit
                  prefix: "2001:db8:1::"
                  mask: 48
                  min_length: 64
                  max_length: 128
                - sequence: 20
                  action: deny
                  prefix: "::"
                  mask: 0

Example-4: IPv4 and IPv6 prefix lists on one device.

iosxr:
  devices:
    - name: router-1
      host: 10.10.10.1:57400
      configuration:
        prefix_lists:
          ipv4:
            - name: MGMT_NETWORKS
              entries:
                - sequence: 10
                  action: permit
                  prefix: 192.168.1.0
                  mask: 255.255.255.0
                  exact_length: 24
            - name: LOOPBACK_NETWORKS
              entries:
                - sequence: 10
                  action: permit
                  prefix: 172.16.0.0
                  mask: 255.240.0.0
                  exact_length: 32
          ipv6:
            - name: IPV6_MGMT
              entries:
                - sequence: 10
                  action: permit
                  prefix: "2001:db8:1::"
                  mask: 48
                  min_length: 64
                  max_length: 128
            - name: IPV6_LOOPBACKS
              entries:
                - sequence: 10
                  action: permit
                  prefix: "2001:db8:ffff::"
                  mask: 48
                  exact_length: 128