Access List

Access lists are security and traffic control mechanisms that filter network traffic based on various criteria including source and destination IP addresses, ports, protocols, and other packet characteristics. They serve as fundamental building blocks for implementing security policies, Quality of Service (QoS), and network access control by permitting or denying traffic that matches specific conditions. Access lists can be applied to interfaces, routing protocols, and various network services to enforce granular traffic filtering and policy enforcement throughout the network infrastructure.

Diagram

Classes

configuration (iosxe.devices)

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

access_lists (iosxe.devices.configuration)

Name	Type	Constraint	Mandatory
standard	List	`[standard]`	No
extended	List	`[extended]`	No
role_based	List	`[role_based]`	No
as_path	List	`[as_path]`	No

standard (iosxe.devices.configuration.access_lists)

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

extended (iosxe.devices.configuration.access_lists)

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

role_based (iosxe.devices.configuration.access_lists)

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

as_path (iosxe.devices.configuration.access_lists)

Name	Type	Constraint	Mandatory	Default Value
number	Integer	min: `1`, max: `500`	Yes
entries	List	`[entries]`	No

entries (iosxe.devices.configuration.access_lists.standard)

Name	Type	Constraint	Mandatory
sequence	Integer		Yes
remark	String		No
action	Choice	`deny`, `permit`	No
prefix	IP		No
prefix_mask	IP		No
any	Boolean	`true`, `false`	No
host	IP		No
log	Boolean	`true`, `false`	No

entries (iosxe.devices.configuration.access_lists.extended)

Name	Type	Constraint	Mandatory
sequence	Integer		Yes
remark	String		No
action	Choice	`deny`, `permit`	No
protocol	Any	Choice[`ahp`, `eigrp`, `esp`, `gre`, `icmp`, `igmp`, `ip`, `ipinip`, `nos`, `object-group`, `ospf`, `pcp`, `pim`, `tcp`, `udp`] or Integer[min: `0`, max: `255`] or String[Regex: `^.[\$\%]\{.$`]	No
service_object_group	String		No
source	Class	`[source]`	No
destination	Class	`[destination]`	No
tcp_flags	Any	List[Choice[`ack`, `fin`, `psh`, `rst`, `syn`, `urg`]]	No
established	Boolean	`true`, `false`	No
fragments	Boolean	`true`, `false`	No
dscp	Any	Choice[`af11`, `af12`, `af13`, `af21`, `af22`, `af23`, `af31`, `af32`, `af33`, `af41`, `af42`, `af43`, `cs1`, `cs2`, `cs3`, `cs4`, `cs5`, `cs6`, `cs7`, `default`, `dscp`, `ef`, `precedence`] or Integer[min: `0`, max: `63`] or String[Regex: `^.[\$\%]\{.$`]	No
precedence	Any	Choice[`critical`, `flash`, `flash-override`, `immediate`, `internet`, `network`, `priority`, `routine`] or Integer[min: `0`, max: `7`] or String[Regex: `^.[\$\%]\{.$`]	No
tos	Any	Choice[`max-reliability`, `max-throughput`, `min-delay`, `min-monetary-cost`, `normal`] or Integer[min: `0`, max: `15`] or String[Regex: `^.[\$\%]\{.$`]	No
icmp_message_type	Any	String or Integer[min: `0`, max: `255`] or String[Regex: `^.[\$\%]\{.$`]	No
icmp_message_code	Integer	min: `0`, max: `255`	No
log	Boolean	`true`, `false`	No
log_input	Boolean	`true`, `false`	No

entries (iosxe.devices.configuration.access_lists.role_based)

Name	Type	Constraint	Mandatory
sequence	Integer	min: `1`, max: `2147483647`	Yes
remark	String		No
action	Choice	`deny`, `permit`	No
protocol	Any	Choice[`ahp`, `eigrp`, `esp`, `gre`, `icmp`, `igmp`, `ip`, `ipinip`, `nos`, `object-group`, `ospf`, `pcp`, `pim`, `tcp`, `udp`] or Integer[min: `0`, max: `255`] or String[Regex: `^.[\$\%]\{.$`]	No
tcp_flags	Any	List[Choice[`ack`, `fin`, `psh`, `rst`, `syn`, `urg`]]	No
established	Boolean	`true`, `false`	No
fragments	Boolean	`true`, `false`	No
dscp	Any	Choice[`af11`, `af12`, `af13`, `af21`, `af22`, `af23`, `af31`, `af32`, `af33`, `af41`, `af42`, `af43`, `cs1`, `cs2`, `cs3`, `cs4`, `cs5`, `cs6`, `cs7`, `default`, `dscp`, `ef`, `precedence`] or Integer[min: `0`, max: `63`] or String[Regex: `^.[\$\%]\{.$`]	No
precedence	Any	Choice[`critical`, `flash`, `flash-override`, `immediate`, `internet`, `network`, `priority`, `routine`] or Integer[min: `0`, max: `7`] or String[Regex: `^.[\$\%]\{.$`]	No
tos	Any	Choice[`max-reliability`, `max-throughput`, `min-delay`, `min-monetary-cost`, `normal`] or Integer[min: `0`, max: `15`] or String[Regex: `^.[\$\%]\{.$`]	No
option	Any	Choice[`add-ext`, `any-options`, `com-security`, `dps`, `encode`, `eool`, `ext-ip`, `ext-security`, `finn`, `imitd`, `lsr`, `mtup`, `mtur`, `no-op`, `nsapa`, `record-route`, `router-alert`, `sdb`, `security`, `ssr`, `stream-id`, `timestamp`, `traceroute`, `ump`, `visa`, `zsu`] or Integer[min: `0`, max: `255`] or String[Regex: `^.[\$\%]\{.$`]	No
time_range	String		No
log	Boolean	`true`, `false`	No
log_input	Boolean	`true`, `false`	No
match_all	List	Choice[`+ack`, `+fin`, `+psh`, `+rst`, `+syn`, `+urg`, `-ack`, `-fin`, `-psh`, `-rst`, `-syn`, `-urg`]	No
match_any	List	Choice[`+ack`, `+fin`, `+psh`, `+rst`, `+syn`, `+urg`, `-ack`, `-fin`, `-psh`, `-rst`, `-syn`, `-urg`]	No

entries (iosxe.devices.configuration.access_lists.as_path)

Name	Type	Constraint	Mandatory	Default Value
action	Choice	`permit`, `deny`	Yes
regex	String		Yes

source (iosxe.devices.configuration.access_lists.extended.entries)

Name	Type	Constraint	Mandatory
prefix	IP		No
prefix_mask	IP		No
any	Boolean	`true`, `false`	No
host	IP		No
object_group	String		No
port_type	Choice	`equal`, `greater_than`, `lesser_than`, `range`	No
port	Any	Integer or String[Regex: `^.[\$\%]\{.$`] or String	No
port_range_from	Integer		No
port_range_to	Integer		No

destination (iosxe.devices.configuration.access_lists.extended.entries)

Name	Type	Constraint	Mandatory
prefix	IP		No
prefix_mask	IP		No
any	Boolean	`true`, `false`	No
host	IP		No
object_group	String		No
port_type	Choice	`equal`, `greater_than`, `lesser_than`, `range`	No
port	Any	Integer or String[Regex: `^.[\$\%]\{.$`] or String	No
additional_equal_ports	List	Integer	No
port_range_from	Integer		No
port_range_to	Integer		No

By defining granular rules for traffic filtering, Access Lists enhance network security, control resource access, and ensure efficient network operation. They are crucial for implementing security policies at the network edge and within internal segments.

Access List Parameters:

ACL Name (Standard/Extended)
Entry Sequence Number
Action (Permit/Deny)
Source IP Address/Network
Source Wildcard Mask
Destination IP Address/Network (Extended ACLs)
Destination Wildcard Mask (Extended ACLs)
Protocol (Extended ACLs)
Port Numbers (Extended ACLs)

You can use these Access List parameters to define precise traffic filtering rules for your network devices. Customize the type, entries, and matching criteria to fit your network’s security and operational needs. Adjusting these parameters lets you tailor access control for your environment.

Guidelines and Limitations

Port Attribute Dependencies:

When defining port-specific attributes on extended ACL entries, the port_type attribute must be explicitly defined with an appropriate value:
- If using port_range_from or port_range_to, port_type must be set to range
- If using port, port_type must be set to one of: equal, greater_than, or lesser_than
- If using additional_equal_ports (destination only), port_type must be set to equal
This requirement applies to both source and destination port configurations
Failure to define port_type when using port attributes will result in validation errors

Sample Configuration:

The following configuration describes how to set up Standard and Extended IP Access Lists on an IOS-XE device. It lists how to define rules for permitting and denying traffic based on various criteria, including port-based filtering.

ip access-list standard StandardAccessList1
 10 permit 10.0.0.0 0.0.0.255
 20 permit 20.0.0.0 0.0.0.255
!
ip access-list extended ExtendedAccessList1
 10 permit ip any any
 20 deny tcp any any syn ack
 30 deny tcp any any eq 80
 40 permit tcp any range 8000 8080 any
 50 deny tcp any any gt 1024
 60 permit tcp any any eq 443 www 8443

Example Code:

iosxe:
  devices:
    - name: Device1
      configuration:
        access_lists:
          standard:
            - name: StandardAccessList1
              entries:
                - sequence: 10
                  action: permit
                  prefix: 10.0.0.0
                  prefix_mask: 0.0.0.255
                - sequence: 20
                  action: permit
                  prefix: 20.0.0.0
                  prefix_mask: 0.0.0.255
          extended:
            - name: ExtendedAccessList1
              entries:
                # Basic permit all IP traffic
                - sequence: 10
                  action: permit
                  protocol: ip
                  source:
                    any: true
                  destination:
                    any: true
                # Deny TCP traffic with SYN and ACK flags set
                - sequence: 20
                  action: deny
                  protocol: tcp
                  tcp_flags: [syn, ack]
                  source:
                    any: true
                  destination:
                    any: true
                # Deny HTTP traffic (port 80) - demonstrates 'equal' port_type
                - sequence: 30
                  action: deny
                  protocol: tcp
                  source:
                    any: true
                  destination:
                    any: true
                    port_type: equal
                    port: 80
                # Permit traffic from ports 8000-8080 - demonstrates 'range' port_type
                - sequence: 40
                  action: permit
                  protocol: tcp
                  source:
                    any: true
                    port_type: range
                    port_range_from: 8000
                    port_range_to: 8080
                  destination:
                    any: true
                # Deny traffic to ports greater than 1024 - demonstrates 'greater_than' port_type
                - sequence: 50
                  action: deny
                  protocol: tcp
                  source:
                    any: true
                  destination:
                    any: true
                    port_type: greater_than
                    port: 1024
                # Permit HTTPS and HTTP traffic - demonstrates multiple equal ports
                - sequence: 60
                  action: permit
                  protocol: tcp
                  source:
                    any: true
                  destination:
                    any: true
                    port_type: equal
                    port: 443
                    additional_equal_ports: [80, 8443]