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The ability to filter packets in a modular and scalable way is important for both network security and network management. Access Control Lists (ACLs) provide the capability to filter packets at a fine granularity. In Metro Ethernet networks, ACLs are directly applied on Ethernet virtual circuits (EVCs).
Layer 2 Access Control Lists on EVCs is a security feature that allows packet filtering based on MAC addresses. This module describes how to implement ACLs on EVCs.
Knowledge of how service instances must be configured.
Knowledge of extended MAC ACLs and how they must be configured.
You can enable a packet capture on the host, based on Layer 2 packet header per EFP (for example, dst-mac , src-mac and CoS field). Create a pcap of the captured packet on host machine.
A maximum of 16512 access control entries (ACEs) are allowed for a given ACL, with the limitation that it does not exceed the maximum tcam entries.
Only 256 different or unique Layer 2 ACLs can be configured on a line card. (More than 256 ACLs can be configured on a router and it depends on the number of TCAM that is free for programming these ACLs.)
L2 ACL is supported over port channel with Normal EFPs.
Egress L2 ACL on EVC is not supported.
L2 ACLs are not supported on Trunk EFP.
L2 ACL counters are not supported.
Layer2 ACL can be applied on layer 2 frame without IPv4 or IPv6 header as layer 2 ACL does not support filter on IPv4 or IPv6 traffic.
Layer 2 ACLs function inbound only. The Layer 2 ACLs are not supported at physical interface level.
Current Layer 2 ACLs provide Layer 3 filtering options in permit and deny rules. Options that are not relevant to service instances are ignored.
An Ethernet virtual circuit (EVC) as defined by the Metro Ethernet Forum is a port-level point-to-point or multipoint-to-multipoint Layer 2 circuit. It is an end-to-end representation of a single instance of a Layer 2 service being offered by a provider to a customer. An EVC contains the different parameters on which the service is being offered. A service instance is the instantiation of an EVC on a specified port.
Service instances are configured under a port channel. The traffic carried by the service instance is load balanced across member links. Service instances under a port channel are grouped and each group is associated with one member link. Ingress traffic for a single EVC can arrive on any member of the bundle. All egress traffic for a service instance uses only one of the member links. Load balancing is achieved by grouping service instances and assigning them to a member link.
Ethernet virtual connection services (EVCS) uses the EVCs and service instances to provide Layer 2 switched Ethernet services. EVC status can be used by a customer edge (CE) device either to find an alternative path to the service provider network or in some cases, to fall back to a backup path over Ethernet or over another alternative service such as ATM.
For information about the Metro Ethernet Forum standards, see the Standards table in the “Additional References” section.
The following points capture the relationship between ACLs and Ethernet Infrastructure (EI):
ACLs can be directly applied on an EVC using the command-line interface (CLI). An ACL is applied to a service instance, which is the instantiation of an EVC on a given port.
One ACL can be applied to more than one service instance at any time.
One service instance can have one ACL at most applied to it at any time. If a Layer 2 ACL is applied to a service instance that already has a Layer 2 ACL, the new one replaces the old one.
Only named ACLs can be applied to service instances. The command syntax ACLs is retained; the mac access-list extended command is used to create an ACL.
The show ethernet service instance id id interface type number detail show ethernet service instance command can be used to provide details about ACLs on service instances.
Perform this task to create a Layer 2 ACL with a single ACE.
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Step 1 |
enable Example:Enables privileged EXEC mode.
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Step 2 |
configure terminal Example:Enters global configuration mode. |
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Step 3 |
mac access-list extended name Example:Defines an extended MAC ACL and enters mac access list control configuration mode. |
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Step 4 |
permit {{src-mac mask | any } {dest-mac mask | any } [protocol [vlan vlan ] [cos value ]]} Example:Allows forwarding of Layer 2 traffic if the conditions are matched. Creates an ACE for the ACL. |
Perform this task to apply a Layer 2 ACL to a service instance. Note that packet filtering takes place only after the ACL has been created and applied to the service instance.
Before applying an ACL to a service instance, you must create it using the mac access-list extended command. See the “Creating a Layer 2 ACL” section.
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Step 1 |
enable Example:Enables privileged EXEC mode.
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Step 2 |
configure terminal Example:Enters global configuration mode. |
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Step 3 |
interface type number Example:Specifies the type and location of the interface to configure, where:
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Step 4 |
service instance id ethernet Example:Configures an Ethernet service instance on an interface and enters Ethernet service configuration mode. |
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Step 5 |
encapsulation dot1q vlan-id Example:Defines the matching criteria to be used in order to map ingress dot1q frames on an interface to the appropriate service instance. |
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Step 6 |
mac access-group access-list-name in Example:Applies a MAC ACL to control incoming traffic on the interface. |
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Step 7 |
bridge -domain bridge-id in Example:Configure the bridge domain ID. |
Perform this task to configure the same ACL with three ACEs and stop all other traffic on a service instance.
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Step 1 |
enable Example:Enables privileged EXEC mode.
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Step 2 |
configure terminal Example:Enters global configuration mode. |
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Step 3 |
mac access-list extended name Example:Defines an extended MAC ACL and enters mac access control list configuration mode. |
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Step 4 |
permit {src-mac mask | any } {dest-mac mask | any } Example:Allows forwarding of Layer 2 traffic if the conditions are matched. This creates an ACE for the ACL. |
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Step 5 |
permit {src-mac mask | any } {dest-mac mask | any } Example:Allows forwarding of Layer 2 traffic if the conditions are matched. This creates an ACE for the ACL. |
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Step 6 |
permit {src-mac mask | any } {dest-mac mask } | any } Example:Allows forwarding of Layer 2 traffic if the conditions are matched. This creates an ACE for the ACL. |
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Step 7 |
deny any any Example:Prevents forwarding of Layer 2 traffic except for the allowed ACEs. |
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Step 8 |
exit Example:Exits the current command mode and returns to global configuration mode. |
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Step 9 |
interface type number Example:Specifies the interface. |
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Step 10 |
service instance id ethernet Example:Configures an Ethernet service instance on an interface and enters service instance configuration mode. |
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Step 11 |
encapsulation dot1q vlan-id Example:Defines the matching criteria to be used to map ingress dot1q frames on an interface to the appropriate service instance. |
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Step 12 |
mac access-group access-list-name in Example:Applies a MAC ACL to control incoming traffic on the interface. |
Perform this task to verify that a Layer 2 ACL is present on an EVC. This verification task can be used after an ACL has been configured to confirm its presence.
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Step 1 |
enable Example:Enables privileged EXEC mode.
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Step 2 |
configure terminal Example:Enters global configuration mode. |
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Step 3 |
show ethernet service instance id id interface type number detail Example:Displays detailed information about Ethernet customer service instances. |
The following example shows how to apply a Layer 2 ACL called mac-20-acl to a service instance. The ACL has five permitted ACEs and all other traffic is not allowed.
enable
configure terminal
mac access-list extended mac-20-acl
permit 00aa.bbcc.adec 0.0.0 any
permit 00aa.bbcc.bdec 0.0.0 any
permit 00aa.bbcc.cdec 0.0.0 any
permit 00aa.bbcc.edec 0.0.0 any
permit 00aa.bbcc.fdec 0.0.0 any
deny any any
exit
interface gigabitethernet 10/0/0
service instance 100 ethernet
encapsulation dot1q 100
mac access-group mac-20-acl inThe following example shows how to apply a Layer 2 ACL called mac-07-acl to three service instances on the same interface:
enable
configure terminal
mac access-list extended mac-07-acl
permit 00aa.bbcc.adec 0.0.0 any
permit 00aa.bbcc.bdec 0.0.0 any
permit 00aa.bbcc.cdec 0.0.0 any
deny any any
exit
interface gigabitethernet 10/0/0
service instance 100 ethernet
encapsulation dot1q 100
mac access-group mac-07-acl in
service instance 101 ethernet
encapsulation dot1q 101
mac access-group mac-07-acl in
service instance 102 ethernet
encapsulation dot1q 102
mac access-group mac-07-acl inThe following example shows how to create a Layer 2 ACL called mac-11-acl with two permitted ACEs:
enable
configure terminal
mac access-list extended mac-11-acl
permit 00aa.00bb.00cc 1a11.0101.11c1 any
permit 00aa.00bb.00cc 1a11.0101.11c2 anyThe following sample output displays the details of a Layer 2 ACL called test-acl on a service instance.
Device# show ethernet service instance id 100 interface ethernet0/0 detail
Service Instance ID: 100
L2 ACL (inbound): test-acl
Associated Interface: Ethernet0/0
Associated EVC: test
L2protocol drop
CEVlans:
Interface Dot1q Tunnel Ethertype: 0x8100
State: Up
L2 ACL permit count: 10255
L2 ACL deny count: 53
Device# show ethernet service instance id 100 interface gig3/0/1 detail
Service Instance ID: 100
L2 ACL (inbound): test-acl
Associated Interface: Gig3/0/1
Associated EVC: test
L2protocol drop
CEVlans:
Interface Dot1q Tunnel Ethertype: 0x8100
State: Up
L2 ACL permit count: 10255
L2 ACL deny count: 53
The table below describes the significant fields in the output.
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Field |
Description |
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Service Instance ID |
Displays the service instance ID. |
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L2 ACL (inbound): |
Displays the ACL name. |
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Associated Interface: |
Displays the interface details of the service instance. |
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Associated EVC: |
Displays the EVC with which the service instance is associated. |
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CEVlans: |
Displays details of the associated VLAN ID. |
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State: |
Displays whether the service instance is in an up or down state. |
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L2 ACL permit count: |
Displays the number of packet frames allowed to pass on the service instance by the ACL. |
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L2 ACL deny count |
Displays the number of packet frames not permitted to pass on the service instance by the ACL. |
| Related Topic | Document Title |
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Cisco IOS commands |
| Standard/RFC | Title |
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MEF 6.1 |
Metro Ethernet Services Definitions Phase 2 (PDF 6/08) |
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MEF 10.1 |
Ethernet Services Attributes Phase 2 (PDF 10/06) |
| MIB | MIBs Link |
|---|---|
| — |
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL: |
| Description | Link |
|---|---|
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