Cisco 7600 Series Router Software Configuration Guide, Cisco IOS Release 15S

VACL Overview

VACLs can provide access control for all packet s that are bridged within a VLAN or that are routed into or out of a VLAN or a WAN interface for VACL capture. Unlike regular Cisco IOS standard or extended ACLs that are configured on router interfaces only and are applied on routed packets only, VACLs apply to all packets and can be applied to any VLAN or WAN interface. VACLS are processed in hardware. VACLs use Cisco IOS ACLs. VACLs ignore any Cisco IOS ACL fields that are not supported in hardware.

You can configure VACLs for IP, IPX, and MAC-Layer traffic. VACLs applied to WAN interfaces support only IP traffic for VACL capture.

When you configure a VACL and apply it to a VLAN, all packets entering the VLAN are checked against this VACL. If you apply a VACL to the VLAN and an ACL to a routed interface in the VLAN, a packet coming in to the VLAN is first checked against the VACL and, if permitted, is then checked against the input ACL before it is handled by the routed interface. When the packet is routed to another VLAN, it is first checked against the output ACL applied to the routed interface and, if permitted, the VACL configured for the destination VLAN is applied. If a VACL is configured for a packet type and a packet of that type does not match the VACL, the default action is deny.

Note ● TCP Intercepts and Reflexive ACLs take precedence over a VACL action if these are configured on the same interface.

• VACLs and CBAC cannot be configured on the same interface.
• IGMP packets are not checked against VACLs.

Bridged Packets

Figure 38-1 shows a VACL applied on bridged packets.

Figure 38-1 Applying VACLs on Bridged Packets

Routed Packets

Figure 38-2 shows how ACLs are applied on routed and Layer 3-switched packets. For routed or Layer 3-switched packets, the ACLs are applied in the following order:

1. VACL for input VLAN

2. Input Cisco IOS ACL

3. Output Cisco IOS ACL

4. VACL for output VLAN

Figure 38-2 Applying VACLs on Routed Packets

Multicast Packets

Figure 38-3 shows how ACLs are applied on packets that need multicast expansion. For packets that need multicast expansion, the ACLs are applied in the following order:

1. Packets that need multicast expansion:

a. VACL for input VLAN

b. Input Cisco IOS ACL

2. Packets after multicast expansion:

a. Output Cisco IOS ACL

b. VACL for output VLAN

3. Packets originating from router—VACL for output VLAN

Figure 38-3 Applying VACLs on Multicast Packets

VACL Configuration Overview

VACLs use standard and extended Cisco IOS IP and IPX ACLs, and MAC Layer-named ACLs (see the “Configuring MAC ACLs” section) and VLAN access maps.

VLAN access maps can be app

ed to VLANs or to WAN interfaces for VACL capture. VACLs attached to WAN interfaces support only standard and extended Cisco IOS IP ACLs.

Each VLAN access map can consist of one or more map sequences, each sequence with a match clause and an action clause. The match clause specifies IP, IPX, IPv6 or MAC ACLs for traffic filtering and the action clause specifies the action to be taken when a match occurs. When a flow matches a permit ACL entry, the associated action is taken and the flow is not checked against the remaining sequences. When a flow matches a deny ACL entry, it will be checked against the next ACL in the same sequence or the next sequence. If a flow does not match any ACL entry and at least one ACL is configured for that packet type, the packet is denied.

To use access control for both bridged and routed traffic, you can use VACLs alone or a combination of VACLs and ACLs. You can define ACLs on the VLAN interfaces to use access control for both the input and output routed traffic. You can define a VACL to use access control for the bridged traffic.

The following caveats apply to ACLs when used with VACLs:

• Packets that require logging on the outbound ACLs are not logged if they are denied by a VACL.
• VACLs are applied on packets before NAT translation. If the translated flow is not subject to access control, the flow might be subject to access control after the translation because of the VACL configuration.

The action clause in a VACL can be forward, drop, capture, or redirect. Traffic can also be logged. VACLs applied to WAN interfaces do not support the redirect or log actions.

Note ● VACLs have an implicit deny at the end of the map; a packet is denied if it does not match any ACL entry, and at least one ACL is configured for the packet type.

• If an empty or undefined ACL is specified in a VACL, any packets will match the ACL and the associated action is taken.

Note ● All the IP address related restrictions such as address compression that apply to RACL and PACL also apply to VACL.

• While configuring the VACL, the LOG attribute from the ACE is always ignored.

Defining a VLAN Access Map

To define a VLAN access map, perform this task:

When defining a VLAN access map, note the following information:

• To insert or modify an entry, specify the map sequence number.
• If you do not specify the map sequence number, a number is automatically assigned.
• You can specify only one match clause and one action clause per map sequence.
• Use the no keyword with a sequence number to remove a map sequence.
• Use the no keyword without a sequence number to remove the map.

Note While defining the VLAN access-map, you should use only single word as the access- map name and white spaces are not allowed in the access-map name. For example, you can use map_name to name the access-map, but you should not use multiple words such as map name. Effective from Cisco IOS release 12.2(33)SRE8, the length of the VLAN access-map name should not exceed 25 characters.

See the “VLAN Access Map Configuration and Verification Examples” section.

Configuring a Match Clause in a VLAN Access Map Sequence

To configure a match clause in a VLAN access map sequence, perform this task:

When configuring a match clause in a VLAN access map sequence, note the following information:

• You can select one or more ACLs.
• VACLs attached to WAN interfaces support only standard and extended Cisco IOS IP ACLs.
• Use the no keyword to remove a match clause or specified ACLs in the clause.
• For information about named MAC-Layer ACLs, refer to the “Configuring MAC ACLs” section.
• For information about Cisco IOS ACLs, refer to the Cisco IOS Security Configuration Guide, Release 12.2, “Traffic Filtering and Firewalls,” at this URL:

http://www.cisco.com/en/US/docs/ios/12_2/security/configuration/guide/scfacls.html

See the “VLAN Access Map Configuration and Verification Examples” section.

Sample Configuration for Match Clause

The following example shows the configuration of an IPV6 based match.

Configuring an Action Clause in a VLAN Access Map Sequence

To configure an action clause in a VLAN access map sequence, perform this task:

When configuring an action clause in a VLAN access map sequence, note the following information:

• You can set the action to drop, forward, forward capture, or redirect packets.
• VACLs applied to WAN interfaces support only the forward capture action. VACLs applied to WAN interfaces do not support the drop, forward, or redirect actions.
• Forwarded packets are still subject to any configured Cisco IOS security ACLs.
• The capture action sets the capture bit for the forwarded packets so that ports with the capture function enabled can receive the packets. Only forwarded packets can be captured. For more information about the capture action, see the “Configuring a Capture Port” section.
• VACLs applied to WAN interfaces do not support the log action.
• When the log action is specified, dropped packets are logged in software. Only dropped IP packets can be logged.
• The redirect action allows you to specify up to five interfaces, which can be physical interfaces or EtherChannels. You cannot specify packets to be redirected to an EtherChannel member or a VLAN interface.
• The redirect interface must be in the VLAN for which the VACL access map is configured.
• With a PFC3, if a VACL is redirecting traffic to an egress SPAN source port, SPAN does not copy the VACL-redirected traffic.
• SPAN and RSPAN destination ports transmit VACL-redirected traffic.
• Use the no keyword to remove an action clause or specified redirect interfaces.

See the “VLAN Access Map Configuration and Verification Examples” section.

Applying a VLAN Access Map

To apply a VLAN access map, perform this task:

When applying a VLAN access map, note the following information:

• You can apply the VLAN access map to one or more VLANs or WAN interfaces.
• The vlan_list parameter can be a single VLAN ID or a comma-separated list of VLAN IDs or VLAN ID ranges ( vlan_ID – vlan_ID).
• If you delete a WAN interface that has a VACL applied, the VACL configuration on the interface is also removed.
• You can apply only one VLAN access map to each VLAN or WAN interface.
• VACLs applied to VLANs are active only for VLANs with a Layer 3 VLAN interface configured. Applying a VLAN access map to a VLAN without a Layer 3 VLAN interface creates an administratively down Layer 3 VLAN interface to support the VLAN access map.
• VACLs applied to VLANs are inactive if the Layer 2 VLAN does not exist or is not operational.
• You cannot apply a VACL to a secondary private VLAN. VACLs applied to primary private VLANs also apply to secondary private VLANs.
• Use the no keyword to clear VLAN access maps from VLANs or WAN interfaces.

See the “VLAN Access Map Configuration and Verification Examples” section.

Verifying VLAN Access Map Configuration

To verify VLAN access map configuration, perform this task:

VLAN Access Map Configuration and Verification Examples

Assume IP-named ACL net_10 and any_host are defined as follows:

This example shows how to define and apply a VLAN access map to forward IP packets. In this example, IP traffic matching net_10 is forwarded and all other IP packets are dropped due to the default drop action. The map is applied to VLAN 12 to 16.

This example shows how to define and apply a VLAN access map to drop and log IP packets. In this example, IP traffic matching net_10 is dropped and logged and all other IP packets are forwarded:

This example shows how to define and apply a VLAN access map to forward and capture IP packets. In this example, IP traffic matching net_10 is forwarded and captured and all other IP packets are dropped:

Configuring a Capture Port

A port configured to capture VACL-filtered traffic is called a capture port.

Note To apply IEEE 802.1Q or ISL tags to the captured traffic, configure the capture port to trunk unconditionally (see the “Configuring the Layer 2 Switching Port as an ISL or 802.1Q Trunk” section and the “Configuring the Layer 2 Trunk Not to Use DTP” section).

To configure a capture port, perform this task:

When configuring a capture port, note the following information:

• You can configure any port as a capture port.
• The vlan_list parameter can be a single VLAN ID or a comma-separated list of VLAN IDs or VLAN ID ranges ( vlan_ID – vlan_ID).
• To encapsulate captured traffic, configure the capture port with the switchport trunk encapsulation command (see the “Configuring a Layer 2 Switching Port as a Trunk” section) before you enter the switchport capture command.
• For unencapsulated captured traffic, configure the capture port with the switchport mode access command (see the “Configuring a LAN Interface as a Layer 2 Access Port” section) before you enter the switchport capture command.
• The capture port supports only egress traffic. No traffic can enter the router through a capture port.
• LI overrides VACL Capture.
• VACL Capture and OAL are mutually exclusive features.
• When the VACL capture is configured on an egress interface with another egress feature that requires software processing of the traffic, packets of the overlapping traffic may be captured twice.

This example shows how to configure a Fast Ethernet interface 5/1 as a capture port:

This example shows how to display VLAN access map information:

This example shows how to display mappings between VACLs and VLANs. For each VACL map, there is information about the VLANs that the map is configured on and the VLANs that the map is active on. A VACL is not active if the VLAN does not have an interface.

Displaying IPv6 VACL Logging

To display the contents of the IPv6 VACL log table, use the following command:

show vlan access-log v6flow protocol {{src_addr src_mask} | any | {host {hostname | host_ip}}} {{dst_addr dst_mask} | any | {host {hostname | host_ip}}}[vlan vlan_id]

The following examples shows sample outputs for the command.