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Contents
- Configuring IPv4 ACLs
- Finding Feature Information
- Prerequisites for Configuring Network Security with ACLs
- Restrictions for Configuring Network Security with ACLs
- Information about Network Security with ACLs
- ACL Overview
- Access Control Entries
- ACL Supported Types
- Supported ACLs
- ACL Precedence
- Port ACLs
- Router ACLs
- VLAN Maps
- ACEs and Fragmented and Unfragmented Traffic
- Example: ACEs and Fragmented and Unfragmented Traffic
- ACLs and Switch Stacks
- Active Switch and ACL Functions
- Stack Member and ACL Functions
- Active Switch Failure and ACLs
- Standard and Extended IPv4 ACLs
- IPv4 ACL Switch Unsupported Features
- Access List Numbers
- Numbered Standard IPv4 ACLs
- Numbered Extended IPv4 ACLs
- Named IPv4 ACLs
- ACL Logging
- Hardware and Software Treatment of IP ACLs
- VLAN Map Configuration Guidelines
- VLAN Maps with Router ACLs
- VLAN Maps and Router ACL Configuration Guidelines
- VACL Logging
- Time Ranges for ACLs
- IPv4 ACL Interface Considerations
- How to Configure ACLs
- Configuring IPv4 ACLs
- Creating a Numbered Standard ACL
- Creating a Numbered Extended ACL
- Creating Named Standard ACLs
- Creating Extended Named ACLs
- Configuring Time Ranges for ACLs
- Applying an IPv4 ACL to a Terminal Line
- Applying an IPv4 ACL to an Interface
- Creating Named MAC Extended ACLs
- Applying a MAC ACL to a Layer 2 Interface
- Configuring VLAN Maps
- Creating a VLAN Map
- Applying a VLAN Map to a VLAN
- Monitoring IPv4 ACLs
- Configuration Examples for ACLs
- Examples: Using Time Ranges with ACLs
- Examples: Including Comments in ACLs
- IPv4 ACL Configuration Examples
- ACLs in a Small Networked Office
- Examples: ACLs in a Small Networked Office
- Example: Numbered ACLs
- Examples: Extended ACLs
- Examples: Named ACLs
- Examples: Time Range Applied to an IP ACL
- Examples: Commented IP ACL Entries
- Examples: ACL Logging
- Configuration Examples for ACLs and VLAN Maps
- Example: Creating an ACL and a VLAN Map to Deny a Packet
- Example: Creating an ACL and a VLAN Map to Permit a Packet
- Example: Default Action of Dropping IP Packets and Forwarding MAC Packets
- Example: Default Action of Dropping MAC Packets and Forwarding IP Packets
- Example: Default Action of Dropping All Packets
- Configuration Examples for Using VLAN Maps in Your Network
- Example: Wiring Closet Configuration
- Example: Restricting Access to a Server on Another VLAN
- Example: Denying Access to a Server on Another VLAN
- Configuration Examples of Router ACLs and VLAN Maps Applied to VLANs
- Example: ACLs and Switched Packets
- Example: ACLs and Bridged Packets
- Example: ACLs and Routed Packets
- Example: ACLs and Multicast Packets
- Additional References
Configuring IPv4 ACLs
- Finding Feature Information
- Prerequisites for Configuring Network Security with ACLs
- Restrictions for Configuring Network Security with ACLs
- Information about Network Security with ACLs
- How to Configure ACLs
- Monitoring IPv4 ACLs
- Configuration Examples for ACLs
- Additional References
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Restrictions for Configuring Network Security with ACLs
ACL Filtering
The following are restrictions on ACL filtering:
- If IEEE 802.1Q tunneling is configured on an interface, any IEEE 802.1Q encapsulated IP packets received on the tunnel port can be filtered by MAC ACLs, but not by IP ACLs. This is because the switch does not recognize the protocol inside the IEEE 802.1Q header. This restriction applies to router ACLs, port ACLs, and VLAN maps.
IPv4 ACL Network Interfaces
The following restrictions apply to IPv4 ACLs to network interfaces:
- When controlling access to an interface, you can use a named or numbered ACL.
- If you apply an ACL to a Layer 2 interface that is a member of a VLAN, the Layer 2 (port) ACL takes precedence over an input Layer 3 ACL applied to the VLAN interface or a VLAN map applied to the VLAN.
- If you apply an ACL to a Layer 3 interface and routing is not enabled on the switch, the ACL only filters packets that are intended for the CPU, such as SNMP, Telnet, or web traffic.
- You do not have to enable routing to apply ACLs to Layer 2 interfaces.
MAC ACLs on a Layer 2 Interface
After you create a MAC ACL, you can apply it to a Layer 2 interface to filter non-IP traffic coming in that interface. When you apply the MAC ACL, consider these guidelines:
- If you apply an ACL to a Layer 2 interface that is a member of a VLAN, the Layer 2 (port) ACL takes precedence over an input Layer 3 ACL applied to the VLAN interface or a VLAN map applied to the VLAN. Incoming packets received on the Layer 2 port are always filtered by the port ACL.
- You can apply no more than one IP access list and one MAC access list to the same Layer 2 interface. The IP access list filters only IP packets, and the MAC access list filters non-IP packets.
- A Layer 2 interface can have only one MAC access list. If you apply a MAC access list to a Layer 2 interface that has a MAC ACL configured, the new ACL replaces the previously configured one.
NoteThe mac access-group interface configuration command is only valid when applied to a physical Layer 2 interface. You cannot use the command on EtherChannel port channels.
Related Concepts
Information about Network Security with ACLs
This chapter describes how to configure network security on the switch by using access control lists (ACLs), which in commands and tables are also referred to as access lists.
- ACL Overview
- Supported ACLs
- ACEs and Fragmented and Unfragmented Traffic
- ACLs and Switch Stacks
- Standard and Extended IPv4 ACLs
- Hardware and Software Treatment of IP ACLs
- VLAN Map Configuration Guidelines
- VLAN Maps with Router ACLs
- VACL Logging
- Time Ranges for ACLs
- IPv4 ACL Interface Considerations
ACL Overview
Packet filtering can help limit network traffic and restrict network use by certain users or devices. ACLs filter traffic as it passes through a router or switch and permit or deny packets crossing specified interfaces or VLANs. An ACL is a sequential collection of permit and deny conditions that apply to packets. When a packet is received on an interface, the switch compares the fields in the packet against any applied ACLs to verify that the packet has the required permissions to be forwarded, based on the criteria specified in the access lists. One by one, it tests packets against the conditions in an access list. The first match decides whether the switch accepts or rejects the packets. Because the switch stops testing after the first match, the order of conditions in the list is critical. If no conditions match, the switch rejects the packet. If there are no restrictions, the switch forwards the packet; otherwise, the switch drops the packet. The switch can use ACLs on all packets it forwards, including packets bridged within a VLAN.
You configure access lists on a router or Layer 3 switch to provide basic security for your network. If you do not configure ACLs, all packets passing through the switch could be allowed onto all parts of the network. You can use ACLs to control which hosts can access different parts of a network or to decide which types of traffic are forwarded or blocked at router interfaces. For example, you can allow e-mail traffic to be forwarded but not Telnet traffic. ACLs can be configured to block inbound traffic, outbound traffic, or both.
ACL Supported Types
The switch supports IP ACLs and Ethernet (MAC) ACLs:
- IP ACLs filter IPv4 traffic, including TCP, User Datagram Protocol (UDP), Internet Group Management Protocol (IGMP), and Internet Control Message Protocol (ICMP).
- Ethernet ACLs filter non-IP traffic.
This switch also supports quality of service (QoS) classification ACLs.
Supported ACLs
The switch supports three types of ACLs to filter traffic:
- Port ACLs access-control traffic entering a Layer 2 interface. You can apply only one IP access list and one MAC access list to a Layer 2 interface.
- Router ACLs access-control routed traffic between VLANs and are applied to Layer 3 interfaces in a specific direction (inbound or outbound).
- VLAN ACLs or VLAN maps access-control all packets (bridged and routed). You can use VLAN maps to filter traffic between devices in the same VLAN. VLAN maps are configured to provide access control based on Layer 3 addresses for IPv4. Unsupported protocols are access-controlled through MAC addresses using Ethernet ACEs. After a VLAN map is applied to a VLAN, all packets (routed or bridged) entering the VLAN are checked against the VLAN map. Packets can either enter the VLAN through a switch port or through a routed port after being routed.
ACL Precedence
When Port ACLs, router ACLs, and VLAN maps are configured on the same switch, the filtering precedence, from greatest to least, is port ACL, router ACL, then VLAN map. The following examples describe simple use cases:
- When both an input port ACL and a VLAN map are applied, incoming packets received on ports with a port ACL applied are filtered by the port ACL. Other packets are filtered by the VLAN map
- When an input router ACL and input port ACL exist in a switch virtual interface (SVI), incoming packets received on ports to which a port ACL is applied are filtered by the port ACL. Incoming routed IP packets received on other ports are filtered by the router ACL. Other packets are not filtered.
- When an output router ACL and input port ACL exist in an SVI, incoming packets received on the ports to which a port ACL is applied are filtered by the port ACL. Outgoing routed IP packets are filtered by the router ACL. Other packets are not filtered.
- When a VLAN map, input router ACL, and input port ACL exist in an SVI, incoming packets received on the ports to which a port ACL is applied are only filtered by the port ACL. Incoming routed IP packets received on other ports are filtered by both the VLAN map and the router ACL. Other packets are filtered only by the VLAN map.
- When a VLAN map, output router ACL, and input port ACL exist in an SVI, incoming packets received on the ports to which a port ACL is applied are only filtered by the port ACL. Outgoing routed IP packets are filtered by both the VLAN map and the router ACL. Other packets are filtered only by the VLAN map.
Related References
Port ACLs
Port ACLs are ACLs that are applied to Layer 2 interfaces on a switch. Port ACLs are supported only on physical interfaces and not on EtherChannel interfaces. Port ACLs can be applied on outbound and inbound interfaces. The following access lists are supported:
- Standard IP access lists using source addresses
- Extended IP access lists using source and destination addresses and optional protocol type information
- MAC extended access lists using source and destination MAC addresses and optional protocol type information
The switch examines ACLs on an interface and permits or denies packet forwarding based on how the packet matches the entries in the ACL. In this way, ACLs control access to a network or to part of a network.
Figure 1. Using ACLs to Control Traffic in a Network. This is an example of using port ACLs to control access to a network when all workstations are in the same VLAN. ACLs applied at the Layer 2 input would allow Host A to access the Human Resources network, but prevent Host B from accessing the same network. Port ACLs can only be applied to Layer 2 interfaces in the inbound direction.When you apply a port ACL to a trunk port, the ACL filters traffic on all VLANs present on the trunk port. When you apply a port ACL to a port with voice VLAN, the ACL filters traffic on both data and voice VLANs.
With port ACLs, you can filter IP traffic by using IP access lists and non-IP traffic by using MAC addresses. You can filter both IP and non-IP traffic on the same Layer 2 interface by applying both an IP access list and a MAC access list to the interface.
Router ACLs
You can apply router ACLs on switch virtual interfaces (SVIs), which are Layer 3 interfaces to VLANs; on physical Layer 3 interfaces; and on Layer 3 EtherChannel interfaces. You apply router ACLs on interfaces for specific directions (inbound or outbound). You can apply one router ACL in each direction on an interface.
The switch supports these access lists for IPv4 traffic:
- Standard IP access lists use source addresses for matching operations.
- Extended IP access lists use source and destination addresses and optional protocol type information for matching operations.
As with port ACLs, the switch examines ACLs associated with features configured on a given interface. As packets enter the switch on an interface, ACLs associated with all inbound features configured on that interface are examined. After packets are routed and before they are forwarded to the next hop, all ACLs associated with outbound features configured on the egress interface are examined.
ACLs permit or deny packet forwarding based on how the packet matches the entries in the ACL, and can be used to control access to a network or to part of a network.
VLAN Maps
Use VLAN ACLs or VLAN maps to access-control all traffic. You can apply VLAN maps to all packets that are routed into or out of a VLAN or are bridged within a VLAN in the switch or switch stack.
Use VLAN maps for security packet filtering. VLAN maps are not defined by direction (input or output).
You can configure VLAN maps to match Layer 3 addresses for IPv4 traffic.
All non-IP protocols are access-controlled through MAC addresses and Ethertype using MAC VLAN maps. (IP traffic is not access controlled by MAC VLAN maps.) You can enforce VLAN maps only on packets going through the switch; you cannot enforce VLAN maps on traffic between hosts on a hub or on another switch connected to this switch.
With VLAN maps, forwarding of packets is permitted or denied, based on the action specified in the map.
ACEs and Fragmented and Unfragmented Traffic
IP packets can be fragmented as they cross the network. When this happens, only the fragment containing the beginning of the packet contains the Layer 4 information, such as TCP or UDP port numbers, ICMP type and code, and so on. All other fragments are missing this information.
Some access control entries (ACEs) do not check Layer 4 information and therefore can be applied to all packet fragments. ACEs that do test Layer 4 information cannot be applied in the standard manner to most of the fragments in a fragmented IP packet. When the fragment contains no Layer 4 information and the ACE tests some Layer 4 information, the matching rules are modified:
- Permit ACEs that check the Layer 3 information in the fragment (including protocol type, such as TCP, UDP, and so on) are considered to match the fragment regardless of what the missing Layer 4 information might have been.
- Deny ACEs that check Layer 4 information never match a fragment unless the fragment contains Layer 4 information.
Example: ACEs and Fragmented and Unfragmented Traffic
Consider access list 102, configured with these commands, applied to three fragmented packets:
Switch(config)# access-list 102 permit tcp any host 10.1.1.1 eq smtp Switch(config)# access-list 102 deny tcp any host 10.1.1.2 eq telnet Switch(config)# access-list 102 permit tcp any host 10.1.1.2 Switch(config)# access-list 102 deny tcp any any
- Packet A is a TCP packet from host 10.2.2.2., port 65000, going to host 10.1.1.1 on the SMTP port. If this packet is fragmented, the first fragment matches the first ACE (a permit) as if it were a complete packet because all Layer 4 information is present. The remaining fragments also match the first ACE, even though they do not contain the SMTP port information, because the first ACE only checks Layer 3 information when applied to fragments. The information in this example is that the packet is TCP and that the destination is 10.1.1.1.
- Packet B is from host 10.2.2.2, port 65001, going to host 10.1.1.2 on the Telnet port. If this packet is fragmented, the first fragment matches the second ACE (a deny) because all Layer 3 and Layer 4 information is present. The remaining fragments in the packet do not match the second ACE because they are missing Layer 4 information. Instead, they match the third ACE (a permit). Because the first fragment was denied, host 10.1.1.2 cannot reassemble a complete packet, so packet B is effectively denied. However, the later fragments that are permitted will consume bandwidth on the network and resources of host 10.1.1.2 as it tries to reassemble the packet.
- Fragmented packet C is from host 10.2.2.2, port 65001, going to host 10.1.1.3, port ftp. If this packet is fragmented, the first fragment matches the fourth ACE (a deny). All other fragments also match the fourth ACE because that ACE does not check any Layer 4 information and because Layer 3 information in all fragments shows that they are being sent to host 10.1.1.3, and the earlier permit ACEs were checking different hosts.
ACLs and Switch Stacks
ACL support is the same for a switch stack as for a standalone switch. ACL configuration information is propagated to all switches in the stack. All switches in the stack, including the active switch, process the information and program their hardware.
Active Switch and ACL Functions
The active switch performs these ACL functions:
- It processes the ACL configuration and propagates the information to all stack members.
- It distributes the ACL information to any switch that joins the stack.
- If packets must be forwarded by software for any reason (for example, not enough hardware resources), the active switch forwards the packets only after applying ACLs on the packets.
- It programs its hardware with the ACL information it processes.
Standard and Extended IPv4 ACLs
This section describes IP ACLs.
An ACL is a sequential collection of permit and deny conditions. One by one, the switch tests packets against the conditions in an access list. The first match determines whether the switch accepts or rejects the packet. Because the switch stops testing after the first match, the order of the conditions is critical. If no conditions match, the switch denies the packet.
The software supports these types of ACLs or access lists for IPv4:
- IPv4 ACL Switch Unsupported Features
- Access List Numbers
- Numbered Standard IPv4 ACLs
- Numbered Extended IPv4 ACLs
- Named IPv4 ACLs
- ACL Logging
IPv4 ACL Switch Unsupported Features
Access List Numbers
The number you use to denote your ACL shows the type of access list that you are creating.
This lists the access-list number and corresponding access list type and shows whether or not they are supported in the switch. The switch supports IPv4 standard and extended access lists, numbers 1 to 199 and 1300 to 2699.
Table 1 Access List NumbersIn addition to numbered standard and extended ACLs, you can also create standard and extended named IP ACLs by using the supported numbers. That is, the name of a standard IP ACL can be 1 to 99; the name of an extended IP ACL can be 100 to 199. The advantage of using named ACLs instead of numbered lists is that you can delete individual entries from a named list.
Numbered Standard IPv4 ACLs
When creating an ACL, remember that, by default, the end of the ACL contains an implicit deny statement for all packets that it did not find a match for before reaching the end. With standard access lists, if you omit the mask from an associated IP host address ACL specification, 0.0.0.0 is assumed to be the mask.
The switch always rewrites the order of standard access lists so that entries with host matches and entries with matches having a don’t care mask of 0.0.0.0 are moved to the top of the list, above any entries with non-zero don’t care masks. Therefore, in show command output and in the configuration file, the ACEs do not necessarily appear in the order in which they were entered.
After creating a numbered standard IPv4 ACL, you can apply it to terminal lines, to interfaces, or to VLANs.
Numbered Extended IPv4 ACLs
Although standard ACLs use only source addresses for matching, you can use extended ACL source and destination addresses for matching operations and optional protocol type information for finer granularity of control. When you are creating ACEs in numbered extended access lists, remember that after you create the ACL, any additions are placed at the end of the list. You cannot reorder the list or selectively add or remove ACEs from a numbered list.
The switch does not support dynamic or reflexive access lists. It also does not support filtering based on the type of service (ToS) minimize-monetary-cost bit.
Some protocols also have specific parameters and keywords that apply to that protocol.
You can define an extended TCP, UDP, ICMP, IGMP, or other IP ACL. The switch also supports these IP protocols:
NoteICMP echo-reply cannot be filtered. All other ICMP codes or types can be filtered.
These IP protocols are supported:
- Authentication Header Protocol (ahp)
- Encapsulation Security Payload (esp)
- Enhanced Interior Gateway Routing Protocol (eigrp)
- generic routing encapsulation (gre)
- Internet Control Message Protocol (icmp)
- Internet Group Management Protocol (igmp)
- any Interior Protocol (ip)
- IP in IP tunneling (ipinip)
- KA9Q NOS-compatible IP over IP tunneling (nos)
- Open Shortest Path First routing (ospf)
- Payload Compression Protocol (pcp)
- Protocol-Independent Multicast (pim)
- Transmission Control Protocol (tcp)
- User Datagram Protocol (udp)
Named IPv4 ACLs
You can identify IPv4 ACLs with an alphanumeric string (a name) rather than a number. You can use named ACLs to configure more IPv4 access lists in a router than if you were to use numbered access lists. If you identify your access list with a name rather than a number, the mode and command syntax are slightly different. However, not all commands that use IP access lists accept a named access list.
Consider these guidelines and limitations before configuring named ACLs:
- Not all commands that accept a numbered ACL accept a named ACL. ACLs for packet filters and route filters on interfaces can use a name. VLAN maps also accept a name.
- A standard ACL and an extended ACL cannot have the same name.
- Numbered ACLs are also available.
- You can use standard or extended ACLs (named or numbered) in VLAN maps.
ACL Logging
The switch software can provide logging messages about packets permitted or denied by a standard IP access list. That is, any packet that matches the ACL causes an informational logging message about the packet to be sent to the console. The level of messages logged to the console is controlled by the logging console commands controlling the syslog messages.
The first packet that triggers the ACL causes a logging message right away, and subsequent packets are collected over 5-minute intervals before they appear or logged. The logging message includes the access list number, whether the packet was permitted or denied, the source IP address of the packet, and the number of packets from that source permitted or denied in the prior 5-minute interval.
Hardware and Software Treatment of IP ACLs
ACL processing is performed in hardware. If the hardware reaches its capacity to store ACL configurations, all packets on that interface are dropped.
NoteIf an ACL configuration cannot be implemented in hardware due to an out-of-resource condition on a switch or stack member, then only the traffic in that VLAN arriving on that switch is affected.
For router ACLs, other factors can cause packets to be sent to the CPU:
When traffic flows are both logged and forwarded, forwarding is done by hardware, but logging must be done by software. Because of the difference in packet handling capacity between hardware and software, if the sum of all flows being logged (both permitted flows and denied flows) is of great enough bandwidth, not all of the packets that are forwarded can be logged.
When you enter the show ip access-lists privileged EXEC command, the match count displayed does not account for packets that are access controlled in hardware. Use the show platform acl counters hardware privileged EXEC command to obtain some basic hardware ACL statistics for switched and routed packets.
Router ACLs function as follows:
- The hardware controls permit and deny actions of standard and extended ACLs (input and output) for security access control.
- If log has not been specified, the flows that match a deny statement in a security ACL are dropped by the hardware if ip unreachables is disabled. The flows matching a permit statement are switched in hardware.
- Adding the log keyword to an ACE in a router ACL causes a copy of the packet to be sent to the CPU for logging only. If the ACE is a permit statement, the packet is still switched and routed in hardware.
VLAN Map Configuration Guidelines
VLAN maps are the only way to control filtering within a VLAN. VLAN maps have no direction. To filter traffic in a specific direction by using a VLAN map, you need to include an ACL with specific source or destination addresses. If there is a match clause for that type of packet (IP or MAC) in the VLAN map, the default action is to drop the packet if the packet does not match any of the entries within the map. If there is no match clause for that type of packet, the default is to forward the packet.
The following are the VLAN map configuration guidelines:
- If there is no ACL configured to deny traffic on an interface and no VLAN map is configured, all traffic is permitted.
- Each VLAN map consists of a series of entries. The order of entries in an VLAN map is important. A packet that comes into the switch is tested against the first entry in the VLAN map. If it matches, the action specified for that part of the VLAN map is taken. If there is no match, the packet is tested against the next entry in the map.
- If the VLAN map has at least one match clause for the type of packet (IP or MAC) and the packet does not match any of these match clauses, the default is to drop the packet. If there is no match clause for that type of packet in the VLAN map, the default is to forward the packet.
- Logging is not supported for VLAN maps.
- When a switch has an IP access list or MAC access list applied to a Layer 2 interface, and you apply a VLAN map to a VLAN that the port belongs to, the port ACL takes precedence over the VLAN map.
- If a VLAN map configuration cannot be applied in hardware, all packets in that VLAN are dropped.
VLAN Maps with Router ACLs
To access control both bridged and routed traffic, you can use VLAN maps only or a combination of router ACLs and VLAN maps. You can define router ACLs on both input and output routed VLAN interfaces, and you can define a VLAN map to access control the bridged traffic.
If a packet flow matches a VLAN-map deny clause in the ACL, regardless of the router ACL configuration, the packet flow is denied.
NoteWhen you use router ACLs with VLAN maps, packets that require logging on the router ACLs are not logged if they are denied by a VLAN map.
If the VLAN map has a match clause for the type of packet (IP or MAC) and the packet does not match the type, the default is to drop the packet. If there is no match clause in the VLAN map, and no action specified, the packet is forwarded if it does not match any VLAN map entry.
VLAN Maps and Router ACL Configuration Guidelines
These guidelines are for configurations where you need to have an router ACL and a VLAN map on the same VLAN. These guidelines do not apply to configurations where you are mapping router ACLs and VLAN maps on different VLANs.
If you must configure a router ACL and a VLAN map on the same VLAN, use these guidelines for both router ACL and VLAN map configuration:
- You can configure only one VLAN map and one router ACL in each direction (input/output) on a VLAN interface.
- Whenever possible, try to write the ACL with all entries having a single action except for the final, default action of the other type. That is, write the ACL using one of these two forms: permit... permit... permit... deny ip any any or deny... deny... deny... permit ip any any
- To define multiple actions in an ACL (permit, deny), group each action type together to reduce the number of entries.
- Avoid including Layer 4 information in an ACL; adding this information complicates the merging process. The best merge results are obtained if the ACLs are filtered based on IP addresses (source and destination) and not on the full flow (source IP address, destination IP address, protocol, and protocol ports). It is also helpful to use don’t care bits in the IP address, whenever possible. If you need to specify the full-flow mode and the ACL contains both IP ACEs and TCP/UDP/ICMP ACEs with Layer 4 information, put the Layer 4 ACEs at the end of the list. This gives priority to the filtering of traffic based on IP addresses.
VACL Logging
When you configure VACL logging, syslog messages are generated for denied IP packets under these circumstances:
- When the first matching packet is received.
- For any matching packets received within the last 5 minutes.
- If the threshold is reached before the 5-minute interval.
Log messages are generated on a per-flow basis. A flow is defined as packets with the same IP addresses and Layer 4 (UDP or TCP) port numbers. If a flow does not receive any packets in the 5-minute interval, that flow is removed from the cache. When a syslog message is generated, the timer and packet counter are reset.
Time Ranges for ACLs
You can selectively apply extended ACLs based on the time of day and the week by using the time-range global configuration command. First, define a time-range name and set the times and the dates or the days of the week in the time range. Then enter the time-range name when applying an ACL to set restrictions to the access list. You can use the time range to define when the permit or deny statements in the ACL are in effect, for example, during a specified time period or on specified days of the week. The time-range keyword and argument are referenced in the named and numbered extended ACL task tables.
These are some benefits of using time ranges:
- You have more control over permitting or denying a user access to resources, such as an application (identified by an IP address/mask pair and a port number).
- You can control logging messages. ACL entries can be set to log traffic only at certain times of the day. Therefore, you can simply deny access without needing to analyze many logs generated during peak hours.
Time-based access lists trigger CPU activity because the new configuration of the access list must be merged with other features and the combined configuration loaded into the hardware memory. For this reason, you should be careful not to have several access lists configured to take affect in close succession (within a small number of minutes of each other.)
NoteThe time range relies on the switch system clock; therefore, you need a reliable clock source. We recommend that you use Network Time Protocol (NTP) to synchronize the switch clock.
Related Tasks
IPv4 ACL Interface Considerations
When you apply the ip access-group interface configuration command to a Layer 3 interface (an SVI, a Layer 3 EtherChannel, or a routed port), the interface must have been configured with an IP address. Layer 3 access groups filter packets that are routed or are received by Layer 3 processes on the CPU. They do not affect packets bridged within a VLAN.
For inbound ACLs, after receiving a packet, the switch checks the packet against the ACL. If the ACL permits the packet, the switch continues to process the packet. If the ACL rejects the packet, the switch discards the packet.
For outbound ACLs, after receiving and routing a packet to a controlled interface, the switch checks the packet against the ACL. If the ACL permits the packet, the switch sends the packet. If the ACL rejects the packet, the switch discards the packet.
By default, the input interface sends ICMP Unreachable messages whenever a packet is discarded, regardless of whether the packet was discarded because of an ACL on the input interface or because of an ACL on the output interface. ICMP Unreachables are normally limited to no more than one every one-half second per input interface, but this can be changed by using the ip icmp rate-limit unreachable global configuration command.
When you apply an undefined ACL to an interface, the switch acts as if the ACL has not been applied to the interface and permits all packets. Remember this behavior if you use undefined ACLs for network security.
Related Tasks
Related References
How to Configure ACLs
- Configuring IPv4 ACLs
- Creating a Numbered Standard ACL
- Creating a Numbered Extended ACL
- Creating Named Standard ACLs
- Creating Extended Named ACLs
- Configuring Time Ranges for ACLs
- Applying an IPv4 ACL to a Terminal Line
- Applying an IPv4 ACL to an Interface
- Creating Named MAC Extended ACLs
- Applying a MAC ACL to a Layer 2 Interface
- Configuring VLAN Maps
- Creating a VLAN Map
- Applying a VLAN Map to a VLAN
Configuring IPv4 ACLs
Creating a Numbered Standard ACL
SUMMARY STEPS
DETAILED STEPSRelated Tasks
Creating a Numbered Extended ACL
SUMMARY STEPS
2. access-list access-list-number {deny | permit} protocol source source-wildcard destination destination-wildcard [precedence precedence] [tos tos] [fragments] [log [log-input] [time-range time-range-name] [dscp dscp]
3. access-list access-list-number {deny | permit} tcp source source-wildcard [operator port] destination destination-wildcard [operator port] [established] [precedence precedence] [tos tos] [fragments] [log [log-input] ] [time-range time-range-name] [dscp dscp] [flag]
4. access-list access-list-number {deny | permit} udp source source-wildcard [operator port] destination destination-wildcard [operator port] [precedence precedence] [tos tos] [fragments] [log [log-input] ] [time-range time-range-name] [dscp dscp]
5. access-list access-list-number {deny | permit} icmp source source-wildcard destination destination-wildcard [icmp-type | [[icmp-type icmp-code] | [icmp-message]] [precedence precedence] [tos tos] [fragments] [log [log-input] ] [time-range time-range-name] [dscp dscp]
6. access-list access-list-number {deny | permit} igmp source source-wildcard destination destination-wildcard [igmp-type] [precedence precedence] [tos tos] [fragments] [log [log-input] ] [time-range time-range-name] [dscp dscp]
DETAILED STEPS
Command or Action Purpose
Step 1 configure terminal
Example:Switch# configure terminalStep 2 access-list access-list-number {deny | permit} protocol source source-wildcard destination destination-wildcard [precedence precedence] [tos tos] [fragments] [log [log-input] [time-range time-range-name] [dscp dscp]
Example:Switch(config)# access-list 101 permit ip host 10.1.1.2 any precedence 0 tos 0 logDefines an extended IPv4 access list and the access conditions.
The access-list-number is a decimal number from 100 to 199 or 2000 to 2699.
Enter deny or permit to specify whether to deny or permit the packet if conditions are matched.
For protocol, enter the name or number of an P protocol: ahp, eigrp, esp, gre, icmp, igmp, igrp, ip, ipinip, nos, ospf, pcp, pim, tcp, or udp, or an integer in the range 0 to 255 representing an IP protocol number. To match any Internet protocol (including ICMP, TCP, and UDP), use the keyword ip.
The source is the number of the network or host from which the packet is sent.
The source-wildcard applies wildcard bits to the source.
The destination is the network or host number to which the packet is sent.
The destination-wildcard applies wildcard bits to the destination.
Source, source-wildcard, destination, and destination-wildcard can be specified as:
- The 32-bit quantity in dotted-decimal format.
- The keyword any for 0.0.0.0 255.255.255.255 (any host).
- The keyword host for a single host 0.0.0.0.
The other keywords are optional and have these meanings:
- precedence—Enter to match packets with a precedence level specified as a number from 0 to 7 or by name: routine (0), priority (1), immediate (2), flash (3), flash-override (4), critical (5), internet (6), network (7).
- fragments—Enter to check non-initial fragments.
- tos—Enter to match by type of service level, specified by a number from 0 to 15 or a name: normal (0), max-reliability (2), max-throughput (4), min-delay (8).
- log—Enter to create an informational logging message to be sent to the console about the packet that matches the entry or log-input to include the input interface in the log entry.
- time-range—Specify the time-range name.
- dscp—Enter to match packets with the DSCP value specified by a number from 0 to 63, or use the question mark (?) to see a list of available values.
Note If you enter a dscp value, you cannot enter tos or precedence. You can enter both a tos and a precedence value with no dscp.
Step 3 access-list access-list-number {deny | permit} tcp source source-wildcard [operator port] destination destination-wildcard [operator port] [established] [precedence precedence] [tos tos] [fragments] [log [log-input] ] [time-range time-range-name] [dscp dscp] [flag]
Example:Switch(config)# access-list 101 permit tcp any any eq 500Defines an extended TCP access list and the access conditions.
The parameters are the same as those described for an extended IPv4 ACL, with these exceptions:
(Optional) Enter an operator and port to compare source (if positioned after source source-wildcard) or destination (if positioned after destination destination-wildcard) port. Possible operators include eq (equal), gt (greater than), lt (less than), neq (not equal), and range (inclusive range). Operators require a port number (range requires two port numbers separated by a space).
Enter the port number as a decimal number (from 0 to 65535) or the name of a TCP port.
Step 4 access-list access-list-number {deny | permit} udp source source-wildcard [operator port] destination destination-wildcard [operator port] [precedence precedence] [tos tos] [fragments] [log [log-input] ] [time-range time-range-name] [dscp dscp]
Example:Switch(config)# access-list 101 permit udp any any eq 100(Optional) Defines an extended UDP access list and the access conditions.
The UDP parameters are the same as those described for TCP except that the [operator [port]] port number or name must be a UDP port number or name, and the flag and established keywords are not valid for UDP.
Step 5 access-list access-list-number {deny | permit} icmp source source-wildcard destination destination-wildcard [icmp-type | [[icmp-type icmp-code] | [icmp-message]] [precedence precedence] [tos tos] [fragments] [log [log-input] ] [time-range time-range-name] [dscp dscp]
Example:Switch(config)# access-list 101 permit icmp any any 200Defines an extended ICMP access list and the access conditions.
The ICMP parameters are the same as those described for most IP protocols in an extended IPv4 ACL, with the addition of the ICMP message type and code parameters. These optional keywords have these meanings:
Step 6 access-list access-list-number {deny | permit} igmp source source-wildcard destination destination-wildcard [igmp-type] [precedence precedence] [tos tos] [fragments] [log [log-input] ] [time-range time-range-name] [dscp dscp]
Example:Switch(config)# access-list 101 permit igmp any any 14(Optional) Defines an extended IGMP access list and the access conditions.
The IGMP parameters are the same as those described for most IP protocols in an extended IPv4 ACL, with this optional parameter.
igmp-type—To match IGMP message type, enter a number from 0 to 15, or enter the message name: dvmrp, host-query, host-report, pim, or trace.
Step 7 end
Example:Switch(config)# endExtended IP ACL with the any Keyword
To use an abbreviation for a source and source wildcard of 0.0.0.0 255.255.255.255 and an abbreviation for a destination and destination wildcard of 0.0.0.0 255.255.255.255 when defining an extended IP ACL, use the any keyword in place of source and destination address and wildcard:
Switch# configure terminal Switch(config)# access-list 101 permit ip any any precedence 0 tos 0 fragments log time-range workhours dscp 10 Switch(config)# endTo use an abbreviation for a source and a source wildcard of source 0.0.0.0 and an abbreviation for a destination and destination wildcard of destination 0.0.0.0 when defining an extended IP ACL, use the host keyword in place of the source and destination wildcard or mask.
Switch# configure terminal Switch(config)# access-list 101 permit ip host 10.1.1.2 any Switch(config)# endRelated Tasks
Creating Named Standard ACLs
SUMMARY STEPS
DETAILED STEPS
Command or Action Purpose
Step 1 configure terminal
Example:Switch# configure terminalStep 2 ip access-list standard name
Example:Switch(config)# ip access-list standard 20Defines a standard IPv4 access list using a name, and enter access-list configuration mode.
Step 3 Use one of the following:
- deny {source [source-wildcard] | host source | any} [log]
- permit {source [source-wildcard] | host source | any} [log]]
Example:Switch(config-std-nacl)# deny 192.168.0.0 0.0.255.255 255.255.0.0 0.0.255.255Switch(config-std-nacl)# permit 10.108.0.0 0.0.0.0 255.255.255.0 0.0.0.0In access-list configuration mode, specify one or more conditions denied or permitted to decide if the packet is forwarded or dropped.
Step 4 end
Example:Switch(config-std-nacl)# endCreating Extended Named ACLs
SUMMARY STEPS
2. ip access-list extended name
3. {deny | permit} protocol {source [source-wildcard] | host source | any} {destination [destination-wildcard] | host destination | any} [precedence precedence] [tos tos] [established] [log] [time-range time-range-name]
DETAILED STEPS
Command or Action Purpose
Step 1 configure terminal
Example:Switch# configure terminalStep 2 ip access-list extended name
Example:Switch(config)# ip access-list extended 150Defines an extended IPv4 access list using a name, and enter access-list configuration mode.
Step 3 {deny | permit} protocol {source [source-wildcard] | host source | any} {destination [destination-wildcard] | host destination | any} [precedence precedence] [tos tos] [established] [log] [time-range time-range-name]
Example:Switch(config-ext-nacl)# permit 0 any anyIn access-list configuration mode, specify the conditions allowed or denied. Use the log keyword to get access list logging messages, including violations.
Step 4 end
Example:Switch(config-ext-nacl)# endWhen you are creating extended ACLs, remember that, by default, the end of the ACL contains an implicit deny statement for everything if it did not find a match before reaching the end. For standard ACLs, if you omit the mask from an associated IP host address access list specification, 0.0.0.0 is assumed to be the mask.
After you create an ACL, any additions are placed at the end of the list. You cannot selectively add ACL entries to a specific ACL. However, you can use no permit and no deny access-list configuration mode commands to remove entries from a named ACL. This example shows how you can delete individual ACEs from the named access list border-list:
Switch(config)# ip access-list extended border-list Switch(config-ext-nacl)# no permit ip host 10.1.1.3 anyBeing able to selectively remove lines from a named ACL is one reason you might use named ACLs instead of numbered ACLs.
What to Do NextAfter creating a named ACL, you can apply it to interfaces or to VLANs .
Configuring Time Ranges for ACLs
SUMMARY STEPSBeginning in privileged EXEC mode, follow these steps to configure a time-range parameter for an ACL:
DETAILED STEPSWhat to Do Next
Command or Action Purpose
Step 1 configure terminal
Example:Switch# configure terminalStep 2 time-range time-range-name
Example:Switch(config)# time-range workhoursAssigns a meaningful name (for example, workhours) to the time range to be created, and enter time-range configuration mode. The name cannot contain a space or quotation mark and must begin with a letter.
Step 3 Use one of the following:
- absolute [start time date] [end time date]
- periodic day-of-the-week hh:mm to [day-of-the-week] hh:mm
- periodic {weekdays | weekend | daily} hh:mm to hh:mm
Example:Switch(config-time-range)# absolute start 00:00 1 Jan 2006 end 23:59 1 Jan 2006Switch(config-time-range)# periodic weekdays 8:00 to 12:00Specifies when the function it will be applied to is operational.
Step 4 end
Example:Switch(config)# endRepeat the steps if you have multiple items that you want in effect at different times.
Related Concepts
Applying an IPv4 ACL to a Terminal Line
SUMMARY STEPSYou can use numbered ACLs to control access to one or more terminal lines. You cannot apply named ACLs to lines. You must set identical restrictions on all the virtual terminal lines because a user can attempt to connect to any of them.
Beginning in privileged EXEC mode, follow these steps to restrict incoming and outgoing connections between a virtual terminal line and the addresses in an ACL:
DETAILED STEPS
Command or Action Purpose
Step 1 configure terminal
Example:Switch# configure terminalStep 2 line [console | vty] line-number
Example:Switch(config)# line console 0Identifies a specific line to configure, and enter in-line configuration mode.
- console—Specifies the console terminal line. The console port is DCE.
- vty—Specifies a virtual terminal for remote console access.
The line-number is the first line number in a contiguous group that you want to configure when the line type is specified. The range is from 0 to 16.
Step 3 access-class access-list-number {in | out}
Example:Switch(config-line)# access-class 10 inRestricts incoming and outgoing connections between a particular virtual terminal line (into a device) and the addresses in an access list.
Step 4 end
Example:Switch(config-line)# endStep 5 show running-config
Example:Switch# show running-configStep 6 copy running-config startup-config
Example:Switch# copy running-config startup-configApplying an IPv4 ACL to an Interface
SUMMARY STEPSThis section describes how to apply IPv4 ACLs to network interfaces.
Beginning in privileged EXEC mode, follow these steps to control access to an interface:
DETAILED STEPS
Command or Action Purpose
Step 1 configure terminal
Example:Switch# configure terminalStep 2 interface interface-id
Example:Switch(config)# interface gigabitethernet1/0/1Identifies a specific interface for configuration, and enter interface configuration mode.
The interface can be a Layer 2 interface (port ACL), or a Layer 3 interface (router ACL).
Step 3 ip access-group {access-list-number | name} {in | out}
Example:Switch(config-if)# ip access-group 2 inControls access to the specified interface.
The out keyword is not supported for Layer 2 interfaces (port ACLs).
Step 4 end
Example:Switch(config-if)# endStep 5 show running-config
Example:Switch# show running-configStep 6 copy running-config startup-config
Example:Switch# copy running-config startup-config
Related References
Creating Named MAC Extended ACLs
SUMMARY STEPSYou can filter non-IPv4 traffic on a VLAN or on a Layer 2 interface by using MAC addresses and named MAC extended ACLs. The procedure is similar to that of configuring other extended named ACLs.
Beginning in privileged EXEC mode, follow these steps to create a named MAC extended ACL:
2. mac access-list extended name
3. {deny | permit} {any | host source MAC address | source MAC address mask} {any | host destination MAC address | destination MAC address mask} [type mask | lsap lsap mask | aarp | amber | dec-spanning | decnet-iv | diagnostic | dsm | etype-6000 | etype-8042 | lat | lavc-sca | mop-console | mop-dump | msdos | mumps | netbios | vines-echo | vines-ip | xns-idp | 0-65535] [cos cos]
DETAILED STEPS
Command or Action Purpose
Step 1 configure terminal
Example:Switch# configure terminalStep 2 mac access-list extended name
Example:Switch(config)# mac access-list extended mac1Step 3 {deny | permit} {any | host source MAC address | source MAC address mask} {any | host destination MAC address | destination MAC address mask} [type mask | lsap lsap mask | aarp | amber | dec-spanning | decnet-iv | diagnostic | dsm | etype-6000 | etype-8042 | lat | lavc-sca | mop-console | mop-dump | msdos | mumps | netbios | vines-echo | vines-ip | xns-idp | 0-65535] [cos cos]
Example:Switch(config-ext-macl)# deny any any decnet-ivor
Switch(config-ext-macl)# permit any anyIn extended MAC access-list configuration mode, specifies to permit or deny any source MAC address, a source MAC address with a mask, or a specific host source MAC address and any destination MAC address, destination MAC address with a mask, or a specific destination MAC address.
(Optional) You can also enter these options:
- type mask—An arbitrary EtherType number of a packet with Ethernet II or SNAP encapsulation in decimal, hexadecimal, or octal with optional mask of don’t care bits applied to the EtherType before testing for a match.
- lsap lsap mask—An LSAP number of a packet with IEEE 802.2 encapsulation in decimal, hexadecimal, or octal with optional mask of don’t care bits.
- aarp | amber | dec-spanning | decnet-iv | diagnostic | dsm | etype-6000 | etype-8042 | lat | lavc-sca | mop-console | mop-dump | msdos | mumps | netbios | vines-echo | vines-ip | xns-idp—A non-IP protocol.
- cos cos—An IEEE 802.1Q cost of service number from 0 to 7 used to set priority.
Step 4 end
Example:Switch(config-ext-macl)# end
Related References
Applying a MAC ACL to a Layer 2 Interface
SUMMARY STEPSBeginning in privileged EXEC mode, follow these steps to apply a MAC access list to control access to a Layer 2 interface:
DETAILED STEPS
Command or Action Purpose
Step 1 configure terminal
Example:Switch# configure terminalStep 2 interface interface-id
Example:Switch(config)# interface gigabitethernet1/0/2Identifies a specific interface, and enter interface configuration mode. The interface must be a physical Layer 2 interface (port ACL).
Step 3 mac access-group {name} {in | out }
Example:Switch(config-if)# mac access-group mac1 inControls access to the specified interface by using the MAC access list.
Port ACLs are supported in the outbound and inbound directions.
Step 4 end
Example:Switch(config-if)# endStep 5 show mac access-group [interface interface-id]
Example:Switch# show mac access-group interface gigabitethernet1/0/2Displays the MAC access list applied to the interface or all Layer 2 interfaces.
Step 6 copy running-config startup-config
Example:Switch# copy running-config startup-configAfter receiving a packet, the switch checks it against the inbound ACL. If the ACL permits it, the switch continues to process the packet. If the ACL rejects the packet, the switch discards it. When you apply an undefined ACL to an interface, the switch acts as if the ACL has not been applied and permits all packets. Remember this behavior if you use undefined ACLs for network security.
Related References
Configuring VLAN Maps
Before You BeginSUMMARY STEPSCreate the standard or extended IPv4 ACLs or named MAC extended ACLs that you want to apply to the VLAN.
1. vlan access-map name [number]
2. match {ip | mac} address {name | number} [name | number]
3. Enter one of the following commands to specify an IP packet or a non-IP packet (with only a known MAC address) and to match the packet against one or more ACLs (standard or extended):
DETAILED STEPS
Command or Action Purpose
Step 1 vlan access-map name [number]
Example:Switch(config)# vlan access-map map_1 20Creates a VLAN map, and give it a name and (optionally) a number. The number is the sequence number of the entry within the map.
When you create VLAN maps with the same name, numbers are assigned sequentially in increments of 10. When modifying or deleting maps, you can enter the number of the map entry that you want to modify or delete.
VLAN maps do not use the specific permit or deny keywords. To deny a packet by using VLAN maps, create an ACL that would match the packet, and set the action to drop. A permit in the ACL counts as a match. A deny in the ACL means no match.
Entering this command changes to access-map configuration mode.
Step 2 match {ip | mac} address {name | number} [name | number]
Example:Switch(config-access-map)# match ip address ip2Match the packet (using either the IP or MAC address) against one or more standard or extended access lists. Note that packets are only matched against access lists of the correct protocol type. IP packets are matched against standard or extended IP access lists. Non-IP packets are only matched against named MAC extended access lists.
Note If the VLAN map is configured with a match clause for a type of packet (IP or MAC) and the map action is drop, all packets that match the type are dropped. If the VLAN map has no match clause, and the configured action is drop, all IP and Layer 2 packets are dropped.
Step 3 Enter one of the following commands to specify an IP packet or a non-IP packet (with only a known MAC address) and to match the packet against one or more ACLs (standard or extended): Sets the action for the map entry.
Step 4 vlan filter mapname vlan-list list
Example:Switch(config)# vlan filter map 1 vlan-list 20-22Applies the VLAN map to one or more VLAN IDs.
The list can be a single VLAN ID (22), a consecutive list (10-22), or a string of VLAN IDs (12, 22, 30). Spaces around the comma and hyphen are optional.
Creating a VLAN Map
SUMMARY STEPSEach VLAN map consists of an ordered series of entries. Beginning in privileged EXEC mode, follow these steps to create, add to, or delete a VLAN map entry:
DETAILED STEPS
Command or Action Purpose
Step 1 configure terminal
Example:Switch# configure terminalStep 2 vlan access-map name [number]
Example:Switch(config)# vlan access-map map_1 20Creates a VLAN map, and give it a name and (optionally) a number. The number is the sequence number of the entry within the map.
When you create VLAN maps with the same name, numbers are assigned sequentially in increments of 10. When modifying or deleting maps, you can enter the number of the map entry that you want to modify or delete.
VLAN maps do not use the specific permit or deny keywords. To deny a packet by using VLAN maps, create an ACL that would match the packet, and set the action to drop. A permit in the ACL counts as a match. A deny in the ACL means no match.
Entering this command changes to access-map configuration mode.
Step 3 match {ip | mac} address {name | number} [name | number]
Example:Switch(config-access-map)# match ip address ip2Match the packet (using either the IP or MAC address) against one or more standard or extended access lists. Note that packets are only matched against access lists of the correct protocol type. IP packets are matched against standard or extended IP access lists. Non-IP packets are only matched against named MAC extended access lists.
Step 4 action {drop | forward}
Example:Switch(config-access-map)# action forward(Optional) Sets the action for the map entry. The default is to forward.
Step 5 end
Example:Switch(config-access-map)# endStep 6 show running-config
Example:Switch# show running-configStep 7 copy running-config startup-config
Example:Switch# copy running-config startup-config
Applying a VLAN Map to a VLAN
SUMMARY STEPS
DETAILED STEPS
Command or Action Purpose
Step 1 configure terminal
Example:Switch# configure terminalStep 2 vlan filter mapname vlan-list list
Example:Switch(config)# vlan filter map 1 vlan-list 20-22Applies the VLAN map to one or more VLAN IDs.
The list can be a single VLAN ID (22), a consecutive list (10-22), or a string of VLAN IDs (12, 22, 30). Spaces around the comma and hyphen are optional.
Step 3 end
Example:Switch(config)# endStep 4 show running-config
Example:Switch# show running-configStep 5 copy running-config startup-config
Example:Switch# copy running-config startup-config
Monitoring IPv4 ACLs
You can monitor IPv4 ACLs by displaying the ACLs that are configured on the switch, and displaying the ACLs that have been applied to interfaces and VLANs.
When you use the ip access-group interface configuration command to apply ACLs to a Layer 2 or 3 interface, you can display the access groups on the interface. You can also display the MAC ACLs applied to a Layer 2 interface. You can use the privileged EXEC commands as described in this table to display this information.
Table 2 Commands for Displaying Access Lists and Access GroupsCommand Purpose Displays the contents of one or all current IP and MAC address access lists or a specific access list (numbered or named).
Displays the contents of all current IP access lists or a specific IP access list (numbered or named).
Displays detailed configuration and status of an interface. If IP is enabled on the interface and ACLs have been applied by using the ip access-group interface configuration command, the access groups are included in the display.
Displays the contents of the configuration file for the switch or the specified interface, including all configured MAC and IP access lists and which access groups are applied to an interface.
Displays MAC access lists applied to all Layer 2 interfaces or the specified
You can also monitor VLAN maps by displaying information about VLAN access maps or VLAN filters. Use the privileged EXEC commands in this table to display VLAN map information.
Table 3 Commands for Displaying VLAN Map InformationCommand Purpose Displays information about all VLAN access maps or the specified access map.
Displays information about all VLAN filters or about a specified VLAN or VLAN access map.
Configuration Examples for ACLs
- Examples: Using Time Ranges with ACLs
- Examples: Including Comments in ACLs
- IPv4 ACL Configuration Examples
- Configuration Examples for ACLs and VLAN Maps
- Configuration Examples for Using VLAN Maps in Your Network
- Configuration Examples of Router ACLs and VLAN Maps Applied to VLANs
Examples: Using Time Ranges with ACLs
This example shows how to verify after you configure time ranges for workhours and to configure January 1, 2006, as a company holiday.
Switch# show time-range time-range entry: new_year_day_2003 (inactive) absolute start 00:00 01 January 2006 end 23:59 01 January 2006 time-range entry: workhours (inactive) periodic weekdays 8:00 to 12:00 periodic weekdays 13:00 to 17:00To apply a time range, enter the time-range name in an extended ACL that can implement time ranges. This example shows how to create and verify extended access list 188 that denies TCP traffic from any source to any destination during the defined holiday times and permits all TCP traffic during work hours.
Switch(config)# access-list 188 deny tcp any any time-range new_year_day_2006 Switch(config)# access-list 188 permit tcp any any time-range workhours Switch(config)# end Switch# show access-lists Extended IP access list 188 10 deny tcp any any time-range new_year_day_2006 (inactive) 20 permit tcp any any time-range workhours (inactive)This example uses named ACLs to permit and deny the same traffic.
Switch(config)# ip access-list extended deny_access Switch(config-ext-nacl)# deny tcp any any time-range new_year_day_2006 Switch(config-ext-nacl)# exit Switch(config)# ip access-list extended may_access Switch(config-ext-nacl)# permit tcp any any time-range workhours Switch(config-ext-nacl)# end Switch# show ip access-lists Extended IP access list lpip_default 10 permit ip any any Extended IP access list deny_access 10 deny tcp any any time-range new_year_day_2006 (inactive) Extended IP access list may_access 10 permit tcp any any time-range workhours (inactive)Examples: Including Comments in ACLs
You can use the remark keyword to include comments (remarks) about entries in any IP standard or extended ACL. The remarks make the ACL easier for you to understand and scan. Each remark line is limited to 100 characters.
The remark can go before or after a permit or deny statement. You should be consistent about where you put the remark so that it is clear which remark describes which permit or deny statement. For example, it would be confusing to have some remarks before the associated permit or deny statements and some remarks after the associated statements.
To include a comment for IP numbered standard or extended ACLs, use the access-list access-list number remark remark global configuration command. To remove the remark, use the no form of this command.
In this example, the workstation that belongs to Jones is allowed access, and the workstation that belongs to Smith is not allowed access:
Switch(config)# access-list 1 remark Permit only Jones workstation through Switch(config)# access-list 1 permit 171.69.2.88 Switch(config)# access-list 1 remark Do not allow Smith through Switch(config)# access-list 1 deny 171.69.3.13For an entry in a named IP ACL, use the remark access-list configuration command. To remove the remark, use the no form of this command.
In this example, the Jones subnet is not allowed to use outbound Telnet:
Switch(config)# ip access-list extended telnetting Switch(config-ext-nacl)# remark Do not allow Jones subnet to telnet out Switch(config-ext-nacl)# deny tcp host 171.69.2.88 any eq telnetIPv4 ACL Configuration Examples
This section provides examples of configuring and applying IPv4 ACLs. For detailed information about compiling ACLs, see the Cisco IOS Security Configuration Guide, Release 12.4 and to the Configuring IP Services” section in the “IP Addressing and Services” chapter of the Cisco IOS IP Configuration Guide, Release 12.4.
- ACLs in a Small Networked Office
- Examples: ACLs in a Small Networked Office
- Example: Numbered ACLs
- Examples: Extended ACLs
- Examples: Named ACLs
- Examples: Time Range Applied to an IP ACL
- Examples: Commented IP ACL Entries
- Examples: ACL Logging
ACLs in a Small Networked Office
Figure 3. Using Router ACLs to Control Traffic. This shows a small networked office environment with routed Port 2 connected to Server A, containing benefits and other information that all employees can access, and routed Port 1 connected to Server B, containing confidential payroll data. All users can access Server A, but Server B has restricted access.Use router ACLs to do this in one of two ways:
Examples: ACLs in a Small Networked Office
This example uses a standard ACL to filter traffic coming into Server B from a port, permitting traffic only from Accounting’s source addresses 172.20.128.64 to 172.20.128.95. The ACL is applied to traffic coming out of routed Port 1 from the specified source address.
Switch(config)# access-list 6 permit 172.20.128.64 0.0.0.31 Switch(config)# end Switch# how access-lists Standard IP access list 6 10 permit 172.20.128.64, wildcard bits 0.0.0.31 Switch(config)# interface gigabitethernet1/0/1 Switch(config-if)# ip access-group 6 outThis example uses an extended ACL to filter traffic coming from Server B into a port, permitting traffic from any source address (in this case Server B) to only the Accounting destination addresses 172.20.128.64 to 172.20.128.95. The ACL is applied to traffic going into routed Port 1, permitting it to go only to the specified destination addresses. Note that with extended ACLs, you must enter the protocol (IP) before the source and destination information.
Switch(config)# access-list 106 permit ip any 172.20.128.64 0.0.0.31 Switch(config)# end Switch# show access-lists Extended IP access list 106 10 permit ip any 172.20.128.64 0.0.0.31 Switch(config)# interface gigabitethernet1/0/1 Switch(config-if)# ip access-group 106 inExample: Numbered ACLs
In this example, network 36.0.0.0 is a Class A network whose second octet specifies a subnet; that is, its subnet mask is 255.255.0.0. The third and fourth octets of a network 36.0.0.0 address specify a particular host. Using access list 2, the switch accepts one address on subnet 48 and reject all others on that subnet. The last line of the list shows that the switch accepts addresses on all other network 36.0.0.0 subnets. The ACL is applied to packets entering a port.
Switch(config)# access-list 2 permit 36.48.0.3 Switch(config)# access-list 2 deny 36.48.0.0 0.0.255.255 Switch(config)# access-list 2 permit 36.0.0.0 0.255.255.255 Switch(config)# interface gigabitethernet2/0/1 Switch(config-if)# ip access-group 2 inExamples: Extended ACLs
In this example, the first line permits any incoming TCP connections with destination ports greater than 1023. The second line permits incoming TCP connections to the Simple Mail Transfer Protocol (SMTP) port of host 128.88.1.2. The third line permits incoming ICMP messages for error feedback.
Switch(config)# access-list 102 permit tcp any 128.88.0.0 0.0.255.255 gt 1023 Switch(config)# access-list 102 permit tcp any host 128.88.1.2 eq 25 Switch(config)# access-list 102 permit icmp any any Switch(config)# interface gigabitethernet2/0/1 Switch(config-if)# ip access-group 102 inIn this example, suppose that you have a network connected to the Internet, and you want any host on the network to be able to form TCP connections to any host on the Internet. However, you do not want IP hosts to be able to form TCP connections to hosts on your network, except to the mail (SMTP) port of a dedicated mail host.
SMTP uses TCP port 25 on one end of the connection and a random port number on the other end. The same port numbers are used throughout the life of the connection. Mail packets coming in from the Internet have a destination port of 25. Outbound packets have the port numbers reversed. Because the secure system of the network always accepts mail connections on port 25, the incoming and outgoing services are separately controlled. The ACL must be configured as an input ACL on the outbound interface and an output ACL on the inbound interface.
Switch(config)# access-list 102 permit tcp any 128.88.0.0 0.0.255.255 eq 23 Switch(config)# access-list 102 permit tcp any 128.88.0.0 0.0.255.255 eq 25 Switch(config)# interface gigabitethernet1/0/1 Switch(config-if)# ip access-group 102 inIn this example, the network is a Class B network with the address 128.88.0.0, and the mail host address is 128.88.1.2. The established keyword is used only for the TCP to show an established connection. A match occurs if the TCP datagram has the ACK or RST bits set, which show that the packet belongs to an existing connection. Gigabit Ethernet interface 1 on stack member 1 is the interface that connects the router to the Internet.
Switch(config)# access-list 102 permit tcp any 128.88.0.0 0.0.255.255 established Switch(config)# access-list 102 permit tcp any host 128.88.1.2 eq 25 Switch(config)# interface gigabitethernet1/0/1 Switch(config-if)# ip access-group 102 inExamples: Named ACLs
This example creates a standard ACL named internet_filter and an extended ACL named marketing_group. The internet_filter ACL allows all traffic from the source address 1.2.3.4.
Switch(config)# ip access-list standard Internet_filter Switch(config-ext-nacl)# permit 1.2.3.4 Switch(config-ext-nacl)# exitThe marketing_group ACL allows any TCP Telnet traffic to the destination address and wildcard 171.69.0.0 0.0.255.255 and denies any other TCP traffic. It permits ICMP traffic, denies UDP traffic from any source to the destination address range 171.69.0.0 through 179.69.255.255 with a destination port less than 1024, denies any other IP traffic, and provides a log of the result.
Switch(config)# ip access-list extended marketing_group Switch(config-ext-nacl)# permit tcp any 171.69.0.0 0.0.255.255 eq telnet Switch(config-ext-nacl)# deny tcp any any Switch(config-ext-nacl)# permit icmp any any Switch(config-ext-nacl)# deny udp any 171.69.0.0 0.0.255.255 lt 1024 Switch(config-ext-nacl)# deny ip any any log Switch(config-ext-nacl)# exitThe Internet_filter ACL is applied to outgoing traffic and the marketing_group ACL is applied to incoming traffic on a Layer 3 port.
Switch(config)# interface gigabitethernet3/0/2 Switch(config-if)# no switchport Switch(config-if)# ip address 2.0.5.1 255.255.255.0 Switch(config-if)# ip access-group Internet_filter out Switch(config-if)# ip access-group marketing_group inExamples: Time Range Applied to an IP ACL
This example denies HTTP traffic on IP on Monday through Friday between the hours of 8:00 a.m. and 6:00 p.m (18:00). The example allows UDP traffic only on Saturday and Sunday from noon to 8:00 p.m. (20:00).
Switch(config)# time-range no-http Switch(config)# periodic weekdays 8:00 to 18:00 ! Switch(config)# time-range udp-yes Switch(config)# periodic weekend 12:00 to 20:00 ! Switch(config)# ip access-list extended strict Switch(config-ext-nacl)# deny tcp any any eq www time-range no-http Switch(config-ext-nacl)# permit udp any any time-range udp-yes ! Switch(config-ext-nacl)# exit Switch(config)# interface gigabitethernet2/0/1 Switch(config-if)# ip access-group strict inExamples: Commented IP ACL Entries
In this example of a numbered ACL, the workstation that belongs to Jones is allowed access, and the workstation that belongs to Smith is not allowed access:
Switch(config)# access-list 1 remark Permit only Jones workstation through Switch(config)# access-list 1 permit 171.69.2.88 Switch(config)# access-list 1 remark Do not allow Smith workstation through Switch(config)# access-list 1 deny 171.69.3.13In this example of a numbered ACL, the Winter and Smith workstations are not allowed to browse the web:
Switch(config)# access-list 100 remark Do not allow Winter to browse the web Switch(config)# access-list 100 deny host 171.69.3.85 any eq www Switch(config)# access-list 100 remark Do not allow Smith to browse the web Switch(config)# access-list 100 deny host 171.69.3.13 any eq wwwIn this example of a named ACL, the Jones subnet is not allowed access:
Switch(config)# ip access-list standard prevention Switch(config-std-nacl)# remark Do not allow Jones subnet through Switch(config-std-nacl)# deny 171.69.0.0 0.0.255.255In this example of a named ACL, the Jones subnet is not allowed to use outbound Telnet:
Switch(config)# ip access-list extended telnetting Switch(config-ext-nacl)# remark Do not allow Jones subnet to telnet out Switch(config-ext-nacl)# deny tcp 171.69.0.0 0.0.255.255 any eq telnetExamples: ACL Logging
Two variations of logging are supported on router ACLs. The log keyword sends an informational logging message to the console about the packet that matches the entry; the log-input keyword includes the input interface in the log entry.
In this example, standard named access list stan1 denies traffic from 10.1.1.0 0.0.0.255, allows traffic from all other sources, and includes the log keyword.
Switch(config)# ip access-list standard stan1 Switch(config-std-nacl)# deny 10.1.1.0 0.0.0.255 log Switch(config-std-nacl)# permit any log Switch(config-std-nacl)# exit Switch(config)# interface gigabitethernet1/0/1 Switch(config-if)# ip access-group stan1 in Switch(config-if)# end Switch# show logging Syslog logging: enabled (0 messages dropped, 0 flushes, 0 overruns) Console logging: level debugging, 37 messages logged Monitor logging: level debugging, 0 messages logged Buffer logging: level debugging, 37 messages logged File logging: disabled Trap logging: level debugging, 39 message lines logged Log Buffer (4096 bytes): 00:00:48: NTP: authentication delay calculation problems <output truncated> 00:09:34:%SEC-6-IPACCESSLOGS:list stan1 permitted 0.0.0.0 1 packet 00:09:59:%SEC-6-IPACCESSLOGS:list stan1 denied 10.1.1.15 1 packet 00:10:11:%SEC-6-IPACCESSLOGS:list stan1 permitted 0.0.0.0 1 packetThis example is a named extended access list ext1 that permits ICMP packets from any source to 10.1.1.0 0.0.0.255 and denies all UDP packets.
Switch(config)# ip access-list extended ext1 Switch(config-ext-nacl)# permit icmp any 10.1.1.0 0.0.0.255 log Switch(config-ext-nacl)# deny udp any any log Switch(config-std-nacl)# exit Switch(config)# interface gigabitethernet1/0/2 Switch(config-if)# ip access-group ext1 inThis is a an example of a log for an extended ACL:
01:24:23:%SEC-6-IPACCESSLOGDP:list ext1 permitted icmp 10.1.1.15 -> 10.1.1.61 (0/0), 1 packet 01:25:14:%SEC-6-IPACCESSLOGDP:list ext1 permitted icmp 10.1.1.15 -> 10.1.1.61 (0/0), 7 packets 01:26:12:%SEC-6-IPACCESSLOGP:list ext1 denied udp 0.0.0.0(0) -> 255.255.255.255(0), 1 packet 01:31:33:%SEC-6-IPACCESSLOGP:list ext1 denied udp 0.0.0.0(0) -> 255.255.255.255(0), 8 packetsNote that all logging entries for IP ACLs start with %SEC-6-IPACCESSLOG with minor variations in format depending on the kind of ACL and the access entry that has been matched.
This is an example of an output message when the log-input keyword is entered:
00:04:21:%SEC-6-IPACCESSLOGDP:list inputlog permitted icmp 10.1.1.10 (Vlan1 0001.42ef.a400) -> 10.1.1.61 (0/0), 1 packetA log message for the same sort of packet using the log keyword does not include the input interface information:
00:05:47:%SEC-6-IPACCESSLOGDP:list inputlog permitted icmp 10.1.1.10 -> 10.1.1.61 (0/0), 1 packetConfiguration Examples for ACLs and VLAN Maps
- Example: Creating an ACL and a VLAN Map to Deny a Packet
- Example: Creating an ACL and a VLAN Map to Permit a Packet
- Example: Default Action of Dropping IP Packets and Forwarding MAC Packets
- Example: Default Action of Dropping MAC Packets and Forwarding IP Packets
- Example: Default Action of Dropping All Packets
Example: Creating an ACL and a VLAN Map to Deny a Packet
This example shows how to create an ACL and a VLAN map to deny a packet. In the first map, any packets that match the ip1 ACL (TCP packets) would be dropped. You first create the ip1 ACL to permit any TCP packet and no other packets. Because there is a match clause for IP packets in the VLAN map, the default action is to drop any IP packet that does not match any of the match clauses.
Switch(config)# ip access-list extended ip1 Switch(config-ext-nacl)# permit tcp any any Switch(config-ext-nacl)# exit Switch(config)# vlan access-map map_1 10 Switch(config-access-map)# match ip address ip1 Switch(config-access-map)# action dropExample: Creating an ACL and a VLAN Map to Permit a Packet
This example shows how to create a VLAN map to permit a packet. ACL ip2 permits UDP packets and any packets that match the ip2 ACL are forwarded. In this map, any IP packets that did not match any of the previous ACLs (that is, packets that are not TCP packets or UDP packets) would get dropped.
Switch(config)# ip access-list extended ip2 Switch(config-ext-nacl)# permit udp any any Switch(config-ext-nacl)# exit Switch(config)# vlan access-map map_1 20 Switch(config-access-map)# match ip address ip2 Switch(config-access-map)# action forwardExample: Default Action of Dropping IP Packets and Forwarding MAC Packets
In this example, the VLAN map has a default action of drop for IP packets and a default action of forward for MAC packets. Used with standard ACL 101 and extended named access lists igmp-match and tcp-match, the map will have the following results:
- Forward all UDP packets
- Drop all IGMP packets
- Forward all TCP packets
- Drop all other IP packets
- Forward all non-IP packets
Switch(config)# access-list 101 permit udp any any Switch(config)# ip access-list extended igmp-match Switch(config-ext-nacl)# permit igmp any any Switch(config)# action forward Switch(config-ext-nacl)# permit tcp any any Switch(config-ext-nacl)# exit Switch(config)# vlan access-map drop-ip-default 10 Switch(config-access-map)# match ip address 101 Switch(config-access-map)# action forward Switch(config-access-map)# exit Switch(config)# vlan access-map drop-ip-default 20 Switch(config-access-map)# match ip address igmp-match Switch(config-access-map)# action drop Switch(config-access-map)# exit Switch(config)# vlan access-map drop-ip-default 30 Switch(config-access-map)# match ip address tcp-match Switch(config-access-map)# action forwardExample: Default Action of Dropping MAC Packets and Forwarding IP Packets
In this example, the VLAN map has a default action of drop for MAC packets and a default action of forward for IP packets. Used with MAC extended access lists good-hosts and good-protocols, the map will have the following results:
- Forward MAC packets from hosts 0000.0c00.0111 and 0000.0c00.0211
- Forward MAC packets with decnet-iv or vines-ip protocols
- Drop all other non-IP packets
- Forward all IP packets
Switch(config)# mac access-list extended good-hosts Switch(config-ext-macl)# permit host 000.0c00.0111 any Switch(config-ext-macl)# permit host 000.0c00.0211 any Switch(config-ext-nacl)# exit Switch(config)# action forward Switch(config-ext-macl)# mac access-list extended good-protocols Switch(config-ext-macl)# permit any any vines-ip Switch(config-ext-nacl)# exit Switch(config)# vlan access-map drop-mac-default 10 Switch(config-access-map)# match mac address good-hosts Switch(config-access-map)# action forward Switch(config-access-map)# exit Switch(config)# vlan access-map drop-mac-default 20 Switch(config-access-map)# match mac address good-protocols Switch(config-access-map)# action forwardExample: Default Action of Dropping All Packets
In this example, the VLAN map has a default action of drop for all packets (IP and non-IP). Used with access lists tcp-match and good-hosts from Examples 2 and 3, the map will have the following results:
- Forward all TCP packets
- Forward MAC packets from hosts 0000.0c00.0111 and 0000.0c00.0211
- Drop all other IP packets
- Drop all other MAC packets
Switch(config)# vlan access-map drop-all-default 10 Switch(config-access-map)# match ip address tcp-match Switch(config-access-map)# action forward Switch(config-access-map)# exit Switch(config)# vlan access-map drop-all-default 20 Switch(config-access-map)# match mac address good-hosts Switch(config-access-map)# action forwardConfiguration Examples for Using VLAN Maps in Your Network
- Example: Wiring Closet Configuration
- Example: Restricting Access to a Server on Another VLAN
- Example: Denying Access to a Server on Another VLAN
Example: Wiring Closet Configuration
Figure 4. Wiring Closet Configuration. In a wiring closet configuration, routing might not be enabled on the switch. In this configuration, the switch can still support a VLAN map and a QoS classification ACL. Assume that Host X and Host Y are in different VLANs and are connected to wiring closet switches A and C. Traffic from Host X to Host Y is eventually being routed by Switch B, a Layer 3 switch with routing enabled. Traffic from Host X to Host Y can be access-controlled at the traffic entry point, Switch A.If you do not want HTTP traffic switched from Host X to Host Y, you can configure a VLAN map on Switch A to drop all HTTP traffic from Host X (IP address 10.1.1.32) to Host Y (IP address 10.1.1.34) at Switch A and not bridge it to Switch B.
First, define the IP access list http that permits (matches) any TCP traffic on the HTTP port.
Switch(config)# ip access-list extended http Switch(config-ext-nacl)# permit tcp host 10.1.1.32 host 10.1.1.34 eq www Switch(config-ext-nacl)# exitNext, create VLAN access map map2 so that traffic that matches the http access list is dropped and all other IP traffic is forwarded.
Switch(config)# vlan access-map map2 10 Switch(config-access-map)# match ip address http Switch(config-access-map)# action drop Switch(config-access-map)# exit Switch(config)# ip access-list extended match_all Switch(config-ext-nacl)# permit ip any any Switch(config-ext-nacl)# exit Switch(config)# vlan access-map map2 20 Switch(config-access-map)# match ip address match_all Switch(config-access-map)# action forwardThen, apply VLAN access map map2 to VLAN 1.
Switch(config)# vlan filter map2 vlan 1Example: Restricting Access to a Server on Another VLAN
Example: Denying Access to a Server on Another VLAN
This example shows how to deny access to a server on another VLAN by creating the VLAN map SERVER 1 that denies access to hosts in subnet 10.1.2.0.8, host 10.1.1.4, and host 10.1.1.8 and permits other IP traffic. The final step is to apply the map SERVER1 to VLAN 10.
Define the IP ACL that will match the correct packets.
Switch(config)# ip access-list extended SERVER1_ACL Switch(config-ext-nacl))# permit ip 10.1.2.0 0.0.0.255 host 10.1.1.100 Switch(config-ext-nacl))# permit ip host 10.1.1.4 host 10.1.1.100 Switch(config-ext-nacl))# permit ip host 10.1.1.8 host 10.1.1.100 Switch(config-ext-nacl))# exitDefine a VLAN map using this ACL that will drop IP packets that match SERVER1_ACL and forward IP packets that do not match the ACL.
Switch(config)# vlan access-map SERVER1_MAP Switch(config-access-map)# match ip address SERVER1_ACL Switch(config-access-map)# action drop Switch(config)# vlan access-map SERVER1_MAP 20 Switch(config-access-map)# action forward Switch(config-access-map)# exitApply the VLAN map to VLAN 10.
Switch(config)# vlan filter SERVER1_MAP vlan-list 10Configuration Examples of Router ACLs and VLAN Maps Applied to VLANs
This section gives examples of applying router ACLs and VLAN maps to a VLAN for switched, bridged, routed, and multicast packets. Although the following illustrations show packets being forwarded to their destination, each time the packet’s path crosses a line indicating a VLAN map or an ACL, it is also possible that the packet might be dropped, rather than forwarded.
- Example: ACLs and Switched Packets
- Example: ACLs and Bridged Packets
- Example: ACLs and Routed Packets
- Example: ACLs and Multicast Packets
Example: ACLs and Multicast Packets
Figure 9. Applying ACLs on Multicast Packets.This example shows how ACLs are applied on packets that are replicated for IP multicasting. A multicast packet being routed has two different kinds of filters applied: one for destinations that are other ports in the input VLAN and another for each of the destinations that are in other VLANs to which the packet has been routed. The packet might be routed to more than one output VLAN, in which case a different router output ACL and VLAN map would apply for each destination VLAN. The final result is that the packet might be permitted in some of the output VLANs and not in others. A copy of the packet is forwarded to those destinations where it is permitted. However, if the input VLAN map drops the packet, no destination receives a copy of the packet.
Additional References
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