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Table Of Contents
Configuring Network Security with ACLs
Handling Fragmented and Unfragmented Traffic
Creating Standard and Extended IPv4 ACLs
Creating a Numbered Standard ACL
Creating a Numbered Extended ACL
Creating Named Standard and Extended ACLs
Applying an IPv4 ACL to a Terminal Line
Applying an IPv4 ACL to an Interface
Hardware and Software Treatment of IP ACLs
IPv4 ACL Configuration Examples
Time Range Applied to an IP ACL
Creating Named MAC Extended ACLs
Applying a MAC ACL to a Layer 2 Interface
VLAN Map Configuration Guidelines
Examples of ACLs and VLAN Maps
Using VLAN Maps in Your Network
Denying Access to a Server on Another VLAN
Using VLAN Maps with Router ACLs
VLAN Maps and Router ACL Configuration Guidelines
Examples of Router ACLs and VLAN Maps Applied to VLANs
Displaying IPv4 ACL Configuration
Configuring Network Security with ACLs
This chapter describes how to configure network security on the Cisco ME 3800X and 3600X switch by using access control lists (ACLs), which are also referred to in commands and tables as access lists. Information in this chapter about IP ACLs is specific to IP Version 4 (IPv4).
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ACLs are not supported on ports configured with Ethernet flow point (EFP) service instances.
For complete syntax and usage information for the commands used in this chapter, see the command reference for this release, see the "Configuring IP Services" section in the IP Application Services Configuration Guide, Cisco IOS Release 15, and the Cisco IOS IP Addressing Services Command Reference.
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Understanding ACLs
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.
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.
An ACL contains an ordered list of access control entries (ACEs). Each ACE specifies permit or deny and a set of conditions the packet must satisfy in order to match the ACE. The meaning of permit or deny depends on the context in which the ACL is used.
The switch supports IPv4 ACLs and Ethernet (MAC) ACLs:
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This switch also supports quality of service (QoS) classification ACLs. For more information, see the "Understanding QoS" section.
These sections contain this conceptual information:
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Supported ACLs
The switch supports three applications of ACLs to filter traffic:
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You can use input port ACLs, router ACLs, and VLAN maps on the same switch. However, a port ACL takes precedence over a router ACL or VLAN map.
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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 and you can apply them only in the inbound direction. You cannot apply an ACL to a port configured with a service instance.
These access lists are supported on Layer 2 interfaces:
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The switch examines ACLs associated with all inbound features configured on a given interface and permits or denies packet forwarding based on how the packet matches the entries in the ACL. In this way, ACLs are used to control access to a network or to part of a network. Figure 31-1 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.
Figure 31-1 Using ACLs to Control Traffic to a Network
When you apply a port ACL to a trunk port, the ACL filters traffic on all VLANs present on the trunk port. You cannot apply a port ACL to a port configured with a service instance.
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.
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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.
One ACL can be used with multiple features for a given interface, and one feature can use multiple ACLs. When a single router ACL is used by multiple features, it is examined multiple times.
The switch supports these access lists for IPv4 traffic:
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As with port ACLs, the switch examines ACLs associated with features configured on a given interface. However, router ACLs are supported in both directions. 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. In Figure 31-1, ACLs applied at the router input allow Host A to access the Human Resources network, but prevent Host B from accessing the same network.
VLAN Maps
VLAN ACLs or VLAN maps can access-control all traffic. You can apply VLAN maps to all packets that are routed into or out of a VLAN or are forwarded within a VLAN in the switch. VLAN maps are used for security packet filtering and 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. Figure 31-2 shows how a VLAN map is applied to prevent a specific type of traffic from Host A in VLAN 10 from being forwarded. You can apply only one VLAN map to a VLAN. The map is applied to all switchports in the VLAN, including ports configured with service instances with a bridge domain equal to the VLAN.
Figure 31-2 Using VLAN Maps to Control Traffic
Handling Fragmented and Unfragmented Traffic
IPv4 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 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 IPv4 packet. When the fragment contains no Layer 4 information and the ACE tests some Layer 4 information, the matching rules are modified:
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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 smtpSwitch(config)# access-list 102 deny tcp any host 10.1.1.2 eq telnetSwitch(config)# access-list 102 permit tcp any host 10.1.1.2Switch(config)# access-list 102 deny tcp any any
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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.
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Configuring IPv4 ACLs
Configuring IP v4ACLs on the switch is the same as configuring IPv4 ACLs on other Cisco switches and routers. The process is briefly described here. For more detailed information on configuring ACLs, see the "Configuring IP Services" section in the IP Application Services Configuration Guide, Cisco IOS Release 15. For detailed information about the commands, see the Cisco IOS IP Addressing Services Command Reference.
The switch does not support these Cisco IOS router ACL-related features:
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These are the steps to use IP ACLs on the switch:
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These sections contain this configuration information:
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Creating 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:
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These sections describe access lists and how to create them:
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IPv4 Access List Numbers
The number you use to denote your IPv4 ACL shows the type of access list that you are creating. Table 31-1 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.
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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.
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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.
Creating a Numbered Standard ACL
Beginning in privileged EXEC mode, follow these steps to create a numbered standard ACL:
Use the no access-list access-list-number global configuration command to delete the entire ACL. You cannot delete individual ACEs from numbered access lists.
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This example shows how to create a standard ACL to deny access to IP host 171.69.198.102, permit access to any others, and display the results.
Switch (config)# access-list 2 deny host 171.69.198.102Switch (config)# access-list 2 permit anySwitch(config)# endSwitch# show access-listsStandard IP access list 210 deny 171.69.198.10220 permit anyThe 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 (see the "Applying an IPv4 ACL to a Terminal Line" section), to interfaces (see the "Applying an IPv4 ACL to an Interface" section), or to VLANs (see the "Configuring VLAN Maps" section).
Creating a Numbered Extended ACL
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.
Some protocols also have specific parameters and keywords that apply to that protocol. These IP protocols are supported (protocol keywords are in parentheses in bold):
Authentication Header Protocol (ahp), Enhanced Interior Gateway Routing Protocol (eigrp), Encapsulation Security Payload (esp), 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), or User Datagram Protocol (udp).
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For more details on the specific keywords for each protocol, see Cisco IOS IP Addressing Services Command Reference.
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If you are creating ACLs to be used for quality of service (QoS) classification, these limitations apply:
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Supported parameters can be grouped into these categories: TCP, UDP, ICMP, IGMP, or other IP.
Beginning in privileged EXEC mode, follow these steps to create an extended ACL:
Step 1
configure terminal
Enter global configuration mode.
Step 2 a
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]Note
Define 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 IP 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.
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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:
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The other keywords are optional and have these meanings:
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access-list access-list-number {deny | permit} protocol any any [precedence precedence] [tos tos] [fragments] [log] [log-input] [time-range time-range-name] [dscp dscp]
In access-list configuration mode, define an extended IP access list using 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.
You can use the any keyword in place of source and destination address and wildcard.
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access-list access-list-number {deny | permit} protocol
host source host destination [precedence precedence] [tos tos] [fragments] [log] [log-input] [time-range time-range-name] [dscp dscp]Define an extended IP access list by using 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.
You can use the host keyword in place of the source and destination wildcard or mask.
Step 2b
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](Optional) Define an extended TCP access list and the access conditions.
Enter tcp for Transmission Control Protocol.
The parameters are the same as those described in Step 2a, 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. To see TCP port names, use the ? or see the "Configuring IP Services" section in the "IP Addressing and Services" chapter of the Cisco IOS IP Configuration Guide, Release 12.2. Use only TCP port numbers or names when filtering TCP.
The other optional keywords have these meanings:
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Step 2c
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](Optional) Define an extended UDP access list and the access conditions.
Enter udp for the User Datagram Protocol.
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 parameters are not valid for UDP.
Step 2d
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](Optional) Define an extended ICMP access list and the access conditions.
Enter icmp for Internet Control Message Protocol.
The ICMP parameters are the same as those described for most IP protocols in Step 2a, with the addition of the ICMP message type and code parameters. These optional keywords have these meanings:
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Step 2e
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](Optional) Define an extended IGMP access list and the access conditions.
Enter igmp for Internet Group Management Protocol.
The IGMP parameters are the same as those described for most IP protocols in Step 2a, with this optional parameter.
igmp-type—To match IGMP message type, enter a number from 0 to 15, or enter the message name (host-query, host-report, pim, or trace).
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Step 3
end
Return to privileged EXEC mode.
Step 4
show access-lists [number | name]
Verify the access list configuration.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
Use the no access-list access-list-number global configuration command to delete the entire access list. You cannot delete individual ACEs from numbered access lists.
This example shows how to create and display an extended access list to deny Telnet access from any host in network 171.69.198.0 to any host in network 172.20.52.0 and to permit any others. (The eq keyword after the destination address means to test for the TCP destination port number equaling Telnet.)
Switch(config)# access-list 102 deny tcp 171.69.198.0 0.0.0.255 172.20.52.0 0.0.0.255 eq telnetSwitch(config)# access-list 102 permit tcp any anySwitch(config)# endSwitch# show access-listsExtended IP access list 10210 deny tcp 171.69.198.0 0.0.0.255 172.20.52.0 0.0.0.255 eq telnet20 permit tcp any anyAfter an ACL is created, any additions (possibly entered from the terminal) are placed at the end of the list. You cannot selectively add or remove access list entries from a numbered access list.
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After creating a numbered extended ACL, you can apply it to terminal lines (see the "Applying an IPv4 ACL to a Terminal Line" section), to interfaces (see the "Applying an IPv4 ACL to an Interface" section), or to VLANs (see the "Configuring VLAN Maps" section).
Resequencing ACEs in an ACL
Sequence numbers for the entries in an access list are automatically generated when you create a new ACL.You can use the ip access-list resequence global configuration command to edit the sequence numbers in an ACL and change the order in which ACEs are applied. For example, if you add a new ACE to an ACL, it is placed at the bottom of the list. By changing the sequence number, you can move the ACE to a different position in the ACL.
For more information about the ip access-list resequence command, see this URL:
http://www.cisco.com/en/US/docs/ios/mcl/allreleasemcl/all_book.html
Creating Named Standard and Extended 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.
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Consider these guidelines and limitations before configuring named ACLs:
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Beginning in privileged EXEC mode, follow these steps to create a standard ACL using names:
To remove a named standard ACL, use the no ip access-list standard name global configuration command.
Beginning in privileged EXEC mode, follow these steps to create an extended ACL using names:
Step 1
configure terminal
Enter global configuration mode.
Step 2
ip access-list extended name
Define an extended IPv4 access list using a name and enter access-list configuration mode.
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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]
In access-list configuration mode, specify the conditions allowed or denied. Use the log keyword to get access list logging messages, including violations.
See the "Creating a Numbered Extended ACL" section for definitions of protocols and other keywords.
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Step 4
end
Return to privileged EXEC mode.
Step 5
show access-lists [number | name]
Show the access list configuration.
Step 6
copy running-config startup-config
(Optional) Save your entries in the configuration file.
To remove a named extended ACL, use the no ip access-list extended name global configuration command.
When you are creating standard 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-listSwitch(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.
After creating a named ACL, you can apply it to interfaces (see the "Applying an IPv4 ACL to an Interface" section) or to VLANs (see the "Configuring VLAN Maps" section).
Using Time Ranges with ACLs
You can selectively apply extended ACLs based on the time of day and 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 in the previous sections, the "Creating Standard and Extended IPv4 ACLs" section, and the "Creating Named Standard and Extended ACLs" section.
These are some of the many possible benefits of using time ranges:
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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 TCAM. 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.)
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Beginning in privileged EXEC mode, follow these steps to configure a time-range parameter for an ACL:
Repeat the steps if you want multiple items in effect at different times. To remove a configured time-range limitation, use the no time-range time-range-name global configuration command.
This example shows how to configure time ranges for workhours and to configure January 1, 2006 as a company holiday and to verify your configuration.
Switch(config)# time-range workhoursSwitch(config-time-range)# periodic weekdays 8:00 to 12:00Switch(config-time-range)# periodic weekdays 13:00 to 17:00Switch(config-time-range)# exitSwitch(config)# time-range new_year_day_2006Switch(config-time-range)# absolute start 00:00 1 Jan 2006 end 23:59 1 Jan 2006Switch(config-time-range)# endSwitch# show time-rangetime-range entry: new_year_day_2003 (inactive)absolute start 00:00 01 January 2006 end 23:59 01 January 2006time-range entry: workhours (inactive)periodic weekdays 8:00 to 12:00periodic 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_2006Switch(config)# access-list 188 permit tcp any any time-range workhoursSwitch(config)# endSwitch# show access-listsExtended IP access list 18810 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_accessSwitch(config-ext-nacl)# deny tcp any any time-range new_year_day_2006Switch(config-ext-nacl)# exitSwitch(config)# ip access-list extended may_accessSwitch(config-ext-nacl)# permit tcp any any time-range workhoursSwitch(config-ext-nacl)# endSwitch# show ip access-listsExtended IP access list deny_access10 deny tcp any any time-range new_year_day_2006 (inactive)Extended IP access list may_access10 permit tcp any any time-range workhours (inactive)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 throughSwitch(config)# access-list 1 permit 171.69.2.88Switch(config)# access-list 1 remark Do not allow Smith throughSwitch(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 telnettingSwitch(config-ext-nacl)# remark Do not allow Jones subnet to telnet outSwitch(config-ext-nacl)# deny tcp host 171.69.2.88 any eq telnetApplying an IPv4 ACL to a Terminal Line
You 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.
For procedures for applying ACLs to interfaces, see the "Applying an IPv4 ACL to an Interface" section. For applying ACLs to VLANs, see the "Configuring VLAN Maps" section.
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:
To remove an ACL from a terminal line, use the no access-class access-list-number {in | out} line configuration command.
Applying an IPv4 ACL to an Interface
This section describes how to apply IPv4 ACLs to network interfaces. You can apply an ACL to either outbound or inbound Layer 3 interfaces. You can apply ACLs only to inbound Layer 2 interfaces. Note these guidelines:
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Beginning in privileged EXEC mode, follow these steps to control access to an interface:
To remove the specified access group, use the no ip access-group {access-list-number | name} {in | out} interface configuration command.
This example shows how to apply access list 2 to a port to filter packets entering the port:
Switch(config)# interface gigabitethernet0/1Router(config-if)# ip access-group 2 in
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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.
Hardware and Software Treatment of IP ACLs
ACL processing is primarily accomplished in hardware, but requires forwarding of some traffic flows to the CPU for software processing. If the hardware reaches its capacity to store ACL configurations, packets are sent to the CPU for forwarding. The forwarding rate for software-forwarded traffic is substantially less than for hardware-forwarded traffic.
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For router ACLs, other factors can cause packets to be sent to the CPU:
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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.
If router ACL configuration cannot be applied in hardware, packets arriving in a VLAN that must be routed are routed in software. If ACLs cause large numbers of packets to be sent to the CPU, the switch performance can be negatively affected.
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 access-lists hardware counters privileged EXEC command to obtain some basic hardware ACL statistics for switched and routed packets.
Router ACLs function as follows:
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Troubleshooting ACLs
If this ACL manager message appears and [chars] is the access-list name,
ACLMGR-2-NOVMR: Cannot generate hardware representation of access list [chars]The switch has insufficient resources to create a hardware representation of the ACL. The resources include hardware memory and label space but not CPU memory. A lack of available logical operation units or specialized hardware resources causes this problem. Logical operation units are needed for a TCP flag match or a test other than eq (ne, gt, lt, or range) on TCP, UDP, or SCTP port numbers.
Use one of these workarounds:
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To determine the specialized hardware resources, enter the show platform layer4 acl map privileged EXEC command. If the switch does not have available resources, the output shows that index 0 to index 15 are not available.
For more information about configuring ACLs with insufficient resources, see CSCsq63926 in the Bug Toolkit.
For example, if you apply this ACL to an interface:
permit tcp source source-wildcard destination destination-wildcard range 5 60permit tcp source source-wildcard destination destination-wildcard range 15 160permit tcp source source-wildcard destination destination-wildcard range 115 1660permit tcp source source-wildcard destination destination-wildcardAnd if this message appears:
ACLMGR-2-NOVMR: Cannot generate hardware representation of access list [chars]The flag-related operators are not available. To avoid this issue,
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permit tcp source source-wildcard destination destination-wildcardpermit tcp source source-wildcard destination destination-wildcard range 5 60permit tcp source source-wildcard destination destination-wildcard range 15 160permit tcp source source-wildcard destination destination-wildcard range 115 1660or
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You can now apply the first ACE in the ACL to the interface. The switch allocates the ACE to available mapping bits in the Opselect index and then allocates flag-related operators to use the same bits in the TCAM.
IPv4 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 15.x and the Configuring IP Services" section in the IP Application Services Configuration Guide, Cisco IOS Release 15.x.
Figure 31-3 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:
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Figure 31-3 Using Router ACLs to Control Traffic
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 0.0.0.31Switch(config)# endSwitch# show access-listsStandard IP access list 610 permit 172.20.128.64, wildcard bits 0.0.0.31Switch(config)# interface gigabitethernet0/1Switch(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 0.0.0.31Switch(config)# endSwitch# show access-listsExtended IP access list 10610 permit ip any 172.20.128.64 0.0.0.31Switch(config)# interface gigabitethernet0/1Switch(config-if)# ip access-group 106 inNumbered 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 36.48.0.3Switch(config)# access-list 2 deny 36.48.0.0 0.0.255.255Switch(config)# access-list 2 permit 36.0.0.0 0.255.255.255Switch(config)# interface gigabitethernet0/1Switch(config-if)# ip access-group 2 inExtended 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 1023Switch(config)# access-list 102 permit tcp any host 128.88.1.2 eq 25Switch(config)# access-list 102 permit icmp any anySwitch(config)# interface gigabitethernet0/1Switch(config-if)# ip access-group 102 inFor another example of using an extended ACL, 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.
In 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 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 establishedSwitch(config)# access-list 102 permit tcp any host 128.88.1.2 eq 25Switch(config)# interface gigabitethernet0/1Switch(config-if)# ip access-group 102 inNamed 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_filterSwitch(config-ext-nacl)# permit 1.2.3.4Switch(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_groupSwitch(config-ext-nacl)# permit tcp any 171.69.0.0 0.0.255.255 eq telnetSwitch(config-ext-nacl)# deny tcp any anySwitch(config-ext-nacl)# permit icmp any anySwitch(config-ext-nacl)# deny udp any 171.69.0.0 0.0.255.255 lt 1024Switch(config-ext-nacl)# deny ip any any logSwitch(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 gigabitethernet0/2Switch(config-if)# no switchportSwitch(config-if)# ip address 2.0.5.1 255.255.255.0Switch(config-if)# ip access-group Internet_filter outSwitch(config-if)# ip access-group marketing_group inTime 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-httpSwitch(config)# periodic weekdays 8:00 to 18:00!Switch(config)# time-range udp-yesSwitch(config)# periodic weekend 12:00 to 20:00!Switch(config)# ip access-list extended strictSwitch(config-ext-nacl)# deny tcp any any eq www time-range no-httpSwitch(config-ext-nacl)# permit udp any any time-range udp-yes!Switch(config-ext-nacl)# exitSwitch(config)# interface gigabitethernet0/1Switch(config-if)# ip access-group strict inCommented 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 throughSwitch(config)# access-list 1 permit 171.69.2.88Switch(config)# access-list 1 remark Do not allow Smith workstation throughSwitch(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 webSwitch(config)# access-list 100 deny host 171.69.3.85 any eq wwwSwitch(config)# access-list 100 remark Do not allow Smith to browse the webSwitch(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 preventionSwitch(config-std-nacl)# remark Do not allow Jones subnet throughSwitch(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 telnettingSwitch(config-ext-nacl)# remark Do not allow Jones subnet to telnet outSwitch(config-ext-nacl)# deny tcp 171.69.0.0 0.0.255.255 any eq telnetACL 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 stan1Switch(config-std-nacl)# deny 10.1.1.0 0.0.0.255 logSwitch(config-std-nacl)# permit any logSwitch(config-std-nacl)# exitSwitch(config)# interface gigabitethernet0/1Switch(config-if)# ip access-group stan1 inSwitch(config-if)# endSwitch# show loggingSyslog logging: enabled (0 messages dropped, 0 flushes, 0 overruns)Console logging: level debugging, 37 messages loggedMonitor logging: level debugging, 0 messages loggedBuffer logging: level debugging, 37 messages loggedFile logging: disabledTrap logging: level debugging, 39 message lines loggedLog 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 packet00:09:59:%SEC-6-IPACCESSLOGS:list stan1 denied 10.1.1.15 1 packet00:10:11:%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 ext1Switch(config-ext-nacl)# permit icmp any 10.1.1.0 0.0.0.255 logSwitch(config-ext-nacl)# deny udp any any logSwitch(config-std-nacl)# exitSwitch(config)# interface gigabitethernet0/2Switch(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 packet01:25:14:%SEC-6-IPACCESSLOGDP:list ext1 permitted icmp 10.1.1.15 -> 10.1.1.61 (0/0), 7 packets01:26:12:%SEC-6-IPACCESSLOGP:list ext1 denied udp 0.0.0.0(0) -> 255.255.255.255(0), 1 packet01:31:33:%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 packetCreating Named MAC Extended ACLs
You 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.
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For more information about the supported non-IP protocols in the mac access-list extended command, see the command reference for this release.
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Beginning in privileged EXEC mode, follow these steps to create a named MAC extended ACL:
Use the no mac access-list extended name global configuration command to delete the entire ACL. You can also delete individual ACEs from named MAC extended ACLs.
This example shows how to create and display an access list named mac1, denying only EtherType DECnet Phase IV traffic, but permitting all other types of traffic.
Switch(config)# mac access-list extended mac1Switch(config-ext-macl)# deny any any decnet-ivSwitch(config-ext-macl)# permit any anySwitch(config-ext-macl)# endSwitch # show access-listsExtended MAC access list mac110 deny any any decnet-iv20 permit any anyApplying a MAC ACL to 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:
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Beginning in privileged EXEC mode, follow these steps to apply a MAC access list to control access to a Layer 2 interface:
To remove the specified access group, use the no mac access-group {name} interface configuration command.
This example shows how to apply MAC access list mac1 to a port to filter packets entering the port:
Switch(config)# interface gigabitethernet0/2Router(config-if)# mac access-group mac1 in
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After 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.
Configuring VLAN Maps
This section describes how to configure VLAN maps, which is 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.
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To create a VLAN map and apply it to one or more VLANs, perform these steps:
Step 1
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These sections contain this configuration information:
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VLAN Map Configuration Guidelines
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Creating a VLAN Map
Each 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:
Use the no vlan access-map name global configuration command to delete a map.
Use the no vlan access-map name number global configuration command to delete a single sequence entry from within the map.
Use the no action access-map configuration command to enforce the default action, which is to forward.
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.
Examples of ACLs and VLAN Maps
These examples show how to create ACLs and VLAN maps that for specific purposes.
Example 1
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 ip1ACL 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 ip1Switch(config-ext-nacl)# permit tcp any anySwitch(config-ext-nacl)# exitSwitch(config)# vlan access-map map_1 10Switch(config-access-map)# match ip address ip1Switch(config-access-map)# action dropThis 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 ip2Switch(config-ext-nacl)# permit udp any anySwitch(config-ext-nacl)# exitSwitch(config)# vlan access-map map_1 20Switch(config-access-map)# match ip address ip2Switch(config-access-map)# action forwardExample 2
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:
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Switch(config)# access-list 101 permit udp any anySwitch(config)# ip access-list extended igmp-matchSwitch(config-ext-nacl)# permit igmp any anySwitch(config)# ip access-list extended tcp-matchSwitch(config-ext-nacl)# permit tcp any anySwitch(config-ext-nacl)# exitSwitch(config)# vlan access-map drop-ip-default 10Switch(config-access-map)# match ip address 101Switch(config-access-map)# action forwardSwitch(config-access-map)# exitSwitch(config)# vlan access-map drop-ip-default 20Switch(config-access-map)# match ip address igmp-matchSwitch(config-access-map)# action dropSwitch(config-access-map)# exitSwitch(config)# vlan access-map drop-ip-default 30Switch(config-access-map)# match ip address tcp-matchSwitch(config-access-map)# action forwardExample 3
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:
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Switch(config)# mac access-list extended good-hostsSwitch(config-ext-macl)# permit host 000.0c00.0111 anySwitch(config-ext-macl)# permit host 000.0c00.0211 anySwitch(config-ext-nacl)# exitSwitch(config)# mac access-list extended good-protocolsSwitch(config-ext-macl)# permit any any decnet-ipSwitch(config-ext-macl)# permit any any vines-ipSwitch(config-ext-nacl)# exitSwitch(config)# vlan access-map drop-mac-default 10Switch(config-access-map)# match mac address good-hostsSwitch(config-access-map)# action forwardSwitch(config-access-map)# exitSwitch(config)# vlan access-map drop-mac-default 20Switch(config-access-map)# match mac address good-protocolsSwitch(config-access-map)# action forwardExample 4
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:
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Switch(config)# vlan access-map drop-all-default 10Switch(config-access-map)# match ip address tcp-matchSwitch(config-access-map)# action forwardSwitch(config-access-map)# exitSwitch(config)# vlan access-map drop-all-default 20Switch(config-access-map)# match mac address good-hostsSwitch(config-access-map)# action forwardApplying a VLAN Map to a VLAN
Beginning in privileged EXEC mode, follow these steps to apply a VLAN map to one or more VLANs:
To remove the VLAN map, use the no vlan filter mapname vlan-list list global configuration command.
This example shows how to apply VLAN map 1 to VLANs 20 through 22:
Switch(config)# vlan filter map 1 vlan-list 20-22Using VLAN Maps in Your Network
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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. In Figure 31-4, 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.
Figure 31-4 Wiring Closet Configuration
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 forward 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 httpSwitch(config-ext-nacl)# permit tcp host 10.1.1.32 host 10.1.1.34 eq wwwSwitch(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 10Switch(config-access-map)# match ip address httpSwitch(config-access-map)# action dropSwitch(config-access-map)# exitSwitch(config)# ip access-list extended match_allSwitch(config-ext-nacl)# permit ip any anySwitch(config-ext-nacl)# exitSwitch(config)# vlan access-map map2 20Switch(config-access-map)# match ip address match_allSwitch(config-access-map)# action forwardThen, apply VLAN access map map2 to VLAN 1.
Switch(config)# vlan filter map2 vlan 1Denying Access to a Server on Another VLAN
You can restrict access to a server on another VLAN. For example, server 10.1.1.100 in VLAN 10 needs to have access denied to these hosts (see Figure 31-5):
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Figure 31-5 Deny 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.
Step 1
Switch(config)# ip access-list extended SERVER1_ACLSwitch(config-ext-nacl))# permit ip 10.1.2.0 0.0.0.255 host 10.1.1.100Switch(config-ext-nacl))# permit ip host 10.1.1.4 host 10.1.1.100Switch(config-ext-nacl))# permit ip host 10.1.1.8 host 10.1.1.100Switch(config-ext-nacl))# exitStep 2
Switch(config)# vlan access-map SERVER1_MAPSwitch(config-access-map)# match ip address SERVER1_ACLSwitch(config-access-map)# action dropSwitch(config)# vlan access-map SERVER1_MAP 20Switch(config-access-map)# action forwardSwitch(config-access-map)# exitStep 3
Switch(config)# vlan filter SERVER1_MAP vlan-list 10.
Using VLAN Maps with Router ACLs
To access control 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. If a packet flow matches a VLAN-map deny clause in the ACL, regardless of the router ACL configuration, the packet flow is denied.
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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.
These sections contain information about using VLAN maps with router ACLs:
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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.
The switch hardware provides one lookup for security ACLs for each direction (input and output); therefore, you must merge a router ACL and a VLAN map when they are configured on the same VLAN. Merging the router ACL with the VLAN map might significantly increase the number of ACEs.
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:
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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.
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, 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.
ACLs and Switched Packets
Figure 31-6 shows how an ACL is applied on packets that are switched within a VLAN. Packets switched within the VLAN without being routed or forwarded are only subject to the VLAN map of the input VLAN.
Figure 31-6 Applying ACLs on Switched Packets
ACLs and Routed Packets
Figure 31-7 shows how ACLs are applied on routed packets. For routed packets, the ACLs are applied in this order:
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Figure 31-7 Applying ACLs on Routed Packets
ACLs and Multicast Packets
Figure 31-8 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 (VLAN 10 map in Figure 31-8) drops the packet, no destination receives a copy of the packet.
Figure 31-8 Applying ACLs on Multicast Packets
Displaying IPv4 ACL Configuration
You can display the ACLs that are configured on the switch, and you can display 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 Table 31-2 to display this information.
You can also display information about VLAN access maps or VLAN filters. Use the privileged EXEC commands in Table 31-3 to display VLAN map information.
