Access lists determine what traffic is blocked and what traffic is forwarded at router interfaces and allow filtering of traffic based on source and destination addresses, and inbound and outbound traffic to a specific interface. Standard IPv6 ACL functionality was extended to support traffic filtering based on IPv6 option headers and optional, upper-layer protocol type information for finer granularity of control. Standard IPv6 ACL functionality was extended to support traffic filtering based on IPv6 option headers and optional, upper-layer protocol type information for finer granularity of control.
This module describes how to configure IPv6 traffic filtering and to control access to virtual terminal lines.
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. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to
www.cisco.com/go/cfn. An account on Cisco.com is not required.
The standard ACL functionality in IPv6 is similar to standard ACLs in IPv4. Access lists determine what traffic is blocked and what traffic is forwarded at router interfaces and allow filtering based on source and destination addresses, inbound and outbound to a specific interface. Each access list has an implicit deny statement at the end. IPv6 ACLs are defined and their deny and permit conditions are set using the
ipv6access-listcommand with the
deny and
permit keywords in global configuration mode.
IPv6 extended ACLs augments standard IPv6 ACL functionality to support traffic filtering based on IPv6 option headers and optional, upper-layer protocol type information for finer granularity of control (functionality similar to extended ACLs in IPv4).
The following header fields are all used for IPv6 inspection--traffic class, flow label, payload length, next header, hop limit, and source or destination address. For further information on and descriptions of the IPv6 header fields, see RFC 2474.
Access Class Filtering in IPv6
Filtering incoming and outgoing connections to and from the router based on an IPv6 ACL is performed using the ipv6access-class command in line configuration mode. The ipv6access-class command is similar to the access-class command, except the IPv6 ACLs are defined by a name. If the IPv6 ACL is applied to inbound traffic, the source address in the ACL is matched against the incoming connection source address and the destination address in the ACL is matched against the local router address on the interface. If the IPv6 ACL is applied to outbound traffic, the source address in the ACL is matched against the local router address on the interface and the destination address in the ACL is matched against the outgoing connection source address. We recommend that identical restrictions are set on all the virtual terminal lines because a user can attempt to connect to any of them.
Tunneling Support
IPv6 packets tunneled in IPv4 are not inspected. If a tunnel terminates on a router, and IPv6 traffic exiting the tunnel is nonterminating, then the traffic is inspected.
Virtual Fragment Reassembly
When VFR is enabled, VFR processing begins after ACL input lists are checked against incoming packets. The incoming packets are tagged with the appropriate VFR information.
Creating and Configuring an IPv6 ACL for Traffic Filtering
This section describes how to configure your networking devices to filter traffic, function as a firewall, or detect potential viruses.
Before You Begin
Note
Each IPv6 ACL contains implicit permit rules to enable IPv6 neighbor discovery. These rules can be overridden by the user by placing a deny ipv6 any any statement within an ACL. The IPv6 neighbor discovery process makes use of the IPv6 network layer service; therefore, by default, IPv6 ACLs implicitly allow IPv6 neighbor discovery packets to be sent and received on an interface. In IPv4, the Address Resolution Protocol (ARP), which is equivalent to the IPv6 neighbor discovery process, makes use of a separate data link layer protocol; therefore, by default, IPv4 ACLs implicitly allow ARP packets to be sent and received on an interface.
Time-based and reflexive ACLs are not supported for IPv4 or IPv6 on the Cisco 12000 series platform. The
reflect,
timeout, and
time-range keywords of the
permit command in IPv6 are excluded on the Cisco 12000 series.
In this example, the
show ipv6 access-list command is used to verify that IPv6 ACLs are configured correctly:
Router> show ipv6 access-list
IPv6 access list inbound
permit tcp any any eq bgp reflect tcptraffic (8 matches) sequence 10
permit tcp any any eq telnet reflect tcptraffic (15 matches) sequence 20
permit udp any any reflect udptraffic sequence 30
IPv6 access list tcptraffic (reflexive) (per-user)
permit tcp host 2001:DB8:1::32 eq bgp host 2001:DB8:2::32 eq 11000 timeout 300 (time left 243) sequence 1
permit tcp host 2001:DB8:1::32 eq telnet host 2001:DB8:2::32 eq 11001 timeout 300 (time left 296) sequence 2
IPv6 access list outbound
evaluate udptraffic
evaluate tcptraffic
Example: Creating and Applying an IPv6 ACL
This example configures two IPv6 ACLs named OUTBOUND and INBOUND and applies both ACLs to outbound and inbound traffic on Ethernet interface 0. The first and second permit entries in the OUTBOUND list permit all TCP and User Datagram Protocol (UDP) packets from network 2001:DB8:0300:0201::/32 to exit out of Ethernet interface 0. The entries also configure the temporary IPv6 reflexive ACL named REFLECTOUT to filter returning (incoming) TCP and UDP packets on Ethernet interface 0. The first deny entry in the OUTBOUND list keeps all packets from the network fec0:0:0:0201::/64 (packets that have the site-local prefix fec0:0:0:0201 as the first 64 bits of their source IPv6 address) from exiting out of Ethernet interface 0.
The
evaluate command in the INBOUND list applies the temporary IPv6 reflexive ACL named REFLECTOUT to inbound TCP and UDP packets on Ethernet interface 0. When outgoing TCP or UDP packets are permitted on Ethernet interface 0 by the OUTBOUND list, the INBOUND list uses the REFLECTOUT list to match (evaluate) the returning (incoming) TCP and UDP packets.
ipv6 access-list OUTBOUND
permit tcp 2001:DB8:0300:0201::/32 any reflect REFLECTOUT
permit udp 2001:DB8:0300:0201::/32 any reflect REFLECTOUT
deny fec0:0:0:0201::/64 any
ipv6 access-list INBOUND
evaluate REFLECTOUT
interface ethernet 0
ipv6 traffic-filter OUTBOUND out
ipv6 traffic-filter INBOUND in
Note
Given that a
permitanyany statement is not included as the last entry in the OUTBOUND or INBOUND ACL, only TCP and UDP packets matching the configured permit entries in the ACL and ICMP packets matching the implicit permit conditions in the ACL are permitted out of and in to Ethernet interface 0 (the implicit deny all condition at the end of the ACL denies all other packet types on the interface).
The example configures HTTP access to be restricted to certain hours during the day, and to log any activity outside of the permitted hours:
time-range lunchtime
periodic weekdays 12:00 to 13:00
ipv6 access-list OUTBOUND
permit tcp any any eq www time-range lunchtime
deny tcp any any eq www log-input
permit tcp 2001:DB8::/32 any
permit udp 2001:DB8::/32 any
Example Controlling Access to a vty
In the following example, incoming connections to the virtual terminal lines 0 to 4 are filtered based on the IPv6 access list named acl1:
ipv6 access-list acl1
permit ipv6 host 2001:DB8:0:4::2/32 any
!
line vty 0 4
ipv6 access-class acl1 in
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The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to
www.cisco.com/go/cfn. An account on Cisco.com is not required.
Table 1
Feature Information for IPv6 Access Control Lists
Feature Name
Releases
Feature Information
IPv6 Services: Standard Access Control Lists
12.0(22)S
12.2(14)S
12.2(28)SB
12.2(25)SG
12.2(33)SRA
12.2(17a)SX1
12.2(2)T
12.3
12.3(2)T
12.4
12.4(2)T
15.0(1)S
Access lists determine what traffic is blocked and what traffic is forwarded at router interfaces and allow filtering based on source and destination addresses, inbound and outbound to a specific interface.
IPv6 Services: Extended Access Control Lists
12.0(23)S
12.2(14)S
12.2(28)SB
12.2(25)SG
12.2(33)SRA
12.2(17a)SX1
12.2(13)T
12.3
12.3(2)T
12.4
12.4(2)T
15.0(1)S
Standard IPv6 ACL functionality was extended to support traffic filtering based on IPv6 option headers and optional, upper-layer protocol type information for finer granularity of control.
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