Completing Interface Configuration (Routed Mode)

This chapter includes tasks to complete the interface configuration for all models in routed firewall mode. This chapter includes the following sections:

note.gif

Noteblank.gif For multiple context mode, complete the tasks in this section in the context execution space. Enter the changeto context name command to change to the context you want to configure.

Information About Completing Interface Configuration in Routed Mode

This section includes the following topics:

Security Levels

Each interface must have a security level from 0 (lowest) to 100 (highest). For example, you should assign your most secure network, such as the inside host network, to level 100. While the outside network connected to the Internet can be level 0. Other networks, such as DMZs can be in between. You can assign interfaces to the same security level. See the “Allowing Same Security Level Communication” section for more information.

The level controls the following behavior:

  • Network access—By default, there is an implicit permit from a higher security interface to a lower security interface (outbound). Hosts on the higher security interface can access any host on a lower security interface. You can limit access by applying an access list to the interface.

If you enable communication for same security interfaces (see the “Allowing Same Security Level Communication” section), there is an implicit permit for interfaces to access other interfaces on the same security level or lower.

  • Inspection engines—Some application inspection engines are dependent on the security level. For same security interfaces, inspection engines apply to traffic in either direction.

–blank.gif NetBIOS inspection engine—Applied only for outbound connections.

–blank.gif SQL*Net inspection engine—If a control connection for the SQL*Net (formerly OraServ) port exists between a pair of hosts, then only an inbound data connection is permitted through the ASA.

  • Filtering—HTTP(S) and FTP filtering applies only for outbound connections (from a higher level to a lower level).

If you enable communication for same security interfaces, you can filter traffic in either direction.

  • established command—This command allows return connections from a lower security host to a higher security host if there is already an established connection from the higher level host to the lower level host.

If you enable communication for same security interfaces, you can configure established commands for both directions.

Dual IP Stack (IPv4 and IPv6)

The ASA supports the configuration of both IPv6 and IPv4 on an interface. You do not need to enter any special commands to do so; simply enter the IPv4 configuration commands and IPv6 configuration commands as you normally would. Make sure you configure a default route for both IPv4 and IPv6.

Licensing Requirements for Completing Interface Configuration in Routed Mode

 

Model
License Requirement

ASA 5505

VLANs:

Routed Mode:

Base License: 3 (2 regular zones and 1 restricted zone that can only communicate with 1 other zone)

Security Plus License: 20

Transparent Mode:

Base License: 2 active VLANs in 1 bridge group.

Security Plus License: 3 active VLANs: 2 active VLANs in 1 bridge group, and 1 active VLAN for the failover link.

VLAN Trunks:

Base License: None.

Security Plus License: 8.

 

Model
License Requirement

ASA 5510

VLANs1:

Base License: 50

Security Plus License: 100

Interface Speed:

Base License—All interfaces Fast Ethernet.

Security Plus License—Ethernet 0/0 and 0/1: Gigabit Ethernet; all others Fast Ethernet.

Interfaces of all types2:

Base License: 364

Security Plus License: 564

ASA 5520

VLANs 1 :

Base License: 150.

Interfaces of all types 2 :

Base License: 764

ASA 5540

VLANs 1 :

Base License: 200

Interfaces of all types 2 :

Base License: 964

ASA 5550

VLANs 1 :

Base License: 400

Interfaces of all types 2 :

Base License: 1764

ASA 5580

VLANs 1 :

Base License: 1024

Interfaces of all types 2 :

Base License: 4612

ASA 5512-X

VLANs 1 :

Base License: 50

Security Plus License: 100

Interfaces of all types 2 :

Base License: 716

Security Plus License: 916

ASA 5515-X

VLANs 1 :

Base License: 100

Interfaces of all types 2 :

Base License: 916

ASA 5525-X

VLANs 1 :

Base License: 200

Interfaces of all types 2 :

Base License: 1316

ASA 5545-X

VLANs 1 :

Base License: 300

Interfaces of all types 2 :

Base License: 1716

ASA 5555-X

VLANs 1 :

Base License: 500

Interfaces of all types 2 :

Base License: 2516

ASA 5585-X

VLANs 1 :

Base and Security Plus License: 1024

Interface Speed for SSP-10 and SSP-20:

Base License—1-Gigabit Ethernet for fiber interfaces

10 GE I/O License (Security Plus)—10-Gigabit Ethernet for fiber interfaces

(SSP-40 and SSP-60 support 10-Gigabit Ethernet by default.)

Interfaces of all types 2 :

Base and Security Plus License: 4612

1.For an interface to count against the VLAN limit, you must assign a VLAN to it. For example:
interface gigabitethernet 0/0.100
vlan 100

2.The maximum number of combined interfaces; for example, VLANs, physical, redundant, bridge group, and EtherChannel interfaces. Every interface command defined in the configuration counts against this limit. For example, both of the following interfaces count even if the GigabitEthernet 0/0 interface is defined as part of port-channel 1:
interface gigabitethernet 0/0
and
interface port-channel 1

 

Guidelines and Limitations

This section includes the guidelines and limitations for this feature.

Context Mode Guidelines

The ASA 5505 does not support multiple context mode.

  • In multiple context mode, you can only configure context interfaces that you already assigned to the context in the system configuration according to the “Configuring Multiple Contexts” section.
  • PPPoE is not supported in multiple context mode.

Firewall Mode Guidelines

Supported in routed firewall mode. For transparent mode, see Chapter9, “Completing Interface Configuration (Transparent Mode)”

Failover Guidelines

Do not finish configuring failover interfaces with the procedures in this chapter. See the “Configuring Active/Standby Failover” section or the “Configuring Active/Active Failover” section to configure the failover and state links. In multiple context mode, failover interfaces are configured in the system configuration.

IPv6 Guidelines

Supports IPv6.

Default Settings

This section lists default settings for interfaces if you do not have a factory default configuration. For information about the factory default configurations, see the “Factory Default Configurations” section.

Default Security Level

The default security level is 0. If you name an interface “inside” and you do not set the security level explicitly, then the ASA sets the security level to 100.

note.gif

Noteblank.gif If you change the security level of an interface, and you do not want to wait for existing connections to time out before the new security information is used, you can clear the connections using the clear local-host command.

Completing Interface Configuration in Routed Mode

This section includes the following topics:

Task Flow for Completing Interface Configuration

Step 1blank.gif Set up your interfaces depending on your model:

Step 2blank.gif (Multiple context mode) Allocate interfaces to the context according to the “Configuring Multiple Contexts” section.

Step 3blank.gif (Multiple context mode) Enter the changeto context name command to change to the context you want to configure. Configure general interface parameters, including the interface name, security level, and IPv4 address. See the “Configuring General Interface Parameters” section.

Step 4blank.gif (Optional) Configure the MAC address and the MTU. See the “Configuring the MAC Address and MTU” section.

Step 5blank.gif (Optional) Configure IPv6 addressing. See the “Configuring IPv6 Addressing” section.

Step 6blank.gif (Optional) Allow same security level communication, either by allowing communication between two interfaces or by allowing traffic to enter and exit the same interface. See the “Allowing Same Security Level Communication” section.

 

Configuring General Interface Parameters

This procedure describes how to set the name, security level, IPv4 address and other options.

For the ASA 5510 and higher, you must configure interface parameters for the following interface types:

  • Physical interfaces
  • VLAN subinterfaces
  • Redundant interfaces
  • EtherChannel interfaces

For the ASA 5505, you must configure interface parameters for the following interface types:

  • VLAN interfaces

Guidelines and Limitations

  • For the ASA 5550, for maximum throughput, be sure to balance your traffic over the two interface slots; for example, assign the inside interface to slot 1 and the outside interface to slot 0.
  • If you are using failover, do not use this procedure to name interfaces that you are reserving for failover and Stateful Failover communications. See the “Configuring Active/Standby Failover” section or the “Configuring Active/Active Failover” section to configure the failover and state links.

Restrictions

  • PPPoE is not supported in multiple context mode.

Prerequisites

  • Set up your interfaces depending on your model:

–blank.gif ASA 5510 and higher—Chapter12, “Starting Interface Configuration (ASA 5510 and Higher)”

–blank.gif ASA 5505—Chapter13, “Starting Interface Configuration (ASA 5505)”

  • In multiple context mode, you can only configure context interfaces that you already assigned to the context in the system configuration according to the “Configuring Multiple Contexts” section.
  • In multiple context mode, complete this procedure in the context execution space. To change from the system to a context configuration, enter the changeto context name command.

Detailed Steps

 

Command
Purpose

Step 1

For the ASA 5510 and higher:

interface {{ redundant number | port-channel number | physical_interface }[. subinterface ] | mapped_name }

 

For the ASA 5505:

hostname(config)# interface vlan number

 

hostname(config)# interface gigabithethernet 0/0

If you are not already in interface configuration mode, enters interface configuration mode.

The redundant number argument is the redundant interface ID, such as redundant 1.

The port-channel number argument is the EtherChannel interface ID, such as port-channel 1.

See the “Enabling the Physical Interface and Configuring Ethernet Parameters” section for a description of the physical interface ID.

Append the subinterface ID to the physical or redundant interface ID separated by a period (.).

In multiple context mode, enter the mapped_name if one was assigned using the allocate-interface command.

Step 2

nameif name

 

hostname(config-if)# nameif inside

Names the interface.

The name is a text string up to 48 characters, and is not case-sensitive. You can change the name by reentering this command with a new value. Do not enter the no form, because that command causes all commands that refer to that name to be deleted.

Step 3

Do one of the following:

 

ip address ip_address [ mask ] [ standby ip_address ]

 

hostname(config-if)# ip address 10.1.1.1 255.255.255.0 standby 10.1.1.2

Sets the IP address manually.

Note For use with failover, you must set the IP address and standby address manually; DHCP and PPPoE are not supported.

The ip_address and mask arguments set the interface IP address and subnet mask.

The standby ip_address argument is used for failover. See the “Configuring Active/Standby Failover” section or the “Configuring Active/Active Failover” section for more information.

 

ip address dhcp [ setroute ]

 

hostname(config-if)# ip address dhcp

Obtains an IP address from a DHCP server.

The setroute keyword lets the ASA use the default route supplied by the DHCP server.

Reenter this command to reset the DHCP lease and request a new lease.

If you do not enable the interface using the no shutdown command before you enter the ip address dhcp command, some DHCP requests might not be sent.

 

To obtain an IP address from a PPPoE server, see Chapter72, “Configuring the PPPoE Client”

PPPoE is not supported in multiple context mode.

Step 4

security-level number

 

hostname(config-if)# security-level 50

Sets the security level, where number is an integer between 0 (lowest) and 100 (highest). See the “Security Levels” section.

Step 5

(Optional)

management-only

 

hostname(config-if)# management-only

Sets an interface to management-only mode so that it does not pass through traffic.

By default, Management interfaces are configured as management-only. To disable this setting, enter the no management-only command.

(ASA 5512-X through ASA 5555-X) You cannot disable management-only on the Management 0/0 interface.

The management-only command is not supported for a redundant interface.

Example

The following example configures parameters for VLAN 101:

hostname(config)# interface vlan 101
hostname(config-if)# nameif inside
hostname(config-if)# security-level 100
hostname(config-if)# ip address 10.1.1.1 255.255.255.0
 

The following example configures parameters in multiple context mode for the context configuration. The interface ID is a mapped name.

hostname/contextA(config)# interface int1
hostname/contextA(config-if)# nameif outside
hostname/contextA(config-if)# security-level 100
hostname/contextA(config-if)# ip address 10.1.2.1 255.255.255.0

What to Do Next

Configuring the MAC Address and MTU

This section describes how to configure MAC addresses for interfaces and how to set the MTU.

Information About MAC Addresses

By default, the physical interface uses the burned-in MAC address, and all subinterfaces of a physical interface use the same burned-in MAC address.

A redundant interface uses the MAC address of the first physical interface that you add. If you change the order of the member interfaces in the configuration, then the MAC address changes to match the MAC address of the interface that is now listed first. If you assign a MAC address to the redundant interface using this command, then it is used regardless of the member interface MAC addresses.

For an EtherChannel, all interfaces that are part of the channel group share the same MAC address. This feature makes the EtherChannel transparent to network applications and users, because they only see the one logical connection; they have no knowledge of the individual links. The port-channel interface uses the lowest numbered channel group interface MAC address as the port-channel MAC address. Alternatively you can manually configure a MAC address for the port-channel interface. In multiple context mode, you can automatically assign unique MAC addresses to interfaces, including an EtherChannel port interface. We recommend manually, or in multiple context mode, automatically configuring a unique MAC address in case the group channel interface membership changes. If you remove the interface that was providing the port-channel MAC address, then the port-channel MAC address changes to the next lowest numbered interface, thus causing traffic disruption.

In multiple context mode, if you share an interface between contexts, you can assign a unique MAC address to the interface in each context. This feature lets the ASA easily classify packets into the appropriate context. Using a shared interface without unique MAC addresses is possible, but has some limitations. See the “How the ASA Classifies Packets” section for more information. You can assign each MAC address manually, or you can automatically generate MAC addresses for shared interfaces in contexts. See the “Automatically Assigning MAC Addresses to Context Interfaces” section to automatically generate MAC addresses. If you automatically generate MAC addresses, you can use this procedure to override the generated address.

For single context mode, or for interfaces that are not shared in multiple context mode, you might want to assign unique MAC addresses to subinterfaces. For example, your service provider might perform access control based on the MAC address.

Information About the MTU

The MTU is the maximum datagram size that is sent on a connection. Data that is larger than the MTU value is fragmented before being sent.

The ASA supports IP path MTU discovery (as defined in RFC 1191), which allows a host to dynamically discover and cope with the differences in the maximum allowable MTU size of the various links along the path. Sometimes, the ASA cannot forward a datagram because the packet is larger than the MTU that you set for the interface, but the “don't fragment” (DF) bit is set. The network software sends a message to the sending host, alerting it to the problem. The host has to fragment packets for the destination so that they fit the smallest packet size of all the links along the path.

The default MTU is 1500 bytes in a block for Ethernet interfaces. This value is sufficient for most applications, but you can pick a lower number if network conditions require it.

To enable jumbo frames, see the “Enabling Jumbo Frame Support (Supported Models)” section. A jumbo frame is an Ethernet packet larger than the standard maximum of 1518 bytes (including Layer 2 header and FCS), up to 9216 bytes. Jumbo frames require extra memory to process, and assigning more memory for jumbo frames might limit the maximum use of other features, such as access lists. To use jumbo frames, set the value higher, for example, to 9000 bytes.

Prerequisites

  • Set up your interfaces depending on your model:

–blank.gif ASA 5510 and higher—Chapter12, “Starting Interface Configuration (ASA 5510 and Higher)”

–blank.gif ASA 5505—Chapter13, “Starting Interface Configuration (ASA 5505)”

  • In multiple context mode, you can only configure context interfaces that you already assigned to the context in the system configuration according to the “Configuring Multiple Contexts” section.
  • In multiple context mode, complete this procedure in the context execution space. To change from the system to a context configuration, enter the changeto context name command.

Detailed Steps

 

Command
Purpose

Step 1

For the ASA 5510 and higher:

interface {{ redundant number | port-channel number | physical_interface }[. subinterface ] | mapped_name }

 

For the ASA 5505:

hostname(config)# interface vlan number

 

hostname(config)# interface vlan 100

If you are not already in interface configuration mode, enters interface configuration mode.

The redundant number argument is the redundant interface ID, such as redundant 1.

The port-channel number argument is the EtherChannel interface ID, such as port-channel 1.

See the “Enabling the Physical Interface and Configuring Ethernet Parameters” section for a description of the physical interface ID.

Append the subinterface ID to the physical or redundant interface ID separated by a period (.).

In multiple context mode, enter the mapped_name if one was assigned using the allocate-interface command.

Step 2

mac-address m ac_address [ standby mac_address ]

 

hostname(config-if)# mac-address 000C.F142.4CDE

Assigns a private MAC address to this interface. The mac_address is in H.H.H format, where H is a 16-bit hexadecimal digit. For example, the MAC address 00-0C-F1-42-4C-DE is entered as 000C.F142.4CDE.

The first two bytes of a manual MAC address cannot be A2 if you also want to use auto-generated MAC addresses.

For use with failover, set the standby MAC address. If the active unit fails over and the standby unit becomes active, the new active unit starts using the active MAC addresses to minimize network disruption, while the old active unit uses the standby address.

Step 3

mtu interface_name bytes

 

hostname(config)# mtu inside 9200

Sets the MTU between 300 and 65,535 bytes. The default is 1500 bytes.

Note When you set the MTU for a redundant or port-channel interface, the ASA applies the setting to all member interfaces.

For models that support jumbo frames, if you enter a value for any interface that is greater than 1500, then you need to enable jumbo frame support. See the “Enabling Jumbo Frame Support (Supported Models)” section.

What to Do Next

(Optional) Configure IPv6 addressing. See the “Configuring IPv6 Addressing” section.

Configuring IPv6 Addressing

This section describes how to configure IPv6 addressing. For more information about IPv6, see the “Information About IPv6 Support” section and the “IPv6 Addresses” section.

This section includes the following topics:

Information About IPv6

This section includes information about how to configure IPv6, and includes the following topics:

IPv6 Addressing

You can configure two types of unicast addresses for IPv6:

  • Global—The global address is a public address that you can use on the public network.
  • Link-local—The link-local address is a private address that you can only use on the directly-connected network. Routers do not forward packets using link-local addresses; they are only for communication on a particular physical network segment. They can be used for address configuration or for the ND functions such as address resolution and neighbor discovery.

At a minimum, you need to configure a link-local addresses for IPv6 to operate. If you configure a global address, a link-local address is automatically configured on the interface, so you do not also need to specifically configure a link-local address. If you do not configure a global address, then you need to configure the link-local address, either automatically or manually.

note.gif

Noteblank.gif If you want to only configure the link-local addresses, see the ipv6 enable (to auto-configure) or ipv6 address link-local (to manually configure) command in the command reference.

Duplicate Address Detection

During the stateless autoconfiguration process, duplicate address detection (DAD) verifies the uniqueness of new unicast IPv6 addresses before the addresses are assigned to interfaces (the new addresses remain in a tentative state while duplicate address detection is performed). Duplicate address detection is performed first on the new link-local address. When the link-local address is verified as unique, then duplicate address detection is performed all the other IPv6 unicast addresses on the interface.

Duplicate address detection is suspended on interfaces that are administratively down. While an interface is administratively down, the unicast IPv6 addresses assigned to the interface are set to a pending state. An interface returning to an administratively up state restarts duplicate address detection for all of the unicast IPv6 addresses on the interface.

When a duplicate address is identified, the state of the address is set to DUPLICATE, the address is not used, and the following error message is generated:

%ASA-4-325002: Duplicate address ipv6_address/MAC_address on interface
 

If the duplicate address is the link-local address of the interface, the processing of IPv6 packets is disabled on the interface. If the duplicate address is a global address, the address is not used. However, all configuration commands associated with the duplicate address remain as configured while the state of the address is set to DUPLICATE.

If the link-local address for an interface changes, duplicate address detection is performed on the new link-local address and all of the other IPv6 address associated with the interface are regenerated (duplicate address detection is performed only on the new link-local address).

The ASA uses neighbor solicitation messages to perform duplicate address detection. By default, the number of times an interface performs duplicate address detection is 1.

Modified EUI-64 Interface IDs

RFC 3513: Internet Protocol Version 6 (IPv6) Addressing Architecture requires that the interface identifier portion of all unicast IPv6 addresses, except those that start with binary value 000, be 64 bits long and be constructed in Modified EUI-64 format. The ASA can enforce this requirement for hosts attached to the local link.

When this feature is enabled on an interface, the source addresses of IPv6 packets received on that interface are verified against the source MAC addresses to ensure that the interface identifiers use the Modified EUI-64 format. If the IPv6 packets do not use the Modified EUI-64 format for the interface identifier, the packets are dropped and the following system log message is generated:

%ASA-3-325003: EUI-64 source address check failed.
 

The address format verification is only performed when a flow is created. Packets from an existing flow are not checked. Additionally, the address verification can only be performed for hosts on the local link. Packets received from hosts behind a router will fail the address format verification, and be dropped, because their source MAC address will be the router MAC address and not the host MAC address.

Configuring a Global IPv6 Address and Other Options

To configure a global IPv6 address and other options, perform the following steps.

note.gif

Noteblank.gif Configuring the global address automatically configures the link-local address, so you do not need to configure it separately.

Restrictions

The ASA does not support IPv6 anycast addresses.

Prerequisites

  • Set up your interfaces depending on your model:

–blank.gif ASA 5510 and higher—Chapter12, “Starting Interface Configuration (ASA 5510 and Higher)”

–blank.gif ASA 5505—Chapter13, “Starting Interface Configuration (ASA 5505)”

  • In multiple context mode, you can only configure context interfaces that you already assigned to the context in the system configuration according to the “Configuring Multiple Contexts” section.
  • In multiple context mode, complete this procedure in the context execution space. To change from the system to a context configuration, enter the changeto context name command.

Detailed Steps

 

Command
Purpose

Step 1

For the ASA 5510 and higher:

interface {{ redundant number | port-channel number | physical_interface }[. subinterface ] | mapped_name }

 

For the ASA 5505:

hostname(config)# interface vlan number

 

hostname(config)# interface gigabithethernet 0/0

If you are not already in interface configuration mode, enters interface configuration mode.

The redundant number argument is the redundant interface ID, such as redundant 1.

The port-channel number argument is the EtherChannel interface ID, such as port-channel 1.

See the “Enabling the Physical Interface and Configuring Ethernet Parameters” section for a description of the physical interface ID.

Append the subinterface ID to the physical or redundant interface ID separated by a period (.).

In multiple context mode, enter the mapped_name if one was assigned using the allocate-interface command.

Step 2

Do one of the following:

 

ipv6 address autoconfig

 

hostname(config-if)# ipv6 address autoconfig

Enables stateless autoconfiguration on the interface. Enabling stateless autoconfiguration on the interface configures IPv6 addresses based on prefixes received in Router Advertisement messages. A link-local address, based on the Modified EUI-64 interface ID, is automatically generated for the interface when stateless autoconfiguration is enabled.

Note Although RFC 4862 specifies that hosts configured for stateless autoconfiguration do not send Router Advertisement messages, the ASA does send Router Advertisement messages in this case. See the ipv6 nd suppress-ra command to suppress messages.

 

ipv6 address ipv6-address/prefix-length [ standby ipv6-address ]

 

hostname(config-if)# ipv6 address 2001:0DB8::BA98:0:3210/48

Assigns a global address to the interface. When you assign a global address, the link-local address is automatically created for the interface.

standby specifies the interface address used by the secondary unit or failover group in a failover pair.

See the “IPv6 Addresses” section for more information about IPv6 addressing.

 

ipv6 address ipv6-prefix/prefix-length eui-64

 

hostname(config-if)# ipv6 address 2001:0DB8::BA98::/48 eui-64

Assigns a global address to the interface by combining the specified prefix with an interface ID generated from the interface MAC address using the Modified EUI-64 format. When you assign a global address, the link-local address is automatically created for the interface.

Y ou do not need to specify the standby address; the interface ID will be generated automatically.

See the “IPv6 Addresses” section for more information about IPv6 addressing.

Step 3

(Optional)

ipv6 nd suppress-ra

 

hostname(config-if)# ipv6 nd suppress-ra

Suppresses Router Advertisement messages on an interface. By default, Router Advertisement messages are automatically sent in response to router solicitation messages. You may want to disable these messages on any interface for which you do not want the ASA to supply the IPv6 prefix (for example, the outside interface).

Step 4

(Optional)

ipv6 nd dad attempts value

 

hostname(config-if)# ipv6 nd dad attempts 3

Changes the number of duplicate address detection attempts. The value argument can be any value from 0 to 600. Setting the value argument to 0 disables duplicate address detection on the interface.

By default, the number of times an interface performs duplicate address detection is 1. See the “Duplicate Address Detection” section for more information.

Step 5

(Optional)

ipv6 nd ns-interval value

 

hostname(config-if)# ipv6 nd ns-interval 2000

Changes the neighbor solicitation message interval. When you configure an interface to send out more than one duplicate address detection attempt with the ipv6 nd dad attempts command, this command configures the interval at which the neighbor solicitation messages are sent out. By default, they are sent out once every 1000 milliseconds. The value argument can be from 1000 to 3600000 milliseconds.

Note Changing this value changes it for all neighbor solicitation messages sent out on the interface, not just those used for duplicate address detection.

Step 6

(Optional)

ipv6 enforce-eui64 if_name
 
hostname(config)# ipv6 enforce-eui64 inside

Enforces the use of Modified EUI-64 format interface identifiers in IPv6 addresses on a local link.

The if_name argument is the name of the interface, as specified by the nameif command, on which you are enabling the address format enforcement.

See the “Modified EUI-64 Interface IDs” section for more information.

Allowing Same Security Level Communication

By default, interfaces on the same security level cannot communicate with each other, and packets cannot enter and exit the same interface. This section describes how to enable inter-interface communication when interfaces are on the same security level, and how to enable intra-interface communication.

Information About Inter-Interface Communication

Allowing interfaces on the same security level to communicate with each other provides the following benefits:

  • You can configure more than 101 communicating interfaces.

If you use different levels for each interface and do not assign any interfaces to the same security level, you can configure only one interface per level (0 to 100).

  • You want traffic to flow freely between all same security interfaces without access lists.

If you enable same security interface communication, you can still configure interfaces at different security levels as usual.

Information About Intra-Interface Communication

Intra-interface communication might be useful for VPN traffic that enters an interface, but is then routed out the same interface. The VPN traffic might be unencrypted in this case, or it might be reencrypted for another VPN connection. For example, if you have a hub and spoke VPN network, where the ASA is the hub, and remote VPN networks are spokes, for one spoke to communicate with another spoke, traffic must go into the ASA and then out again to the other spoke.

note.gif

Noteblank.gif All traffic allowed by this feature is still subject to firewall rules. Be careful not to create an asymmetric routing situation that can cause return traffic not to traverse the ASA.

Detailed Steps

 

Command
Purpose

same-security-traffic permit inter-interface

Enables interfaces on the same security level so that they can communicate with each other.

same-security-traffic permit intra-interface

Enables communication between hosts connected to the same interface.

 

Monitoring Interfaces

To monitor interfaces, enter one of the following commands:

 

Command
Purpose

show interface

Displays interface statistics.
show interface ip brief

Displays interface IP addresses and status.

Configuration Examples for Interfaces in Routed Mode

This section includes the following topics:

ASA 5505 Example

The following example configures three VLAN interfaces for the Base license. The third home interface cannot forward traffic to the business interface.

hostname(config)# interface vlan 100
hostname(config-if)# nameif outside
hostname(config-if)# security-level 0
hostname(config-if)# ip address dhcp
hostname(config-if)# no shutdown
 
hostname(config-if)# interface vlan 200
hostname(config-if)# nameif business
hostname(config-if)# security-level 100
hostname(config-if)# ip address 10.1.1.1 255.255.255.0
hostname(config-if)# no shutdown
 
hostname(config-if)# interface vlan 300
hostname(config-if)# no forward interface vlan 200
hostname(config-if)# nameif home
hostname(config-if)# security-level 50
hostname(config-if)# ip address 10.2.1.1 255.255.255.0
hostname(config-if)# no shutdown
 

Feature History for Interfaces in Routed Mode

Table 8-1 lists the release history for this feature.

 

Table 8-1 Feature History for Interfaces

Feature Name
Releases
Feature Information

Increased VLANs

7.0(5)

Increased the following limits:

  • ASA5510 Base license VLANs from 0 to 10.
  • ASA5510 Security Plus license VLANs from 10 to 25.
  • ASA5520 VLANs from 25 to 100.
  • ASA5540 VLANs from 100 to 200.

Increased VLANs

7.2(2)

The maximum number of VLANs for the Security Plus license on the ASA 5505 was increased from 5 (3 fully functional; 1 failover; one restricted to a backup interface) to 20 fully functional interfaces. In addition, the number of trunk ports was increased from 1 to 8. Now there are 20 fully functional interfaces, you do not need to use the backup interface command to cripple a backup ISP interface; you can use a fully-functional interface for it. The backup interface command is still useful for an Easy VPN configuration.

VLAN limits were also increased for the ASA 5510 (from 10 to 50 for the Base license, and from 25 to 100 for the Security Plus license), the ASA 5520 (from 100 to 150), the ASA 5550 (from 200 to 250).

Gigabit Ethernet Support for the ASA 5510 Security Plus License

7.2(3)

The ASA 5510 now supports GE (Gigabit Ethernet) for port 0 and 1 with the Security Plus license. If you upgrade the license from Base to Security Plus, the capacity of the external Ethernet0/0 and Ethernet0/1 ports increases from the original FE (Fast Ethernet) (100 Mbps) to GE (1000 Mbps). The interface names will remain Ethernet 0/0 and Ethernet 0/1. Use the speed command to change the speed on the interface and use the show interface command to see what speed is currently configured for each interface.

Native VLAN support for the ASA 5505

7.2(4)/8.0(4)

You can now include the native VLAN in an ASA 5505 trunk port.

We introduced the following command: switchport trunk native vlan.

Jumbo packet support for the ASA 5580

8.1(1)

The Cisco ASA 5580 supports jumbo frames. A jumbo frame is an Ethernet packet larger than the standard maximum of 1518 bytes (including Layer 2 header and FCS), up to 9216 bytes. You can enable support for jumbo frames for all interfaces by increasing the amount of memory to process Ethernet frames. Assigning more memory for jumbo frames might limit the maximum use of other features, such as access lists.

We introduced the following command: jumbo-frame reservation.

Increased VLANs for the ASA 5580

8.1(2)

The number of VLANs supported on the ASA 5580 are increased from 100 to 250.

IPv6 support for transparent mode

8.2(1)

IPv6 support was introduced for transparent firewall mode.

Support for Pause Frames for Flow Control on the ASA 5580 10 Gigabit Ethernet Interfaces

8.2(2)

You can now enable pause (XOFF) frames for flow control.

We introduced the following command: flowcontrol.