Cisco ASA Services Module CLI Configuration Guide, 8.5
Configuring Multiple Context Mode
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Configuring Multiple Context Mode

Table Of Contents

Configuring Multiple Context Mode

Information About Security Contexts

Common Uses for Security Contexts

Context Configuration Files

Context Configurations

System Configuration

Admin Context Configuration

How the ASA Classifies Packets

Valid Classifier Criteria

Classification Examples

Cascading Security Contexts

Management Access to Security Contexts

System Administrator Access

Context Administrator Access

Information About Resource Management

Resource Limits

Default Class

Class Members

Information About MAC Addresses

Default MAC Address

Interaction with Manual MAC Addresses

Failover MAC Addresses

MAC Address Format

Licensing Requirements for Multiple Context Mode

Guidelines and Limitations

Default Settings

Configuring Multiple Contexts

Task Flow for Configuring Multiple Context Mode

Enabling or Disabling Multiple Context Mode

Enabling Multiple Context Mode

Restoring Single Context Mode

Configuring a Class for Resource Management

Configuring a Security Context

Automatically Assigning MAC Addresses to Context Interfaces

Changing Between Contexts and the System Execution Space

Managing Security Contexts

Removing a Security Context

Changing the Admin Context

Changing the Security Context URL

Reloading a Security Context

Reloading by Clearing the Configuration

Reloading by Removing and Re-adding the Context

Monitoring Security Contexts

Viewing Context Information

Viewing Resource Allocation

Viewing Resource Usage

Monitoring SYN Attacks in Contexts

Viewing Assigned MAC Addresses

Viewing MAC Addresses in the System Configuration

Viewing MAC Addresses Within a Context

Configuration Examples for Multiple Context Mode

Feature History for Multiple Context Mode


Configuring Multiple Context Mode


This chapter describes how to configure multiple security contexts on the ASASM and includes the following sections:

Information About Security Contexts

Licensing Requirements for Multiple Context Mode

Guidelines and Limitations

Default Settings

Configuring Multiple Contexts

Changing Between Contexts and the System Execution Space

Managing Security Contexts

Monitoring Security Contexts

Configuration Examples for Multiple Context Mode

Feature History for Multiple Context Mode

Information About Security Contexts

You can partition a single ASASM into multiple virtual devices, known as security contexts. Each context is an independent device, with its own security policy, interfaces, and administrators. Multiple contexts are similar to having multiple standalone devices. Many features are supported in multiple context mode, including routing tables, firewall features, IPS, and management. Some features are not supported, including VPN and dynamic routing protocols.


Note When the ASASM is configured for security contexts (for example, for Active/Active Stateful Failover), IPsec or SSL VPN cannot be enabled. Therefore, these features are unavailable.


This section provides an overview of security contexts and includes the following topics:

Common Uses for Security Contexts

Context Configuration Files

How the ASA Classifies Packets

Cascading Security Contexts

Management Access to Security Contexts

Information About Resource Management

Information About MAC Addresses

Common Uses for Security Contexts

You might want to use multiple security contexts in the following situations:

You are a service provider and want to sell security services to many customers. By enabling multiple security contexts on the ASASM, you can implement a cost-effective, space-saving solution that keeps all customer traffic separate and secure, and also eases configuration.

You are a large enterprise or a college campus and want to keep departments completely separate.

You are an enterprise that wants to provide distinct security policies to different departments.

You have any network that requires more than one ASASM.

Context Configuration Files

This section describes how the ASASM implements multiple context mode configurations and includes the following sections:

Context Configurations

System Configuration

Admin Context Configuration

Context Configurations

The ASASM includes a configuration for each context that identifies the security policy, interfaces, and almost all the options you can configure on a standalone device. You can store context configurations on the internal flash memory or the external flash memory card, or you can download them from a TFTP, FTP, or HTTP(S) server.

System Configuration

The system administrator adds and manages contexts by configuring each context configuration location, allocated interfaces, and other context operating parameters in the system configuration, which, like a single mode configuration, is the startup configuration. The system configuration identifies basic settings for the ASASM. The system configuration does not include any network interfaces or network settings for itself; rather, when the system needs to access network resources (such as downloading the contexts from the server), it uses one of the contexts that is designated as the admin context. The system configuration does include a specialized failover interface for failover traffic only.

Admin Context Configuration

The admin context is just like any other context, except that when a user logs in to the admin context, then that user has system administrator rights and can access the system and all other contexts. The admin context is not restricted in any way, and can be used as a regular context. However, because logging into the admin context grants you administrator privileges over all contexts, you might need to restrict access to the admin context to appropriate users. The admin context must reside on flash memory, and not remotely.

If your system is already in multiple context mode, or if you convert from single mode, the admin context is created automatically as a file on the internal flash memory called admin.cfg. This context is named "admin." If you do not want to use admin.cfg as the admin context, you can change the admin context.

How the ASA Classifies Packets

Each packet that enters the ASASM must be classified, so that the ASASM can determine to which context to send a packet. This section includes the following topics:

Valid Classifier Criteria

Classification Examples


Note If the destination MAC address is a multicast or broadcast MAC address, the packet is duplicated and delivered to each context.


Valid Classifier Criteria

This section describes the criteria used by the classifier and includes the following topics:

Unique Interfaces

Unique MAC Addresses

NAT Configuration


Note For management traffic destined for an interface, the interface IP address is used for classification.

The routing table is not used for packet classification.


Unique Interfaces

If only one context is associated with the ingress interface, the ASASM classifies the packet into that context. In transparent firewall mode, unique interfaces for contexts are required, so this method is used to classify packets at all times.

Unique MAC Addresses

If multiple contexts share an interface, then the classifier uses the interface MAC address, or for the ASASM, the backplane MAC address. The ASASM lets you assign a different MAC address in each context to the same shared interface. By default, shared interfaces do not have unique MAC addresses; the interface uses the burned-in MAC address in every context. An upstream router cannot route directly to a context without unique MAC addresses. You can set the MAC addresses manually when you configure each interface (see the "Configuring the MAC Address and MTU" section), or you can automatically generate MAC addresses (see the "Automatically Assigning MAC Addresses to Context Interfaces" section).

NAT Configuration

If you do not use unique MAC addresses, then the mapped addresses in your NAT configuration are used to classify packets. We recommend using MAC addresses instead of NAT, so that traffic classification can occur regardless of the completeness of the NAT configuration.

Classification Examples

Figure 6-1 shows multiple contexts sharing an outside interface. The classifier assigns the packet to Context B because Context B includes the MAC address to which the router sends the packet.

Figure 6-1 Packet Classification with a Shared Interface using MAC Addresses

Note that all new incoming traffic must be classified, even from inside networks. Figure 6-2 shows a host on the Context B inside network accessing the Internet. The classifier assigns the packet to Context B because the ingress interface is Gigabit Ethernet 0/1.3, which is assigned to Context B.

Figure 6-2 Incoming Traffic from Inside Networks

For transparent firewalls, you must use unique interfaces. Figure 6-3 shows a host on the Context B inside network accessing the Internet. The classifier assigns the packet to Context B because the ingress interface is Gigabit Ethernet 1/0.3, which is assigned to Context B.

Figure 6-3 Transparent Firewall Contexts

Cascading Security Contexts

Placing a context directly in front of another context is called cascading contexts; the outside interface of one context is the same interface as the inside interface of another context. You might want to cascade contexts if you want to simplify the configuration of some contexts by configuring shared parameters in the top context.


Note Cascading contexts requires that you configure unique MAC addresses for each context interface. Because of the limitations of classifying packets on shared interfaces without MAC addresses, we do not recommend using cascading contexts without unique MAC addresses.


Figure 6-4 shows a gateway context with two contexts behind the gateway.

Figure 6-4 Cascading Contexts

Management Access to Security Contexts

The ASASM provides system administrator access in multiple context mode as well as access for individual context administrators. The following sections describe logging in as a system administrator or as a context administrator:

System Administrator Access

Context Administrator Access

System Administrator Access

You can access the ASASM as a system administrator in two ways:

Access the ASASM console.

From the console, you access the system execution space, which means that any commands you enter affect only the system configuration or the running of the system (for run-time commands).

Access the admin context using Telnet, SSH, or ASDM.

See Chapter 34 "Configuring Management Access," to enable Telnet, SSH, and SDM access.

As the system administrator, you can access all contexts.

When you change to a context from admin or the system, your username changes to the default "enable_15" username. If you configured command authorization in that context, you need to either configure authorization privileges for the "enable_15" user, or you can log in as a different name for which you provide sufficient privileges in the command authorization configuration for the context. To log in with a username, enter the login command. For example, you log in to the admin context with the username "admin." The admin context does not have any command authorization configuration, but all other contexts include command authorization. For convenience, each context configuration includes a user "admin" with maximum privileges. When you change from the admin context to context A, your username is altered, so you must log in again as "admin" by entering the login command. When you change to context B, you must again enter the login command to log in as "admin."

The system execution space does not support any AAA commands, but you can configure its own enable password, as well as usernames in the local database to provide individual logins.

Context Administrator Access

You can access a context using Telnet, SSH, or ASDM. If you log in to a non-admin context, you can only access the configuration for that context. You can provide individual logins to the context. See Chapter 34 "Configuring Management Access," to enable Telnet, SSH, and SDM access and to configure management authentication.

Information About Resource Management

By default, all security contexts have unlimited access to the resources of the ASASM, except where maximum limits per context are enforced. However, if you find that one or more contexts use too many resources, and they cause other contexts to be denied connections, for example, then you can configure resource management to limit the use of resources per context.

The ASASM manages resources by assigning contexts to resource classes. Each context uses the resource limits set by the class.

This section includes the following topics:

Resource Limits

Default Class

Class Members

Resource Limits

When you create a class, the ASASM does not set aside a portion of the resources for each context assigned to the class; rather, the ASASM sets the maximum limit for a context. If you oversubscribe resources, or allow some resources to be unlimited, a few contexts can "use up" those resources, potentially affecting service to other contexts.

You can set the limit for individual resources, as a percentage (if there is a hard system limit) or as an absolute value.

You can oversubscribe the ASASM by assigning more than 100 percent of a resource across all contexts. For example, you can set the Bronze class to limit connections to 20 percent per context, and then assign 10 contexts to the class for a total of 200 percent. If contexts concurrently use more than the system limit, then each context gets less than the 20 percent you intended. (See Figure 6-5.)

Figure 6-5 Resource Oversubscription

If you assign an absolute value to a resource across all contexts that exceeds the practical limit of the ASASM, then the performance of the ASASM might be impaired.

The ASASM lets you assign unlimited access to one or more resources in a class, instead of a percentage or absolute number. When a resource is unlimited, contexts can use as much of the resource as the system has available or that is practically available. For example, Context A, B, and C are in the Silver Class, which limits each class member to 1 percent of the connections, for a total of 3 percent; but the three contexts are currently only using 2 percent combined. Gold Class has unlimited access to connections. The contexts in the Gold Class can use more than the 97 percent of "unassigned" connections; they can also use the 1 percent of connections not currently in use by Context A, B, and C, even if that means that Context A, B, and C are unable to reach their 3 percent combined limit. (See Figure 6-6.) Setting unlimited access is similar to oversubscribing the ASASM, except that you have less control over how much you oversubscribe the system.

Figure 6-6 Unlimited Resources

Default Class

All contexts belong to the default class if they are not assigned to another class; you do not have to actively assign a context to the default class.

If a context belongs to a class other than the default class, those class settings always override the default class settings. However, if the other class has any settings that are not defined, then the member context uses the default class for those limits. For example, if you create a class with a 2 percent limit for all concurrent connections, but no other limits, then all other limits are inherited from the default class. Conversely, if you create a class with a limit for all resources, the class uses no settings from the default class.

By default, the default class provides unlimited access to resources for all contexts, except for the following limits, which are by default set to the maximum allowed per context:

Telnet sessions—5 sessions.

SSH sessions—5 sessions.

IPsec sessions—5 sessions.

MAC addresses—65,535 entries.

Figure 6-7 shows the relationship between the default class and other classes. Contexts A and C belong to classes with some limits set; other limits are inherited from the default class. Context B inherits no limits from default because all limits are set in its class, the Gold class. Context D was not assigned to a class, and is by default a member of the default class.

Figure 6-7 Resource Classes

Class Members

To use the settings of a class, assign the context to the class when you define the context. All contexts belong to the default class if they are not assigned to another class; you do not have to actively assign a context to default. You can only assign a context to one resource class. The exception to this rule is that limits that are undefined in the member class are inherited from the default class; so in effect, a context could be a member of default plus another class.

Information About MAC Addresses

To allow contexts to share interfaces, you should assign unique MAC addresses to each shared context interface.

The MAC address is used to classify packets within a context. If you share an interface, but do not have unique MAC addresses for the interface in each context, then other classification methods are attempted that might not provide full coverage. See the "How the ASA Classifies Packets" section for information about classifying packets.

In the rare circumstance that the generated MAC address conflicts with another private MAC address in your network, you can manually set the MAC address for the interface within the context. See the "Configuring the MAC Address and MTU" section to manually set the MAC address.

This section includes the following topics:

Default MAC Address

Interaction with Manual MAC Addresses

Failover MAC Addresses

MAC Address Format

Default MAC Address

If you disable MAC address generation, all VLAN interfaces use the same MAC address, derived from the backplane MAC address.

See the following sections for your release for additional information about automatic MAC address generation. See also the "MAC Address Format" section.

8.5(1.7) and Later

Automatic MAC address generation is enabled—Uses an autogenerated prefix. The ASASM autogenerates the prefix based on the last two bytes of the backplane MAC address. You cannot use the legacy auto-generation method (without a prefix).


Note To maintain hitless upgrade for failover pairs, the ASASM does not convert an existing auto-generation configuration upon a reload if failover is enabled. However, we strongly recommend that you manually change to the prefix method of generation when using failover. Without the prefix method, ASASMs installed in different slot numbers experience a MAC address change upon failover, and can experience traffic interruption. After upgrading, to use the prefix method of MAC address generation, reenable MAC address autogeneration to use a prefix.


Earlier Releases

Automatic MAC address generation is enabled—Uses the legacy auto-generation method (without a prefix).

Interaction with Manual MAC Addresses

If you manually assign a MAC address and also enable auto-generation, then the manually assigned MAC address is used. If you later remove the manual MAC address, the auto-generated address is used.

Because auto-generated addresses (when using a prefix) start with A2, you cannot start manual MAC addresses with A2 if you also want to use auto-generation.

Failover MAC Addresses

For use with failover, the ASASM generates both an active and standby MAC address for each interface. 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. See the "MAC Address Format" section for more information.

MAC Address Format

The MAC address format without a prefix is a legacy version not supported on newer ASA versions.

MAC Address Format Using a Prefix

The ASASM generates the MAC address using the following format:

A2xx.yyzz.zzzz

Where xx.yy is a user-defined prefix or an autogenerated prefix based on the last two bytes of the backplane MAC address, and zz.zzzz is an internal counter generated by the ASASM. For the standby MAC address, the address is identical except that the internal counter is increased by 1.

For an example of how the prefix is used, if you set a prefix of 77, then the ASASM converts 77 into the hexadecimal value 004D (yyxx). When used in the MAC address, the prefix is reversed (xxyy) to match the ASASM native form:

A24D.00zz.zzzz

For a prefix of 1009 (03F1), the MAC address is:

A2F1.03zz.zzzz

MAC Address Format Without a Prefix (Legacy Method; Not Available in 8.5(1.7) and Later)

Without a prefix, the MAC address is generated using the following format:

Active unit MAC address: 12_slot.port_subid.contextid.

Standby unit MAC address: 02_slot.port_subid.contextid.

The port is the interface port. The subid is an internal ID for the subinterface, which is not viewable. The contextid is an internal ID for the context, viewable with the show context detail command. For example, the interface GigabitEthernet 0/1.200 in the context with the ID 1 has the following generated MAC addresses, where the internal ID for subinterface 200 is 31:

Active: 1200.0131.0001

Standby: 0200.0131.0001

This MAC address generation method does not allow for persistent MAC addresses across reloads, does not allow for multiple ASASMs on the same network segment (because unique MAC addresses are not guaranteed), and does not prevent overlapping MAC addresses with manually assigned MAC addresses. We recommend using a prefix with the MAC address generation to avoid these issues.

Licensing Requirements for Multiple Context Mode

Model
License Requirement

ASASM

Base License: 2 contexts.

Optional licenses: 5, 10, 20, 50, 100, or 250 contexts.


Guidelines and Limitations

This section includes the guidelines and limitations for this feature.

Firewall Mode Guidelines

Supported in routed and transparent firewall mode.

Failover Guidelines

Active/Active mode failover is only supported in multiple context mode.

IPv6 Guidelines

Supports IPv6.

Model Guidelines

Does not support the ASA 5505.

Unsupported Features

Multiple context mode does not support the following features:

Dynamic routing protocols

Security contexts support only static routes. You cannot enable OSPF, RIP, or EIGRP in multiple context mode.

VPN

Multicast routing

Threat Detection

Phone Proxy

QoS

Unified Communications

Additional Guidelines

The context mode (single or multiple) is not stored in the configuration file, even though it does endure reboots. If you need to copy your configuration to another device, set the mode on the new device to match.

Default Settings

By default, the ASASM is in single context mode.

Configuring Multiple Contexts

This section describes how to configure multiple context mode, and includes the following topics:

Task Flow for Configuring Multiple Context Mode

Enabling or Disabling Multiple Context Mode

Configuring a Class for Resource Management

Configuring a Security Context

Automatically Assigning MAC Addresses to Context Interfaces

Task Flow for Configuring Multiple Context Mode

To configure multiple context mode, perform the following steps:


Step 1 Enable multiple context mode. See the "Enabling or Disabling Multiple Context Mode" section.

Step 2 (Optional) Configure classes for resource management. See the "Configuring a Class for Resource Management" section.

Step 3 Configure security contexts. See the "Configuring a Security Context" section.

Step 4 (Optional) Automatically assign MAC addresses to context interfaces. See the "Automatically Assigning MAC Addresses to Context Interfaces" section.

Step 5 Complete interface configuration in the context. See Chapter 7 "Configuring Interfaces (Routed Mode)," or Chapter 8 "Configuring Interfaces (Transparent Mode)."


Enabling or Disabling Multiple Context Mode

Your ASASM might already be configured for multiple security contexts depending on how you ordered it from Cisco. If you are upgrading, however, you might need to convert from single mode to multiple mode by following the procedures in this section.

This section includes the following topics:

Enabling Multiple Context Mode

Restoring Single Context Mode

Enabling Multiple Context Mode

When you convert from single mode to multiple mode, the ASASM converts the running configuration into two files: a new startup configuration that comprises the system configuration, and admin.cfg that comprises the admin context (in the root directory of the internal flash memory). The original running configuration is saved as old_running.cfg (in the root directory of the internal flash memory). The original startup configuration is not saved. The ASASM automatically adds an entry for the admin context to the system configuration with the name "admin."

Prerequisites

When you convert from single mode to multiple mode, the ASASM converts the running configuration into two files. The original startup configuration is not saved, so if it differs from the running configuration, you should back it up before proceeding.

The context mode (single or multiple) is not stored in the configuration file, even though it does endure reboots. If you need to copy your configuration to another device, set the mode on the new device to match.

Detailed Steps

Command
Purpose

mode multiple

Example:

hostname(config)# mode multiple

Changes to multiple context mode. You are prompted to reboot the ASASM.


Restoring Single Context Mode

To copy the old running configuration to the startup configuration and to change the mode to single mode, perform the following steps.

Prerequisites

Perform this procedure in the system execution space.

Detailed Steps

 
Command
Purpose

Step 1 

copy flash:old_running.cfg startup-config

Example:

hostname(config)# copy flash:old_running.cfg startup-config

Copies the backup version of your original running configuration to the current startup configuration.

Step 2 

mode single

Example:

hostname(config)# mode single

Sets the mode to single mode. You are prompted to reboot the ASASM.

Configuring a Class for Resource Management

To configure a class in the system configuration, perform the following steps. You can change the value of a particular resource limit by reentering the command with a new value.

Prerequisites

Perform this procedure in the system execution space.

Guidelines

Table 6-1 lists the resource types and the limits. See also the show resource types command.

Table 6-1 Resource Names and Limits 

Resource Name
Rate or Concurrent
Minimum and Maximum Number per Context
System Limit 1
Description

mac-addresses

Concurrent

N/A

65,535

For transparent firewall mode, the number of MAC addresses allowed in the MAC address table.

conns

Concurrent or Rate

N/A

Concurrent connections: See the "Supported Feature Licenses" section for the connection limit for your platform.

Rate: N/A

TCP or UDP connections between any two hosts, including connections between one host and multiple other hosts.

inspects

Rate

N/A

N/A

Application inspections.

hosts

Concurrent

N/A

N/A

Hosts that can connect through the ASASM.

asdm

Concurrent

1 minimum

5 maximum

200

ASDM management sessions.

Note ASDM sessions use two HTTPS connections: one for monitoring that is always present, and one for making configuration changes that is present only when you make changes. For example, the system limit of 32 ASDM sessions represents a limit of 64 HTTPS sessions.

ssh

Concurrent

1 minimum

5 maximum

100

SSH sessions.

syslogs

Rate

N/A

N/A

Syslog messages.

telnet

Concurrent

1 minimum

5 maximum

100

Telnet sessions.

xlates

Concurrent

N/A

N/A

Address translations.

1 If this column value is N/A, then you cannot set a percentage of the resource because there is no hard system limit for the resource.


Detailed Steps

 
Command
Purpose

Step 1 

class name

Example:

hostname(config)# threat-detection scanning-threat shun except ip-address 10.1.1.0 255.255.255.0

Specifies the class name and enters the class configuration mode. The name is a string up to 20 characters long. To set the limits for the default class, enter default for the name.

Step 2 

Do one or more of the following:

 

limit-resource all 0

Example:

hostname(config)# limit-resource all 0

Sets all resource limits (shown in Table 6-1) to be unlimited. For example, you might want to create a class that includes the admin context that has no limitations. The default class has all resources set to unlimited by default.

 

limit-resource [rate] resource_name number[%]

Example:

hostname(config)# limit-resource rate inspects 10

Sets a particular resource limit. For this particular resource, the limit overrides the limit set for all. Enter the rate argument to set the rate per second for certain resources. For resources that do not have a system limit, you cannot set the percentage (%) between 1 and 100; you can only set an absolute value. See Table 6-1 for resources for which you can set the rate per second and which do not have a system limit.

Examples

For example, to set the default class limit for conns to 10 percent instead of unlimited, enter the following commands:

hostname(config)# class default
hostname(config-class)# limit-resource conns 10%
 
   

All other resources remain at unlimited.

To add a class called gold, enter the following commands:

hostname(config)# class gold
hostname(config-class)# limit-resource mac-addresses 10000
hostname(config-class)# limit-resource conns 15%
hostname(config-class)# limit-resource rate conns 1000
hostname(config-class)# limit-resource rate inspects 500
hostname(config-class)# limit-resource hosts 9000
hostname(config-class)# limit-resource asdm 5
hostname(config-class)# limit-resource ssh 5
hostname(config-class)# limit-resource rate syslogs 5000
hostname(config-class)# limit-resource telnet 5
hostname(config-class)# limit-resource xlates 36000
 
   

Configuring a Security Context

The security context definition in the system configuration identifies the context name, configuration file URL, and interfaces that a context can use.

Prerequisites

Perform this procedure in the system execution space.

For the ASASM, assign VLANs to the ASASM on the switch according to Chapter 2 "Configuring the Switch for Use with the ASA Services Module."

If you do not have an admin context (for example, if you clear the configuration) then you must first specify the admin context name by entering the following command:

hostname(config)# admin-context name

Although this context name does not exist yet in your configuration, you can subsequently enter the context name command to match the specified name to continue the admin context configuration.

Detailed Steps

 
Command
Purpose

Step 1 

context name

Example:

hostname(config)# context administrator

Adds or modifies a context. The name is a string up to 32 characters long. This name is case sensitive, so you can have two contexts named "customerA" and "CustomerA," for example. You can use letters, digits, or hyphens, but you cannot start or end the name with a hyphen.

"System" or "Null" (in upper or lower case letters) are reserved names, and cannot be used.

Step 2 

(Optional)

description text

Example:

hostname(config)# description Administrator Context

Adds a description for this context.

Step 3 

To allocate a physical interface:

allocate-interface physical_interface [mapped_name] [visible | invisible]

To allocate one or more subinterfaces:

allocate-interface physical_interface.subinterface[-physical_ interface.subinterface] [mapped_name[-mapped_name]] [visible | invisible]

Example:
hostname(config-ctx)# allocate-interface 
gigabitethernet0/1.100 int1
hostname(config-ctx)# allocate-interface 
gigabitethernet0/1.200 int2
hostname(config-ctx)# allocate-interface 
gigabitethernet0/2.300-gigabitethernet0/2.
305 int3-int8

Specifies the interfaces you can use in the context. Do not include a space between the interface type and the port number.

Enter these commands multiple times to specify different ranges. If you remove an allocation with the no form of this command, then any context commands that include this interface are removed from the running configuration.

You can assign the same interfaces to multiple contexts in routed mode, if desired.

The mapped_name is an alphanumeric alias for the interface that can be used within the context instead of the interface ID. If you do not specify a mapped name, the interface ID is used within the context. For security purposes, you might not want the context administrator to know which interfaces are being used by the context. A mapped name must start with a letter, end with a letter or digit, and have as interior characters only letters, digits, or an underscore. For example, you can use the following names:

int0, inta, int_0
 
        

If you specify a range of subinterfaces, you can specify a matching range of mapped names. Follow these guidelines for ranges:

The mapped name must consist of an alphabetic portion followed by a numeric portion. The alphabetic portion of the mapped name must match for both ends of the range. For example, enter the following range:

int0-int10
 
        

If you enter gig0/1.1-gig0/1.5 happy1-sad5, for example, the command fails.

The numeric portion of the mapped name must include the same quantity of numbers as the subinterface range. For example, both ranges include 100 interfaces:

gigabitethernet0/0.100-gigabitethernet0/0.199 
int1-int100
 
        

If you enter gig0/0.100-gig0/0.199 int1-int15, for example, the command fails.

Specify visible to see the real interface ID in the show interface command if you set a mapped name. The default invisible keyword shows only the mapped name.

Step 4 

config-url url

Example:
hostname(config-ctx)# config-url 
ftp://user1:passw0rd@10.1.1.1/configlets/t
est.cfg

Identifies the URL from which the system downloads the context configuration. When you add a context URL, the system immediately loads the context so that it is running, if the configuration is available.

Note Enter the allocate-interface command(s) before you enter the config-url command. If you enter the config-url command first, the ASASM loads the context configuration immediately. If the context contains any commands that refer to (not yet configured) interfaces, those commands fail.

The filename does not require a file extension, although we recommend using ".cfg". The server must be accessible from the admin context. If the configuration file is not available, you see the following message:

WARNING: Could not fetch the URL disk:/url
INFO: Creating context with default config
 
        

For non-HTTP(S) URL locations, after you specify the URL, you can then change to the context, configure it at the CLI, and enter the write memory command to write the file to the URL location. (HTTP(S) is read only).

Note The admin context file must be stored on the internal flash memory.

Available URL types include: disknumber (for flash memory), ftp, http, https, or tftp.

To change the URL, reenter the config-url command with a new URL. See the "Changing the Security Context URL" section for more information about changing the URL.

Step 5 

(Optional)

member class_name

Example:
hostname(config-ctx)# member gold

Assigns the context to a resource class. If you do not specify a class, the context belongs to the default class. You can only assign a context to one resource class.

Step 6 

(Optional)

join-failover-group {1 | 2)

Example:

hostname(config-ctx)# join-failover-group 2

Assigns a context to a failover group in Active/Active failover. By default, contexts are in group 1. The admin context must always be in group 1.

See the "Configuring the Primary Failover Unit" section for detailed information about failover groups.

Examples

The following example sets the admin context to be "administrator," creates a context called "administrator" on the internal flash memory, and then adds two contexts from an FTP server:

hostname(config)# admin-context administrator
hostname(config)# context administrator
hostname(config-ctx)# allocate-interface gigabitethernet0/0.1
hostname(config-ctx)# allocate-interface gigabitethernet0/1.1
hostname(config-ctx)# config-url flash:/admin.cfg
 
   
hostname(config-ctx)# context test
hostname(config-ctx)# allocate-interface gigabitethernet0/0.100 int1
hostname(config-ctx)# allocate-interface gigabitethernet0/0.102 int2
hostname(config-ctx)# allocate-interface gigabitethernet0/0.110-gigabitethernet0/0.115 
int3-int8
hostname(config-ctx)# config-url ftp://user1:passw0rd@10.1.1.1/configlets/test.cfg
hostname(config-ctx)# member gold
 
   
 
   
hostname(config-ctx)# context sample
hostname(config-ctx)# allocate-interface gigabitethernet0/1.200 int1
hostname(config-ctx)# allocate-interface gigabitethernet0/1.212 int2
hostname(config-ctx)# allocate-interface gigabitethernet0/1.230-gigabitethernet0/1.235 
int3-int8
hostname(config-ctx)# config-url ftp://user1:passw0rd@10.1.1.1/configlets/sample.cfg
hostname(config-ctx)# member silver
 
   

Automatically Assigning MAC Addresses to Context Interfaces

This section describes how to configure auto-generation of MAC addresses.

The MAC address is used to classify packets within a context. See the "Information About MAC Addresses" section for more information, especially if you are upgrading from an earlier ASA version. See also the "Viewing Assigned MAC Addresses" section.

Guidelines

When you configure a nameif command for the interface in a context, the new MAC address is generated immediately. If you enable this feature after you configure context interfaces, then MAC addresses are generated for all interfaces immediately after you enable it. If you disable this feature, the MAC address for each interface reverts to the default MAC address. For example, subinterfaces of GigabitEthernet 0/1 revert to using the MAC address of GigabitEthernet 0/1.

In the rare circumstance that the generated MAC address conflicts with another private MAC address in your network, you can manually set the MAC address for the interface within the context. See the "Configuring the MAC Address and MTU" section to manually set the MAC address.

Detailed Steps

Command
Purpose

mac-address auto [prefix prefix]

Example:

hostname(config)# mac-address auto prefix 19

Automatically assign private MAC addresses to each context interface.

The prefix is a decimal value between 0 and 65535. This prefix is converted to a 4-digit hexadecimal number, and used as part of the MAC address. The prefix ensures that each ASASM uses unique MAC addresses, so you can have multiple ASASMs on a network segment, for example. See the "MAC Address Format" section for more information about how the prefix is used.


Changing Between Contexts and the System Execution Space

If you log in to the system execution space (or the admin context using Telnet or SSH), you can change between contexts and perform configuration and monitoring tasks within each context. The running configuration that you edit in a configuration mode, or that is used in the copy or write commands, depends on your location. When you are in the system execution space, the running configuration consists only of the system configuration; when you are in a context, the running configuration consists only of that context. For example, you cannot view all running configurations (system plus all contexts) by entering the show running-config command. Only the current configuration displays.

To change between the system execution space and a context, or between contexts, see the following commands:

Command
Purpose

changeto context name

Changes to a context. The prompt changes to the following:

hostname/name#
 
        

changeto system

Changes to the system execution space. The prompt changes to the following:

hostname#
 
        

Managing Security Contexts

This section describes how to manage security contexts and includes the following topics:

Removing a Security Context

Changing the Admin Context

Changing the Security Context URL

Reloading a Security Context

Removing a Security Context

You can only remove a context by editing the system configuration. You cannot remove the current admin context, unless you remove all contexts using the clear context command.


Note If you use failover, there is a delay between when you remove the context on the active unit and when the context is removed on the standby unit. You might see an error message indicating that the number of interfaces on the active and standby units are not consistent; this error is temporary and can be ignored.


Prerequisites

Perform this procedure in the system execution space.

Detailed Steps

Command
Purpose

no context name

Removes a single context. All context commands are also removed.

clear context

Removes all contexts (including the admin context).


Changing the Admin Context

The system configuration does not include any network interfaces or network settings for itself; rather, when the system needs to access network resources (such as downloading the contexts from the server), it uses one of the contexts that is designated as the admin context.

The admin context is just like any other context, except that when a user logs in to the admin context, then that user has system administrator rights and can access the system and all other contexts. The admin context is not restricted in any way, and can be used as a regular context. However, because logging into the admin context grants you administrator privileges over all contexts, you might need to restrict access to the admin context to appropriate users.

Guidelines

You can set any context to be the admin context, as long as the configuration file is stored in the internal flash memory.

Prerequisites

Perform this procedure in the system execution space.

Detailed Steps

Command
Purpose

admin-context context_name

Example:

hostname(config)# admin-context administrator

Sets the admin context. Any remote management sessions, such as Telnet, SSH, or HTTPS, that are connected to the admin context are terminated. You must reconnect to the new admin context.

Note A few system commands, including ntp server, identify an interface name that belongs to the admin context. If you change the admin context, and that interface name does not exist in the new admin context, be sure to update any system commands that refer to the interface.


Changing the Security Context URL

This section describes how to change the context URL.

Guidelines

You cannot change the security context URL without reloading the configuration from the new URL. The ASASM merges the new configuration with the current running configuration.

Reentering the same URL also merges the saved configuration with the running configuration.

A merge adds any new commands from the new configuration to the running configuration.

If the configurations are the same, no changes occur.

If commands conflict or if commands affect the running of the context, then the effect of the merge depends on the command. You might get errors, or you might have unexpected results. If the running configuration is blank (for example, if the server was unavailable and the configuration was never downloaded), then the new configuration is used.

If you do not want to merge the configurations, you can clear the running configuration, which disrupts any communications through the context, and then reload the configuration from the new URL.

Prerequisites

Perform this procedure in the system execution space.

Detailed Steps

 
Command
Purpose

Step 1 

(Optional, if you do not want to perform a merge)

changeto context name
clear configure all
Example:

hostname(config)# changeto context ctx1

hostname/ctx1(config)# clear configure all

Changes to the context and clears its configuration. If you want to perform a merge, skip to Step 2.

Step 2 

changeto system

Example:

hostname/ctx1(config)# changeto system

hostname(config)#

Changes to the system execution space.

Step 3 

context name

Example:

hostname(config)# context ctx1

Enters the context configuration mode for the context you want to change.

Step 4 

config-url new_url

Example:

hostname(config)# config-url ftp://user1:passw0rd@10.1.1.1/configlets/c tx1.cfg

Enters the new URL. The system immediately loads the context so that it is running.

Reloading a Security Context

You can reload the context in two ways:

Clear the running configuration and then import the startup configuration.

This action clears most attributes associated with the context, such as connections and NAT tables.

Remove the context from the system configuration.

This action clears additional attributes, such as memory allocation, which might be useful for troubleshooting. However, to add the context back to the system requires you to respecify the URL and interfaces.

This section includes the following topics:

Reloading by Clearing the Configuration

Reloading by Removing and Re-adding the Context

Reloading by Clearing the Configuration

To reload the context by clearing the context configuration, and reloading the configuration from the URL, perform the following steps.

Detailed Steps

 
Command
Purpose

Step 1 

changeto context name

Example:

hostname(comfig)# changeto context ctx1

hostname/ctx1(comfig)#

Changes to the context that you want to reload.

Step 2 

clear configure all

Example:

hostname/ctx1(config)# clear configure all

Clears the running configuration. This command clears all connections.

Step 3 

copy startup-config running-config

Example:

hostname/ctx1(config)# copy startup-config running-config

Reloads the configuration. The ASASM copies the configuration from the URL specified in the system configuration. You cannot change the URL from within a context.

Reloading by Removing and Re-adding the Context

To reload the context by removing the context and then re-adding it, perform the steps in the following sections:

1. "Removing a Security Context" section

2. "Configuring a Security Context" section

Monitoring Security Contexts

This section describes how to view and monitor context information and includes the following topics:

Viewing Context Information

Viewing Context Information

Viewing Resource Allocation

Viewing Resource Usage

Monitoring SYN Attacks in Contexts

Viewing Assigned MAC Addresses

Viewing Context Information

From the system execution space, you can view a list of contexts including the name, allocated interfaces, and configuration file URL.

From the system execution space, view all contexts by entering the following command:

Command
Purpose

show context [name | detailcount]

Shows all contexts.

The detail option shows additional information. See the following sample outputs below for more information.

If you want to show information for a particular context, specify the name.

The count option shows the total number of contexts.


The following is sample output from the show context command. The following sample output shows three contexts:

hostname# show context
 
   
Context Name      Interfaces                    URL
*admin            GigabitEthernet0/1.100        disk0:/admin.cfg
                  GigabitEthernet0/1.101
contexta          GigabitEthernet0/1.200        disk0:/contexta.cfg
                  GigabitEthernet0/1.201
contextb          GigabitEthernet0/1.300        disk0:/contextb.cfg
                  GigabitEthernet0/1.301
Total active Security Contexts: 3
 
   

Table 6-2 shows each field description.

Table 6-2 show context Fields

Field
Description

Context Name

Lists all context names. The context name with the asterisk (*) is the admin context.

Interfaces

The interfaces assigned to the context.

URL

The URL from which the ASASM loads the context configuration.


The following is sample output from the show context detail command:

hostname# show context detail
 
   
Context "admin", has been created, but initial ACL rules not complete
  Config URL: disk0:/admin.cfg
  Real Interfaces: Management0/0
  Mapped Interfaces: Management0/0
  Flags: 0x00000013, ID: 1
 
   
Context "ctx", has been created, but initial ACL rules not complete
  Config URL: ctx.cfg
  Real Interfaces: GigabitEthernet0/0.10, GigabitEthernet0/1.20,
     GigabitEthernet0/2.30
  Mapped Interfaces: int1, int2, int3
  Flags: 0x00000011, ID: 2
 
   
Context "system", is a system resource
  Config URL: startup-config
  Real Interfaces:
  Mapped Interfaces: Control0/0, GigabitEthernet0/0,
     GigabitEthernet0/0.10, GigabitEthernet0/1, GigabitEthernet0/1.10,
     GigabitEthernet0/1.20, GigabitEthernet0/2, GigabitEthernet0/2.30,
     GigabitEthernet0/3, Management0/0, Management0/0.1
  Flags: 0x00000019, ID: 257
 
   
Context "null", is a system resource
  Config URL: ... null ...
  Real Interfaces:
  Mapped Interfaces:
  Flags: 0x00000009, ID: 258
 
   

See the command reference for more information about the detail output.

The following is sample output from the show context count command:

hostname# show context count
Total active contexts: 2

Viewing Resource Allocation

From the system execution space, you can view the allocation for each resource across all classes and class members.

To view the resource allocation, enter the following command:

Command
Purpose

show resource allocation [detail]

Shows the resource allocation. This command shows the resource allocation, but does not show the actual resources being used. See the "Viewing Resource Usage" section for more information about actual resource usage.

The detail argument shows additional information. See the following sample outputs for more information.


The following sample output shows the total allocation of each resource as an absolute value and as a percentage of the available system resources:

hostname# show resource allocation
Resource                    Total       % of Avail
 Conns [rate]               35000           N/A
 Inspects [rate]              35000           N/A
 Syslogs [rate]             10500           N/A
 Conns                     305000           30.50%
 Hosts                      78842           N/A
 SSH                           35           35.00%
 Telnet                        35           35.00%
 Xlates                     91749           N/A
 All                    unlimited 
 
   

Table 6-3 shows each field description.

Table 6-3 show resource allocation Fields

Field
Description

Resource

The name of the resource that you can limit.

Total

The total amount of the resource that is allocated across all contexts. The amount is an absolute number of concurrent instances or instances per second. If you specified a percentage in the class definition, the ASASM converts the percentage to an absolute number for this display.

% of Avail

The percentage of the total system resources that is allocated across all contexts, if the resource has a hard system limit. If a resource does not have a system limit, this column shows N/A.


The following is sample output from the show resource allocation detail command:

hostname# show resource allocation detail
Resource Origin:
    A    Value was derived from the resource 'all'
    C    Value set in the definition of this class
    D    Value set in default class
Resource         Class          Mmbrs  Origin      Limit      Total    Total %
Conns [rate]     default          all      CA  unlimited                     
                 gold               1       C      34000      34000     N/A
                 silver             1      CA      17000      17000     N/A
                 bronze             0      CA       8500                     
                 All Contexts:      3                         51000     N/A
 
   
Inspects [rate]  default          all      CA  unlimited                     
                 gold               1      DA  unlimited                     
                 silver             1      CA      10000      10000     N/A
                 bronze             0      CA       5000                     
                 All Contexts:      3                         10000     N/A
 
   
Syslogs [rate]   default          all      CA  unlimited                     
                 gold               1       C       6000       6000     N/A
                 silver             1      CA       3000       3000     N/A
                 bronze             0      CA       1500                     
                 All Contexts:      3                          9000     N/A
 
   
Conns            default          all      CA  unlimited                     
                 gold               1       C     200000     200000     20.00%
                 silver             1      CA     100000     100000     10.00%
                 bronze             0      CA      50000                     
                 All Contexts:      3                        300000     30.00%
 
   
Hosts            default          all      CA  unlimited                     
                 gold               1      DA  unlimited                     
                 silver             1      CA      26214      26214      N/A
                 bronze             0      CA      13107                     
                 All Contexts:      3                         26214      N/A
 
   
SSH              default          all       C          5                     
                 gold               1       D          5          5      5.00%
                 silver             1      CA         10         10     10.00%
                 bronze             0      CA          5                     
                 All Contexts:      3                            20     20.00%
 
   
Telnet           default          all       C          5                     
                 gold               1       D          5          5      5.00%
                 silver             1      CA         10         10     10.00%
                 bronze             0      CA          5                     
                 All Contexts:      3                            20     20.00%
 
   
Xlates           default          all      CA  unlimited                     
                 gold               1      DA  unlimited                     
                 silver             1      CA      23040      23040     N/A
                 bronze             0      CA      11520                     
                 All Contexts:      3                         23040     N/A
 
   
mac-addresses    default          all       C      65535                     
                 gold               1       D      65535      65535    100.00%
                 silver             1      CA       6553       6553      9.99%
                 bronze             0      CA       3276                     
                 All Contexts:      3                        137623    209.99%
 
   

Table 6-4 shows each field description.

Table 6-4 show resource allocation detail Fields

Field
Description

Resource

The name of the resource that you can limit.

Class

The name of each class, including the default class.

The All contexts field shows the total values across all classes.

Mmbrs

The number of contexts assigned to each class.

Origin

The origin of the resource limit, as follows:

A—You set this limit with the all option, instead of as an individual resource.

C—This limit is derived from the member class.

D—This limit was not defined in the member class, but was derived from the default class. For a context assigned to the default class, the value will be "C" instead of "D."

The ASASM can combine "A" with "C" or "D."

Limit

The limit of the resource per context, as an absolute number. If you specified a percentage in the class definition, the ASASM converts the percentage to an absolute number for this display.

Total

The total amount of the resource that is allocated across all contexts in the class. The amount is an absolute number of concurrent instances or instances per second. If the resource is unlimited, this display is blank.

% of Avail

The percentage of the total system resources that is allocated across all contexts in the class. If the resource is unlimited, this display is blank. If the resource does not have a system limit, then this column shows N/A.


Viewing Resource Usage

From the system execution space, you can view the resource usage for each context and display the system resource usage.

From the system execution space, view the resource usage for each context by entering the following command:

Command
Purpose

show resource usage [context context_name | top n | all | summary | system] [resource {resource_name | all} | detail] [counter counter_name [count_threshold]]

By default, all context usage is displayed; each context is listed separately.

Enter the top n keyword to show the contexts that are the top n users of the specified resource. You must specify a single resource type, and not resource all, with this option.

The summary option shows all context usage combined.

The system option shows all context usage combined, but shows the system limits for resources instead of the combined context limits.

For the resource resource_name, see Table 6-1 for available resource names. See also the show resource type command. Specify all (the default) for all types.

The detail option shows the resource usage of all resources, including those you cannot manage. For example, you can view the number of TCP intercepts.

The counter counter_name is one of the following keywords:

current—Shows the active concurrent instances or the current rate of the resource.

denied—Shows the number of instances that were denied because they exceeded the resource limit shown in the Limit column.

peak—Shows the peak concurrent instances, or the peak rate of the resource since the statistics were last cleared, either using the clear resource usage command or because the device rebooted.

all—(Default) Shows all statistics.

The count_threshold sets the number above which resources are shown. The default is 1. If the usage of the resource is below the number you set, then the resource is not shown. If you specify all for the counter name, then the count_threshold applies to the current usage.

Note To show all resources, set the count_threshold to 0.


The following is sample output from the show resource usage context command, which shows the resource usage for the admin context:

hostname# show resource usage context admin
 
   
Resource              Current         Peak      Limit    Denied  Context
Telnet                      1            1          5         0  admin
Conns                      44           55        N/A         0  admin
Hosts                      45           56        N/A         0  admin
 
   

The following is sample output from the show resource usage summary command, which shows the resource usage for all contexts and all resources. This sample shows the limits for 6 contexts.

hostname# show resource usage summary
 
   
Resource              Current         Peak      Limit     Denied Context
Syslogs [rate]           1743         2132      N/A            0 Summary
Conns                     584          763      280000(S)      0 Summary
Xlates                   8526         8966      N/A            0 Summary
Hosts                     254          254      N/A            0 Summary
Conns [rate]              270          535      N/A         1704 Summary
Inspects [rate]           270          535      N/A            0 Summary
S = System: Combined context limits exceed the system limit; the system limit is shown.
 
   

The following is sample output from the show resource usage summary command, which shows the limits for 25 contexts. Because the context limit for Telnet and SSH connections is 5 per context, then the combined limit is 125. The system limit is only 100, so the system limit is shown.

hostname# show resource usage summary
 
   
Resource              Current         Peak      Limit    Denied   Context
Telnet                      1            1        100[S]      0   Summary
SSH                         2            2        100[S]      0   Summary
Conns                      56           90        N/A         0   Summary
Hosts                      89          102        N/A         0   Summary
S = System: Combined context limits exceed the system limit; the system limit is shown.
 
   

The following is sample output from the show resource usage system command, which shows the resource usage for all contexts, but it shows the system limit instead of the combined context limits. The counter all 0 option is used to show resources that are not currently in use. The Denied statistics indicate how many times the resource was denied due to the system limit, if available.

hostname# show resource usage system counter all 0
 
   
Resource              Current         Peak      Limit        Denied    Context
Telnet                      0            0        100             0    System
SSH                         0            0        100             0    System
ASDM                        0            0         32             0    System
Syslogs [rate]              1           18        N/A             0    System
Conns                       0            1     280000             0    System
Xlates                      0            0        N/A             0    System
Hosts                       0            2        N/A             0    System
Conns [rate]                1            1        N/A             0    System
Inspects [rate]             0            0        N/A             0    System
 
   

Monitoring SYN Attacks in Contexts

The ASASM prevents SYN attacks using TCP Intercept. TCP Intercept uses the SYN cookies algorithm to prevent TCP SYN-flooding attacks. A SYN-flooding attack consists of a series of SYN packets usually originating from spoofed IP addresses. The constant flood of SYN packets keeps the server SYN queue full, which prevents it from servicing connection requests. When the embryonic connection threshold of a connection is crossed, the ASASM acts as a proxy for the server and generates a SYN-ACK response to the client SYN request. When the ASASM receives an ACK back from the client, it can then authenticate the client and allow the connection to the server.

Monitor SYN attacks using the following commands:

Command
Purpose

show perfmon

Monitors the rate of attacks for individual contexts.

show resource usage detail

Monitors the amount of resources being used by TCP intercept for individual contexts.

show resource usage summary detail

Monitors the resources being used by TCP intercept for the entire system.


The following is sample output from the show perfmon command that shows the rate of TCP intercepts for a context called admin.

hostname/admin# show perfmon
 
Context:admin
PERFMON STATS:   Current      Average
Xlates               0/s          0/s
Connections          0/s          0/s
TCP Conns            0/s          0/s
UDP Conns            0/s          0/s
URL Access           0/s          0/s
URL Server Req       0/s          0/s
WebSns Req           0/s          0/s
TCP Fixup            0/s          0/s
HTTP Fixup           0/s          0/s
FTP Fixup            0/s          0/s
AAA Authen           0/s          0/s
AAA Author           0/s          0/s
AAA Account          0/s          0/s
TCP Intercept    322779/s      322779/s
 
   

The following is sample output from the show resource usage detail command that shows the amount of resources being used by TCP Intercept for individual contexts. (Sample text in italics shows the TCP intercept information.)

hostname(config)# show resource usage detail        
Resource              Current         Peak      Limit        Denied Context
memory                 843732       847288  unlimited             0 admin
chunk:channels             14           15  unlimited             0 admin
chunk:fixup                15           15  unlimited             0 admin
chunk:hole                  1            1  unlimited             0 admin
chunk:ip-users             10           10  unlimited             0 admin
chunk:list-elem            21           21  unlimited             0 admin
chunk:list-hdr              3            4  unlimited             0 admin
chunk:route                 2            2  unlimited             0 admin
chunk:static                1            1  unlimited             0 admin
tcp-intercepts         328787       803610  unlimited             0 admin
np-statics                  3            3  unlimited             0 admin
statics                     1            1  unlimited             0 admin
ace-rules                   1            1  unlimited             0 admin
console-access-rul          2            2  unlimited             0 admin
fixup-rules                14           15  unlimited             0 admin
memory                 959872       960000  unlimited             0 c1
chunk:channels             15           16  unlimited             0 c1
chunk:dbgtrace              1            1  unlimited             0 c1
chunk:fixup                15           15  unlimited             0 c1
chunk:global                1            1  unlimited             0 c1
chunk:hole                  2            2  unlimited             0 c1
chunk:ip-users             10           10  unlimited             0 c1
chunk:udp-ctrl-blk          1            1  unlimited             0 c1
chunk:list-elem            24           24  unlimited             0 c1
chunk:list-hdr              5            6  unlimited             0 c1
chunk:nat                   1            1  unlimited             0 c1
chunk:route                 2            2  unlimited             0 c1
chunk:static                1            1  unlimited             0 c1
tcp-intercept-rate      16056        16254  unlimited             0 c1
globals                     1            1  unlimited             0 c1
np-statics                  3            3  unlimited             0 c1
statics                     1            1  unlimited             0 c1
nats                        1            1  unlimited             0 c1
ace-rules                   2            2  unlimited             0 c1
console-access-rul          2            2  unlimited             0 c1
fixup-rules                14           15  unlimited             0 c1
memory              232695716    232020648  unlimited             0 system
chunk:channels             17           20  unlimited             0 system
chunk:dbgtrace              3            3  unlimited             0 system
chunk:fixup                15           15  unlimited             0 system
chunk:ip-users              4            4  unlimited             0 system
chunk:list-elem          1014         1014  unlimited             0 system
chunk:list-hdr              1            1  unlimited             0 system
chunk:route                 1            1  unlimited             0 system
block:16384               510          885  unlimited             0 system
block:2048                 32           34  unlimited             0 system
 
   

The following sample output shows the resources being used by TCP intercept for the entire system. (Sample text in italics shows the TCP intercept information.)

hostname(config)# show resource usage summary detail
Resource              Current         Peak      Limit        Denied Context
memory              238421312    238434336  unlimited             0 Summary
chunk:channels             46           48  unlimited             0 Summary
chunk:dbgtrace              4            4  unlimited             0 Summary
chunk:fixup                45           45  unlimited             0 Summary
chunk:global                1            1  unlimited             0 Summary
chunk:hole                  3            3  unlimited             0 Summary
chunk:ip-users             24           24  unlimited             0 Summary
chunk:udp-ctrl-blk          1            1  unlimited             0 Summary
chunk:list-elem          1059         1059  unlimited             0 Summary
chunk:list-hdr             10           11  unlimited             0 Summary
chunk:nat                   1            1  unlimited             0 Summary
chunk:route                 5            5  unlimited             0 Summary
chunk:static                2            2  unlimited             0 Summary
block:16384               510          885  unlimited             0 Summary
block:2048                 32           35  unlimited             0 Summary
tcp-intercept-rate     341306       811579  unlimited             0 Summary
globals                     1            1  unlimited             0 Summary
np-statics                  6            6  unlimited             0 Summary
statics                     2            2        N/A             0 Summary
nats                        1            1        N/A             0 Summary
ace-rules                   3            3        N/A             0 Summary
console-access-rul          4            4        N/A             0 Summary
fixup-rules                43           44        N/A             0 Summary

Viewing Assigned MAC Addresses

You can view auto-generated MAC addresses within the system configuration or within the context. This section includes the following topics:

Viewing MAC Addresses in the System Configuration

Viewing MAC Addresses Within a Context

Viewing MAC Addresses in the System Configuration

This section describes how to view MAC addresses in the system configuration.

Guidelines

If you manually assign a MAC address to an interface, but also have auto-generation enabled, the auto-generated address continues to show in the configuration even though the manual MAC address is the one that is in use. If you later remove the manual MAC address, the auto-generated one shown will be used.

Detailed Steps

Command
Purpose

show running-config all context [name]

Shows the assigned MAC addresses from the system execution space.

The all option is required to view the assigned MAC addresses. Although this command is user-configurable in global configuration mode only, the mac-address auto command appears as a read-only entry in the configuration for each context along with the assigned MAC address. Only allocated interfaces that are configured with a nameif command within the context have a MAC address assigned.


Examples

The following output from the show running-config all context admin command shows the primary and standby MAC address assigned to the Management0/0 interface:

hostname# show running-config all context admin
 
   
context admin
  allocate-interface Management0/0
  mac-address auto Management0/0 a24d.0000.1440 a24d.0000.1441
  config-url disk0:/admin.cfg
 
   

The following output from the show running-config all context command shows all the MAC addresses (primary and standby) for all context interfaces. Note that because the GigabitEthernet0/0 and GigabitEthernet0/1 main interfaces are not configured with a nameif command inside the contexts, no MAC addresses have been generated for them.

 
   
hostname# show running-config all context
 
   
admin-context admin
context admin
  allocate-interface Management0/0 
  mac-address auto Management0/0 a2d2.0400.125a a2d2.0400.125b
  config-url disk0:/admin.cfg
!
 
   
context CTX1
  allocate-interface GigabitEthernet0/0 
  allocate-interface GigabitEthernet0/0.1-GigabitEthernet0/0.5 
  mac-address auto GigabitEthernet0/0.1 a2d2.0400.11bc a2d2.0400.11bd
  mac-address auto GigabitEthernet0/0.2 a2d2.0400.11c0 a2d2.0400.11c1
  mac-address auto GigabitEthernet0/0.3 a2d2.0400.11c4 a2d2.0400.11c5
  mac-address auto GigabitEthernet0/0.4 a2d2.0400.11c8 a2d2.0400.11c9
  mac-address auto GigabitEthernet0/0.5 a2d2.0400.11cc a2d2.0400.11cd
  allocate-interface GigabitEthernet0/1 
  allocate-interface GigabitEthernet0/1.1-GigabitEthernet0/1.3 
  mac-address auto GigabitEthernet0/1.1 a2d2.0400.120c a2d2.0400.120d
  mac-address auto GigabitEthernet0/1.2 a2d2.0400.1210 a2d2.0400.1211
  mac-address auto GigabitEthernet0/1.3 a2d2.0400.1214 a2d2.0400.1215
  config-url disk0:/CTX1.cfg
!
 
   
context CTX2
  allocate-interface GigabitEthernet0/0 
  allocate-interface GigabitEthernet0/0.1-GigabitEthernet0/0.5 
  mac-address auto GigabitEthernet0/0.1 a2d2.0400.11ba a2d2.0400.11bb
  mac-address auto GigabitEthernet0/0.2 a2d2.0400.11be a2d2.0400.11bf
  mac-address auto GigabitEthernet0/0.3 a2d2.0400.11c2 a2d2.0400.11c3
  mac-address auto GigabitEthernet0/0.4 a2d2.0400.11c6 a2d2.0400.11c7
  mac-address auto GigabitEthernet0/0.5 a2d2.0400.11ca a2d2.0400.11cb
  allocate-interface GigabitEthernet0/1 
  allocate-interface GigabitEthernet0/1.1-GigabitEthernet0/1.3 
  mac-address auto GigabitEthernet0/1.1 a2d2.0400.120a a2d2.0400.120b
  mac-address auto GigabitEthernet0/1.2 a2d2.0400.120e a2d2.0400.120f
  mac-address auto GigabitEthernet0/1.3 a2d2.0400.1212 a2d2.0400.1213
  config-url disk0:/CTX2.cfg
!

Viewing MAC Addresses Within a Context

This section describes how to view MAC addresses within a context.

Detailed Steps

Command
Purpose

show interface | include (Interface)|(MAC)

Shows the MAC address in use by each interface within the context.


Examples

For example:

hostname/context# show interface | include (Interface)|(MAC)
 
   
Interface GigabitEthernet1/1.1 "g1/1.1", is down, line protocol is down
        MAC address a201.0101.0600, MTU 1500
Interface GigabitEthernet1/1.2 "g1/1.2", is down, line protocol is down
        MAC address a201.0102.0600, MTU 1500
Interface GigabitEthernet1/1.3 "g1/1.3", is down, line protocol is down
        MAC address a201.0103.0600, MTU 1500
...
 
   

Note The show interface command shows the MAC address in use; if you manually assign a MAC address and also have auto-generation enabled, then you can only view the unused auto-generated address from within the system configuration.


Configuration Examples for Multiple Context Mode

The following example:

Automatically sets the MAC addresses in contexts.

Sets the default class limit for conns to 10 percent instead of unlimited.

Creates a gold resource class.

Sets the admin context to be "administrator."

Creates a context called "administrator" on the internal flash memory to be part of the default resource class.

Adds two contexts from an FTP server as part of the gold resource class.

hostname(config)# mac-address auto prefix 19

hostname(config)# class default
hostname(config-class)# limit-resource conns 10%
 
   
hostname(config)# class gold
hostname(config-class)# limit-resource mac-addresses 10000
hostname(config-class)# limit-resource conns 15%
hostname(config-class)# limit-resource rate conns 1000
hostname(config-class)# limit-resource rate inspects 500
hostname(config-class)# limit-resource hosts 9000
hostname(config-class)# limit-resource asdm 5
hostname(config-class)# limit-resource ssh 5
hostname(config-class)# limit-resource rate syslogs 5000
hostname(config-class)# limit-resource telnet 5
hostname(config-class)# limit-resource xlates 36000
 
   
hostname(config)# admin-context administrator
hostname(config)# context administrator
hostname(config-ctx)# allocate-interface gigabitethernet0/0.1
hostname(config-ctx)# allocate-interface gigabitethernet0/1.1
hostname(config-ctx)# config-url flash:/admin.cfg
 
   
hostname(config-ctx)# context test
hostname(config-ctx)# allocate-interface gigabitethernet0/0.100 int1
hostname(config-ctx)# allocate-interface gigabitethernet0/0.102 int2
hostname(config-ctx)# allocate-interface gigabitethernet0/0.110-gigabitethernet0/0.115 
int3-int8
hostname(config-ctx)# config-url ftp://user1:passw0rd@10.1.1.1/configlets/test.cfg
hostname(config-ctx)# member gold
 
   
hostname(config-ctx)# context sample
hostname(config-ctx)# allocate-interface gigabitethernet0/1.200 int1
hostname(config-ctx)# allocate-interface gigabitethernet0/1.212 int2
hostname(config-ctx)# allocate-interface gigabitethernet0/1.230-gigabitethernet0/1.235 
int3-int8
hostname(config-ctx)# config-url ftp://user1:passw0rd@10.1.1.1/configlets/sample.cfg
hostname(config-ctx)# member gold
 
   

Feature History for Multiple Context Mode

Table 6-5 lists each feature change and the platform release in which it was implemented.

Table 6-5 Feature History for Multiple Context Mode 

Feature Name
Platform Releases
Feature Information

Multiple security contexts

7.0(1)

Multiple context mode was introduced.

We introduced the following commands: context, mode, and class.

 

Automatic MAC address assignment

7.2(1)

Automatic assignment of MAC address to context interfaces was introduced.

We introduced the following command: mac-address auto.

 

Resource management

7.2(1)

Resource management was introduced.

We introduced the following commands: class, limit-resource, and member.

 

Virtual sensors for IPS

8.0(2)

The AIP SSM running IPS software Version 6.0 and above can run multiple virtual sensors, which means you can configure multiple security policies on the AIP SSM. You can assign each context or single mode ASASM to one or more virtual sensors, or you can assign multiple security contexts to the same virtual sensor.

We introduced the following command: allocate-ips.

 

Automatic MAC address assignment enhancements

8.0(5)/8.2(2)

The MAC address format was changed to use a prefix, to use a fixed starting value (A2), and to use a different scheme for the primary and secondary unit MAC addresses in a failover pair. The MAC addresses are also now persistent across reloads. The command parser now checks if auto-generation is enabled; if you want to also manually assign a MAC address, you cannot start the manual MAC address with A2.

We modified the following command: mac-address auto prefix.

 

Maximum contexts increased for the ASA 5550 and 5580

8.4(1)

The maximum security contexts for the ASA 5550 was increased from 50 to 100. The maximum for the ASA 5580 was increased from 50 to 250.

Automatic MAC address assignment enabled by default

8.5(1)

Automatic MAC address assignment is now enabled by default.

We modified the following command: mac-address auto.

 

Automatic generation of a MAC address prefix for the mac-address auto command

8.6(1)

In multiple context mode, the ASASM now converts the automatic MAC address generation configuration to use a default prefix. The ASASM auto-generates the prefix based on the last two bytes of the interface MAC address. This conversion happens automatically when you reload, or if you reenable MAC address generation. The prefix method of generation provides many benefits, including a better guarantee of unique MAC addresses on a segment. You can view the auto-generated prefix by entering the show running-config mac-address command. If you want to change the prefix, you can reconfigure the feature with a custom prefix. The legacy method of MAC address generation is no longer available.

Note To maintain hitless upgrade for failover pairs, the ASASM does not convert the MAC address method in an existing configuration upon a reload if failover is enabled. However, we strongly recommend that you manually change to the prefix method of generation when using failover. After upgrading, to use the prefix method of MAC address generation, reenable MAC address generation to use the default prefix.

We modified the following command: mac-address auto.