Cisco Nexus 7000 Series NX-OS SAN Switching Configuration Guide
Configuring FC-SP and DHCHAP
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Configuring FC-SP and DHCHAP

Configuring FC-SP and DHCHAP

This chapter contains the following sections:

Configuring FC-SP and DHCHAP

Fibre Channel Security Protocol (FC-SP) capabilities provide switch-to-switch and host-to-switch authentication to overcome security challenges for enterprise-wide fabrics. Diffie-Hellman Challenge Handshake Authentication Protocol (DHCHAP) is an FC-SP protocol that provides authentication between Cisco SAN switches and other devices. DHCHAP consists of the CHAP protocol combined with the Diffie-Hellman exchange.

Information About Fabric Authentication

All Cisco SAN switches enable fabric-wide authentication from one switch to another switch, or from a switch to a host. These switch and host authentications are performed locally or remotely in each fabric. As storage islands are consolidated and migrated to enterprise-wide fabrics, new security challenges arise. The approach of securing storage islands cannot always be guaranteed in enterprise-wide fabrics. For example, in a campus environment with geographically distributed switches, someone could maliciously interconnect incompatible switches or you could accidentally do so, resulting in Inter-Switch Link (ISL) isolation and link disruption.

Cisco SAN switches support authentication features to address physical security (see the following figure).

Figure 1. Switch and Host Authentication


Note


Fibre Channel Host Bus Adapters (HBAs) with appropriate firmware and drivers are required for host-switch authentication.


DHCHAP

DHCHAP is an authentication protocol that authenticates the devices connecting to a switch. Fibre Channel authentication allows only trusted devices to be added to a fabric, which prevents unauthorized devices from accessing the switch.


Note


The terms FC-SP and DHCHAP are used interchangeably in this chapter.


DHCHAP is a mandatory password-based, key-exchange authentication protocol that supports both switch-to-switch and host-to-switch authentication. DHCHAP negotiates hash algorithms and DH groups before performing authentication. It supports MD5 and SHA-1 algorithm-based authentication.

To configure DHCHAP authentication using the local password database, perform this task:

SUMMARY STEPS

1.    Enable DHCHAP.

2.    Identify and configure the DHCHAP authentication modes.

3.    Configure the hash algorithm and DH group.

4.    Configure the DHCHAP password for the local switch and other switches in the fabric.

5.    Configure the DHCHAP timeout value for reauthentication.

6.    Verify the DHCHAP configuration.


DETAILED STEPS
Step 1   Enable DHCHAP.
Step 2   Identify and configure the DHCHAP authentication modes.
Step 3   Configure the hash algorithm and DH group.
Step 4   Configure the DHCHAP password for the local switch and other switches in the fabric.
Step 5   Configure the DHCHAP timeout value for reauthentication.
Step 6   Verify the DHCHAP configuration.

DHCHAP Compatibility with Fibre Channel Features

This section identifies the impact of configuring the DHCHAP feature along with existing Cisco NX-OS features:


  • SAN port channel interfaces—If DHCHAP is enabled for ports belonging to a SAN port channel, DHCHAP authentication is performed at the physical interface level, not at the port channel level.

  • Port security or fabric binding—Fabric-binding policies are enforced based on identities authenticated by DHCHAP.

  • VSANs—DHCHAP authentication is not done on a per-VSAN basis.

About Enabling DHCHAP

By default, the DHCHAP feature is disabled in all Cisco SAN switches.

You must explicitly enable the DHCHAP feature to access the configuration and verification commands for fabric authentication. When you disable this feature, all related configurations are automatically discarded.

Enabling DHCHAP

To enable DHCHAP, perform this task:

SUMMARY STEPS

1.    switch# configuration terminal

2.    switch(config)# feature fcsp

3.    switch(config)# no feature fcsp


DETAILED STEPS
  Command or Action Purpose
Step 1 switch# configuration terminal
 

Enters configuration mode.

 
Step 2 switch(config)# feature fcsp
 

Enables the DHCHAP in this switch.

 
Step 3 switch(config)# no feature fcsp
 

Disables (default) the DHCHAP in this switch.

 

About DHCHAP Authentication Modes

The DHCHAP authentication status for each interface depends on the configured DHCHAP port mode.

When the DHCHAP feature is enabled in a switch, each Fibre Channel interface or FCIP interface may be configured to be in one of four DHCHAP port modes:


  • On—During switch initialization, if the connecting device supports DHCHAP authentication, the software performs the authentication sequence. If the connecting device does not support DHCHAP authentication, the link is placed in an isolated state.

  • Auto-Active—During switch initialization, if the connecting device supports DHCHAP authentication, the software performs the authentication sequence. If the connecting device does not support DHCHAP authentication, the software continues with the rest of the initialization sequence.

  • Auto-Passive (default)—The switch does not initiate DHCHAP authentication, but participates in DHCHAP authentication if the connecting device initiates DHCHAP authentication.

  • Off—The switch does not support DHCHAP authentication. Authentication messages sent to ports in this mode return error messages to the initiating switch.


Note


Whenever DHCHAP port mode is changed to a mode other than the Off mode, reauthentication is performed.


The following table identifies switch-to-switch authentication between two Cisco switches in various modes.

Table 1 DHCHAP Authentication Status Between Two SAN Switches

Switch N DHCHAP Modes

Switch 1 DHCHAP Modes

on

auto-active

auto-passive

off

on

FC-SP authentication is performed.

FC-SP authentication is performed.

FC-SP authentication is performed.

Link is brought down.

auto-Active

FC-SP authentication is not performed.

auto-Passive

FC-SP authentication is not performed.

off

Link is brought down.

FC-SP authentication is not performed.

Configuring the DHCHAP Mode

To configure the DHCHAP mode for a particular interface, perform this task:

SUMMARY STEPS

1.    switch# configuration terminal

2.    switch(config)# interface vfc if-number - if-number

3.    switch(config-if)# fcsp on

4.    switch(config-if)# fcsp off

5.    switch(config-if)# fcsp auto-active timeout-period

6.    switch(config-if)# fcsp auto-passive


DETAILED STEPS
  Command or Action Purpose
Step 1 switch# configuration terminal
 

Enters configuration mode.

 
Step 2 switch(config)# interface vfc if-number - if-number
 

Selects a range of interfaces and enters the interface configuration mode.

 
Step 3 switch(config-if)# fcsp on
 

Sets the DHCHAP mode for the selected interfaces to be in the on state.

 
Step 4 switch(config-if)# fcsp off
 

Reverts to the factory default of auto-passive for these three interfaces.

 
Step 5 switch(config-if)# fcsp auto-active timeout-period
 

Changes the DHCHAP authentication mode to auto-active for the selected interfaces. The timeout period value (in minutes) sets how often reauthentication occurs after the initial authentication. Zero (0) indicates that the port does not perform reauthentication.

 
Step 6 switch(config-if)# fcsp auto-passive
 

Changes the DHCHAP authentication mode to auto-passive for the selected interfaces. Reauthentication is disabled (default).

 

About the DHCHAP Hash Algorithm

Cisco SAN switches support a default hash algorithm priority list of MD5 followed by SHA-1 for DHCHAP authentication.

If you change the hash algorithm configuration, then change it globally for all switches in the fabric.


Caution


RADIUS and TACACS+ protocols always use MD5 for CHAP authentication. Using SHA-1 as the hash algorithm may prevent RADIUS and TACACS+ usage, even if these AAA protocols are enabled for DHCHAP authentication.


Configuring the DHCHAP Hash Algorithm

To configure the hash algorithm, perform this task:

SUMMARY STEPS

1.    switch# configuration terminal

2.    switch(config)# fcsp dhchap hash [md5] [sha1]

3.    switch(config)# no fcsp dhchap hash sha1


DETAILED STEPS
  Command or Action Purpose
Step 1 switch# configuration terminal
 

Enters configuration mode.

 
Step 2 switch(config)# fcsp dhchap hash [md5] [sha1]
 

Configures the use of the the MD5 or SHA-1 hash algorithm.

 
Step 3 switch(config)# no fcsp dhchap hash sha1
 

Reverts to the factory default priority list of the MD5 hash algorithm followed by the SHA-1 hash algorithm.

 

About the DHCHAP Group Settings

All Cisco SAN switches support all DHCHAP groups specified in the standard: 0 (null DH group, which does not perform the Diffie-Hellman exchange), 1, 2, 3, or 4.

If you change the DH group configuration, change it globally for all switches in the fabric.

Configuring the DHCHAP Group Settings

To change the DH group settings, perform this task:

SUMMARY STEPS

1.    switch# configuration terminal

2.    switch(config)# fcsp dhchap dhgroup [0 | 1 | 2 | 3 | 4]

3.    switch(config)# no fcsp dhchap dhgroup [0 | 1 | 2| 3 | 4]


DETAILED STEPS
  Command or Action Purpose
Step 1 switch# configuration terminal
 

Enters configuration mode.

 
Step 2 switch(config)# fcsp dhchap dhgroup [0 | 1 | 2 | 3 | 4]
 

Prioritizes the use of DH groups in the configured order.

 
Step 3 switch(config)# no fcsp dhchap dhgroup [0 | 1 | 2| 3 | 4]
 

Reverts to the DHCHAP factory default order of 0, 4, 1, 2, and 3.

 

About the DHCHAP Password

DHCHAP authentication in each direction requires a shared secret password between the connected devices. To do this, you can use one of three configurations to manage passwords for all switches in the fabric that participate in DHCHAP:


  • Configuration 1—Use the same password for all switches in the fabric. This is the simplest configuration. When you add a new switch, you use the same password to authenticate that switch in this fabric. It is also the most vulnerable configuration if someone from the outside maliciously attempts to access any one switch in the fabric.

  • Configuration 2—Use a different password for each switch and maintain that password list in each switch in the fabric. When you add a new switch, you create a new password list and update all switches with the new list. Accessing one switch yields the password list for all switches in that fabric.

  • Configuration 3—Use different passwords for different switches in the fabric. When you add a new switch, multiple new passwords corresponding to each switch in the fabric must be generated and configured in each switch. Even if one switch is compromised, the password of other switches are still protected. This configuration requires considerable password maintenance by the user.


Note


All passwords are restricted to 64 alphanumeric characters and can be changed, but not deleted.


We recommend using RADIUS or TACACS+ for fabrics with more than five switches. If you need to use a local password database, you can continue to do so using Configuration 3 and using the Cisco DCNM for SAN to manage the password database.

Configuring DHCHAP Passwords for the Local Switch

To configure the DHCHAP password for the local switch, perform this task:

SUMMARY STEPS

1.    switch# configuration terminal

2.    switch(config)# fcsp dhchap password [0 | 7] password [wwn wwn-id]


DETAILED STEPS
  Command or Action Purpose
Step 1 switch# configuration terminal
 

Enters configuration mode.

 
Step 2 switch(config)# fcsp dhchap password [0 | 7] password [wwn wwn-id]
 

Configures a clear text password for the local switch.

 

About Password Configuration for Remote Devices

You can configure passwords in the local authentication database for other devices in a fabric. The other devices are identified by their device name, which is also known as the switch WWN or device WWN. The password is restricted to 64 characters and can be specified in clear text (0) or in encrypted text (7).


Note


The switch WWN identifies the physical switch. This WWN is used to authenticate the switch and is different from the VSAN node WWN.


Configuring DHCHAP Passwords for Remote Devices

To locally configure the remote DHCHAP password for another switch in the fabric, perform this task:

SUMMARY STEPS

1.    switch# configuration terminal

2.    switch(config)# fcsp dhchap devicename switch-wwn password password

3.    switch(config)# no fcsp dhchap devicename switch-wwn password password


DETAILED STEPS
  Command or Action Purpose
Step 1 switch# configuration terminal
 

Enters configuration mode.

 
Step 2 switch(config)# fcsp dhchap devicename switch-wwn password password
 

Configures a password for another switch in the fabric that is identified by the switch WWN device name.

 
Step 3 switch(config)# no fcsp dhchap devicename switch-wwn password password
 

Removes the password entry for this switch from the local authentication database.

 

About the DHCHAP Timeout Value

During the DHCHAP protocol exchange, if the switch does not receive the expected DHCHAP message within a specified time interval, authentication failure is assumed. The time ranges from 20 (no authentication is performed) to 1000 seconds. The default is 30 seconds.

When changing the timeout value, consider the following factors:


  • The existing RADIUS and TACACS+ timeout values.

  • The same value must also be configured on all switches in the fabric.

Configuring the DHCHAP Timeout Value

To configure the DHCHAP timeout value, perform this task:

SUMMARY STEPS

1.    switch# configuration terminal

2.    switch(config)# fcsp timeout timeout

3.    switch(config)# no fcsp timeout timeout


DETAILED STEPS
  Command or Action Purpose
Step 1 switch# configuration terminal
 

Enters configuration mode.

 
Step 2 switch(config)# fcsp timeout timeout
 

Configures the reauthentication timeout to the specified value. The unit is seconds.

 
Step 3 switch(config)# no fcsp timeout timeout
 

Reverts to the factory default of 30 seconds.

 

Configuring DHCHAP AAA Authentication

You can configure AAA authentication to use a RADIUS or TACACS+ server group. If AAA authentication is not configured, local authentication is used by default.

Sample Configuration

To configure the authentication setup, perform this task:

SUMMARY STEPS

1.    Obtain the device name of the Cisco SAN switch in the fabric. The Cisco SAN switch in the fabric is identified by the switch WWN.

2.    Explicitly enable DHCHAP in this switch.

3.    Configure a clear text password for this switch. This password will be used by the connecting device.

4.    Configure a password for another switch in the fabric that is identified by the switch WWN device name.

5.    Enable the DHCHAP mode for the required interface.

6.    Verify the protocol security information configured in this switch by displaying the DHCHAP local password database.

7.    Display the DHCHAP configuration in the interface.

8.    Repeat these steps on the connecting switch.


DETAILED STEPS
Step 1   Obtain the device name of the Cisco SAN switch in the fabric. The Cisco SAN switch in the fabric is identified by the switch WWN.

Example:
switch# show wwn switch
Switch WWN is 20:00:00:05:30:00:54:de
Step 2   Explicitly enable DHCHAP in this switch.
Note   

When you disable DHCHAP, all related configurations are automatically discarded.



Example:
switch(config)# feature fcsp

Step 3   Configure a clear text password for this switch. This password will be used by the connecting device.

Example:
 switch(config)# fcsp dhchap password rtp9216
Step 4   Configure a password for another switch in the fabric that is identified by the switch WWN device name.

Example:
switch(config)# fcsp dhchap devicename 20:00:00:05:30:00:38:5e password rtp9509
Step 5   Enable the DHCHAP mode for the required interface.
Note   

Whenever DHCHAP port mode is changed to a mode other than the Off mode, reauthentication is performed.



Example:
switch(config)# interface vfc 2
switch(config-if)# fcsp on
Step 6   Verify the protocol security information configured in this switch by displaying the DHCHAP local password database.

Example:
switch# show fcsp dhchap database
DHCHAP Local Password:
        Non-device specific password:*******
Other Devices' Passwords:
        Password for device with WWN:20:00:00:05:30:00:38:5e is *******
Step 7   Display the DHCHAP configuration in the interface.

Example:
switch# show fcsp interface vfc 2
vfc 2
        fcsp authentication mode:SEC_MODE_ON
        Status:Successfully authenticated
Step 8   Repeat these steps on the connecting switch.

Example:
MDS-9509# show wwn switch
Switch WWN is 20:00:00:05:30:00:38:5e
MDS-9509(config)# fcsp enable
MDS-9509(config)# fcsp dhchap password rtp9509
MDS-9509(config)# fcsp dhchap devicename 20:00:00:05:30:00:54:de password rtp9216
MDS-9509(config)# interface fc 4/5
MDS-9509(config-if)# fcsp on
MDS-9509# show fcsp dhchap database
DHCHAP Local Password:
        Non-device specific password:*******
Other Devices' Passwords:
        Password for device with WWN:20:00:00:05:30:00:54:de is *******
MDS-9509# show fcsp interface fc2/4
Fc2/4
        fcsp authentication mode:SEC_MODE_ON
        Status:Successfully authenticated
You have now enabled and configured DHCHAP authentication for the sample setup.

Default Fabric Security Settings

The following table lists the default settings for all fabric security features in any switch.

Table 2  Default Fabric Security Settings

Parameters

Default

DHCHAP feature

Disabled

DHCHAP hash algorithm

A priority list of MD5 followed by SHA-1 for DHCHAP authentication

DHCHAP authentication mode

Auto-passive

DHCHAP group default priority exchange order

0, 4, 1, 2, and 3, respectively

DHCHAP timeout value

30 seconds