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Example: Configuring BFD Authentication for OSPF

BFD Authentication for OSPF Overview

Bidirectional Forwarding Detection (BFD) enables rapid detection of communication failures between adjacent systems. By default, authentication for BFD sessions is disabled. However, when you run BFD over Network Layer protocols, the risk of service attacks can be significant. We strongly recommend using authentication if you are running BFD over multiple hops or through insecure tunnels. Beginning with Junos OS Release 9.6, Junos OS supports authentication for BFD sessions running over OSPFv2. BFD authentication is not supported on MPLS OAM sessions. BFD authentication is only supported in the Canada and United States version of the Junos OS image and is not available in the export version.

You authenticate BFD sessions by specifying an authentication algorithm and keychain, and then associating that configuration information with a security authentication keychain using the keychain name.

The following sections describe the supported authentication algorithms, security keychains, and level of authentication that can be configured:

• BFD Authentication Algorithms
• Security Authentication Keychains
• Strict Versus Loose Authentication

BFD Authentication Algorithms

• simple-password—Plain-text password. One to 16 bytes of plain text are used to authenticate the BFD session. One or more passwords can be configured. This method is the least secure and should be used only when BFD sessions are not subject to packet interception.
• keyed-md5—Keyed Message Digest 5 hash algorithm for sessions with transmit and receive intervals greater than 100 ms. To authenticate the BFD session, keyed MD5 uses one or more secret keys (generated by the algorithm) and a sequence number that is updated periodically. With this method, packets are accepted at the receiving end of the session if one of the keys matches and the sequence number is greater than or equal to the last sequence number received. Although more secure than a simple password, this method is vulnerable to replay attacks. Increasing the rate at which the sequence number is updated can reduce this risk.
• meticulous-keyed-md5—Meticulous keyed Message Digest 5 hash algorithm. This method works in the same manner as keyed MD5, but the sequence number is updated with every packet. Although more secure than keyed MD5 and simple passwords, this method might take additional time to authenticate the session.
• keyed-sha-1—Keyed Secure Hash Algorithm I for sessions with transmit and receive intervals greater than 100 ms. To authenticate the BFD session, keyed SHA uses one or more secret keys (generated by the algorithm) and a sequence number that is updated periodically. The key is not carried within the packets. With this method, packets are accepted at the receiving end of the session if one of the keys matches and the sequence number is greater than the last sequence number received.
• meticulous-keyed-sha-1—Meticulous keyed Secure Hash Algorithm I. This method works in the same manner as keyed SHA, but the sequence number is updated with every packet. Although more secure than keyed SHA and simple passwords, this method might take additional time to authenticate the session.

Note: Nonstop active routing (NSR) is not supported with the meticulous-keyed-md5 and meticulous-keyed-sha-1 authentication algorithms. BFD sessions using these algorithms might go down after a switchover.

Security Authentication Keychains

The security authentication keychain defines the authentication attributes used for authentication key updates. When the security authentication keychain is configured and associated with a protocol through the keychain name, authentication key updates can occur without interrupting routing and signaling protocols.

The authentication keychain contains one or more keychains. Each keychain contains one or more keys. Each key holds the secret data and the time at which the key becomes valid. The algorithm and keychain must be configured on both ends of the BFD session, and they must match. Any mismatch in configuration prevents the BFD session from being created.

BFD allows multiple clients per session, and each client can have its own keychain and algorithm defined. To avoid confusion, we recommend specifying only one security authentication keychain.

Strict Versus Loose Authentication

By default, strict authentication is enabled and authentication is checked at both ends of each BFD session. Optionally, to smooth migration from nonauthenticated sessions to authenticated sessions, you can configure loose checking. When loose checking is configured, packets are accepted without authentication being checked at each end of the session. This feature is intended for transitional periods only.

Configuring BFD Authentication for OSPF

Beginning with Junos OS Release 9.6, you can configure authentication for BFD sessions running over OSPFv2. Routing instances are also supported.

The following sections provide instructions for configuring and viewing BFD authentication on OSPF:

• Configuring BFD Authentication Parameters
• Viewing Authentication Information for BFD Sessions

Configuring BFD Authentication Parameters

Only three steps are needed to configure authentication on a BFD session:

1. Specify the BFD authentication algorithm for the OSPFv2 protocol.
2. Associate the authentication keychain with the OSPFv2 protocol.
3. Configure the related security authentication keychain.

1. Specify the algorithm (keyed-md5, keyed-sha-1, meticulous-keyed-md5, meticulous-keyed-sha-1, or simple-password) to use for BFD authentication on an OSPF route or routing instance.
   [edit]user@host# set protocols ospf area 0.0.0.1 interface if2-ospf bfd-liveness-detection authentication algorithm keyed-sha-1

   Note: Nonstop active routing (NSR) is not supported with meticulous-keyed-md5 and meticulous-keyed-sha-1 authentication algorithms. BFD sessions using these algorithms might go down after a switchover.

2. Specify the keychain to be used to associate BFD sessions on the specified OSPF route or routing instance with the unique security authentication keychain attributes.

   This keychain should match the keychain name configured at the [edit security authentication key-chains] hierarchy level.

   [edit]user@host# set protocols ospf area 0.0.0.1 interface if2-ospf bfd-liveness-detection authentication keychain bfd-ospf

   Note: The algorithm and keychain must be configured on both ends of the BFD session, and they must match. Any mismatch in configuration prevents the BFD session from being created.

3. Specify the unique security authentication information for BFD sessions:
   • The matching keychain name as specified in Step 2.
   • At least one key, a unique integer between 0 and 63. Creating multiple keys enables multiple clients to use the BFD session.
   • The secret data used to allow access to the session.
   • The time at which the authentication key becomes active, in the format yyyy-mm-dd.hh:mm:ss.
   [edit security]user@host# authentication-key-chains key-chain bfd-ospf key 53 secret $9$ggaJDmPQ6/tJgF/AtREVsyPsnCtUHm start-time 2009-06-14.10:00:00
4. (Optional) Specify loose authentication checking if you are transitioning from nonauthenticated sessions to authenticated sessions.
   [edit]user@host> set protocols ospf interface if2-ospf bfd-liveness-detection authentication loose-check
5. (Optional) View your configuration using the show bfd session detail or show bfd session extensive command.
6. Repeat the steps in this procedure to configure the other end of the BFD session.

Note: BFD authentication is only supported in the Canada and United States version of the Junos OS image and is not available in the export version.

Viewing Authentication Information for BFD Sessions

You can view the existing BFD authentication configuration using the show bfd session detail and show bfd session extensive commands.

The following example shows BFD authentication configured for the if2-ospf BGP group. It specifies the keyed SHA-1 authentication algorithm and a keychain name of bfd-ospf. The authentication keychain is configured with two keys. Key 1 contains the secret data “$9$ggaJDmPQ6/tJgF/AtREVsyPsnCtUHm” and a start time of June 1, 2009, at 9:46:02 AM PST. Key 2 contains the secret data “$9$a5jiKW9l.reP38ny.TszF2/9” and a start time of June 1, 2009, at 3:29:20 PM PST.

If you commit these updates to your configuration, you see output similar to the following. In the output for the show bfd session detail command, Authenticate is displayed to indicate that BFD authentication is configured.

user@host# show bfd session detail 

                                                  Detect   Transmit
Address                  State     Interface      Time     Interval  Multiplier
10.9.1.33            Up        so-7/1/0.0          0.600     0.200      3
  Client OSPF, TX interval 0.200, RX interval 0.200, multiplier 3, Authenticate
  Session up time 3d 00:34
  Local diagnostic None, remote diagnostic None
  Remote state Up, version 1
  Replicated

1 sessions, 1 clients
Cumulative transmit rate 10.0 pps, cumulative receive rate 10.0 pps

For more information about the configuration, use the show bfd session extensive command. The output for this command provides the keychain name, the authentication algorithm and mode for each client in the session, and the overall BFD authentication configuration status, keychain name, and authentication algorithm and mode.

user@host# show bfd session extensive    
                                                  Detect   Transmit
Address                  State     Interface      Time     Interval  Multiplier
10.9.1.33            Up        so-7/1/0.0          0.600     0.200      3
  Client OSPF, TX interval 0.200, RX interval 0.200, multiplier 3, Authenticate 
       keychain bfd-ospf, algo keyed-md5, mode loose

  Session up time 3d 00:34
  Local diagnostic None, remote diagnostic None
  Remote state Up, version 1
  Replicated
  Min async interval 0.200, min slow interval 1.000
  Adaptive async tx interval 0.200, rx interval 0.200
  Local min tx interval 0.200, min rx interval 0.200, multiplier 3
  Remote min tx interval 0.100, min rx interval 0.100, multiplier 3
  Threshold transmission interval 0.000, Threshold for detection time 0.000
  Local discriminator 11, remote discriminator 80
  Echo mode disabled/inactive
 Authentication enabled/active, keychain bfd-ospf, algo keyed-sha-1, mode strict  
1 sessions, 1 clients
Cumulative transmit rate 10.0 pps, cumulative receive rate 10.0 pps