IPsec Dead Peer Detection PeriodicMessage Option

The IPsec Dead Peer Detection Periodic Message Option feature allows you to configure your router to query the liveliness of its Internet Key Exchange (IKE) peer at regular intervals. The benefit of this approach over the default approach (on-demand dead peer detection) is earlier detection of dead peers.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table.

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Prerequisites for IPsec Dead Peer Detection PeriodicMessage Option

Before configuring the IPsec Dead Peer Detection Periodic Message Option feature, you should have the following:

  • Familiarity with configuring IP Security (IPsec).

  • An IKE peer that supports DPD (dead peer detection). Implementations that support DPD include the Cisco VPN 3000 concentrator, Cisco PIX Firewall, Cisco VPN Client, and Cisco IOS XE software in all modes of operation--site-to-site, Easy VPN remote, and Easy VPN server.

Restrictions for IPsec Dead Peer Detection PeriodicMessage Option

Using periodic DPD potentially allows the router to detect an unresponsive IKE peer with better response time when compared to on-demand DPD. However, use of periodic DPD incurs extra overhead. When communicating to large numbers of IKE peers, you should consider using on-demand DPD instead.

Information About IPsec Dead Peer DetectionPeriodic Message Option

How DPD and Cisco IOS XE Keepalive Features Work

DPD and Cisco IOS XE keepalives function on the basis of the timer. If the timer is set for 10 seconds, the router will send a “hello” message every 10 seconds (unless, of course, the router receives a “hello” message from the peer). The benefit of IOS keepalives and periodic DPD is earlier detection of dead peers. However, IOS keepalives and periodic DPD rely on periodic messages that have to be sent with considerable frequency. The result of sending frequent messages is that the communicating peers must encrypt and decrypt more packets.

DPD also has an on-demand approach. The contrasting on-demand approach is the default. With on-demand DPD, messages are sent on the basis of traffic patterns. For example, if a router has to send outbound traffic and the liveliness of the peer is questionable, the router sends a DPD message to query the status of the peer. If a router has no traffic to send, it never sends a DPD message. If a peer is dead, and the router never has any traffic to send to the peer, the router will not find out until the IKE or IPsec security association (SA) has to be rekeyed (the liveliness of the peer is unimportant if the router is not trying to communicate with the peer). On the other hand, if the router has traffic to send to the peer, and the peer does not respond, the router will initiate a DPD message to determine the state of the peer.

Using the IPsec Dead Peer Detection Periodic Message Option

With the IPsec Dead Peer Detection Periodic Message Option feature, you can configure your router so that DPD messages are “forced” at regular intervals. This forced approach results in earlier detection of dead peers. For example, if a router has no traffic to send, a DPD message is still sent at regular intervals, and if a peer is dead, the router does not have to wait until the IKE SA times out to find out.

If you want to configure the DPD periodic message option, you should use the crypto isakmp keepalive command with the periodic keyword. If you do not configure the periodic keyword, the router defaults to the on-demand approach.


Note

When the crypto isakmp keepalive command is configured, the Cisco IOS software negotiates the use of Cisco IOS keepalives or DPD, depending on which protocol the peer supports.

Using DPD and Cisco IOS XE Keepalive Featureswith Multiple Peers in the Crypto Map

DPD and Cisco IOS XE keepalive features can be used in conjunction with multiple peers in the crypto map to allow for stateless failover. DPD allows the router to detect a dead IKE peer, and when the router detects the dead state, the router deletes the IPsec and IKE SAs to the peer. If you configure multiple peers, the router will switch over to the next listed peer for a stateless failover.

Using DPD in an Easy VPN Remote Configuration

DPD can be used in an Easy VPN remote configuration. See the section Configuring DPD for an Easy VPN Remote section.

How to Configure IPsec Dead Peer Detection PeriodicMessage Option

Configuring a Periodic DPD Message

To configure a periodic DPD message, perform the following steps.

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    crypto isakmp keepalive seconds [retries] [periodic | on-demand]


DETAILED STEPS
     Command or ActionPurpose
    Step 1 enable


    Example:
    Router> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.

     
    Step 2 configure terminal


    Example:
    Router# configure terminal
     

    Enters global configuration mode.

     
    Step 3 crypto isakmp keepalive seconds [retries] [periodic | on-demand]


    Example:
    Router (config)# crypto isakmp keepalive 10 periodic
     

    Allows the gateway to send DPD messages to the peer.

    • seconds --When the periodic keyword is used, this argument is the number of seconds between DPD messages; the range is from 10 to 3600 seconds.

    When the on-demand keyword is used, this argument is the number of seconds during which traffic is not received from the peer before DPD retry messages are sent if there is data (IPSec) traffic to send; the range is from 10 to 3600 seconds.

    Note   

    If you do not specify a time interval, an error message appears.

    • retry-seconds --(Optional) Number of seconds between DPD retry messages if the DPD retry message is missed by the peer; the range is from 2 to 60 seconds.

    Once 1 DPD message is missed by the peer, the router moves to a more aggressive state and sends the DPD retry message at the faster retry interval, which is the number of seconds between DPD retries if the DPD message is missed by the peer. The default DPD retry message is sent every 2 seconds. Five aggressive DPD retry messages can be missed before the tunnel is marked as down.

    Note   

    To configure DPD with IPsec High Availability (HA), the recommendation is to use a value other than the default (which is 2 seconds). A keepalive timer of 10 seconds with 5 retries seems to work well with HA because of the time that it takes for the router to get into active mode.

    • periodic --(Optional) DPD messages are sent at regular intervals.

    • on-demand --(Optional) The default behavior. DPD retries are sent on demand.

    Note   

    Because this option is the default, the on-demand keyword does not appear in configuration output.

     

    Configuring DPD and Cisco IOS XE Keepalives with Multiple Peersin the Crypto Map

    To configure DPD and IOS keepalives to be used in conjunction with the crypto map to allow for stateless failover, perform the following steps. This configuration will cause a router to cycle through the peer list when it detects that the first peer is dead.

    SUMMARY STEPS

      1.    enable

      2.    configure terminal

      3.    crypto map map-name seq-num ipsec-isakmp

      4.    set peer {host-name [dynamic] | ip-address}

      5.    set transform-set transform-set-name

      6.    match address [access-list-id | name]


    DETAILED STEPS
       Command or ActionPurpose
      Step 1 enable


      Example:
      Router> enable
       

      Enables privileged EXEC mode.

      • Enter your password if prompted.

       
      Step 2 configure terminal


      Example:
      Router# configure terminal
       

      Enters global configuration mode.

       
      Step 3 crypto map map-name seq-num ipsec-isakmp


      Example:
      Router (config)# crypto map green 1 ipsec-isakmp
       

      Enters crypto map configuration mode and creates or modifies a crypto map entry.

      • The ipsec-isakmp keyword indicates that IKE will be used to establish the IPsec SAs for protecting the traffic specified by this crypto map entry.

       
      Step 4 set peer {host-name [dynamic] | ip-address}


      Example:
      Router (config-crypto-map)# set peer 10.12.12.12
       

      Specifies an IPsec peer in a crypto map entry.

      • You can specify multiple peers by repeating this command.

       
      Step 5 set transform-set transform-set-name


      Example:
      Router (config-crypto-map)# set transform-set txfm
       

      Specifies which transform sets can be used with the crypto map entry.

      • You can specify more than one transform set name by repeating this command.

       
      Step 6 match address [access-list-id | name]


      Example:
      Router (config-crypto-map)# match address 101
       

      Specifies an extended access list for a crypto map entry.

       

      Configuring DPD for an Easy VPN Remote

      To configure DPD in an Easy VPN remote configuration, perform the following steps. This configuration also will cause a router to cycle through the peer list when it detects that the first peer is dead.


      Note

      Cisco IOS XE keepalives are not supported for Easy VPN remote configurations.

      SUMMARY STEPS

        1.    enable

        2.    configure terminal

        3.    crypto ipsec client ezvpn name

        4.    connect {auto | manual}

        5.    group group-name key group-key

        6.    mode {client | network-extension}

        7.    peer {ipaddress | hostname}


      DETAILED STEPS
         Command or ActionPurpose
        Step 1 enable


        Example:
        Router> enable
         

        Enables privileged EXEC mode.

        • Enter your password if prompted.

         
        Step 2 configure terminal


        Example:
        Router# configure terminal
         

        Enters global configuration mode.

         
        Step 3 crypto ipsec client ezvpn name


        Example:
        Router (config)# crypto ipsec client ezvpn ezvpn-config1
         

        Creates a Cisco Easy VPN remote configuration and enters the Cisco Easy VPN Remote configuration mode.

         
        Step 4 connect {auto | manual}


        Example:
        Router (config-crypto-ezvpn)# connect manual
         

        Manually establishes and terminates an IPsec VPN tunnel on demand.

        • The auto keyword option is the default setting.

         
        Step 5 group group-name key group-key


        Example:
        Router (config-crypto-ezvpn)# group unity key preshared
         

        Specifies the group name and key value for the Virtual Private Network (VPN) connection.

         
        Step 6 mode {client | network-extension}


        Example:
        Router (config-crypto-ezvpn)# mode client
         

        Specifies the VPN mode of operation of the router.

         
        Step 7 peer {ipaddress | hostname}


        Example:
        Router (config-crypto-ezvpn)# peer 10.10.10.10
         

        Sets the peer IP address or host name for the VPN connection.

        • A hostname can be specified only when the router has a DNS server available for host-name resolution.

        • This command can be repeated multiple times.

         

        Verifying That DPD Is Enabled

        DPD allows the router to clear the IKE state when a peer becomes unreachable. If DPD is enabled and the peer is unreachable for some time, you can use the clear crypto session command to manually clear IKE and IPsec SAs.

        The debug crypto isakmp command can be used to verify that DPD is enabled.

        SUMMARY STEPS

          1.    enable

          2.    clear crypto session [local ip-address [port local-port]] [remote ip-address [port remote-port]] | [fvrf vrf-name] [ivrf vrf-name]

          3.    debug crypto isakmp


        DETAILED STEPS
           Command or ActionPurpose
          Step 1 enable


          Example:
          Router> enable
           

          Enables privileged EXEC mode.

          • Enter your password if prompted.

           
          Step 2 clear crypto session [local ip-address [port local-port]] [remote ip-address [port remote-port]] | [fvrf vrf-name] [ivrf vrf-name]


          Example:
          Router# clear crypto session
           

          Deletes crypto sessions (IPsec and IKE SAs).

           
          Step 3 debug crypto isakmp


          Example:
          Router# debug crypto isakmp
           

          Displays messages about IKE events.

           

          Configuration Examples for IPsec Dead Peer DetectionPeriodic Message Option

          Site-to-Site Setup with Periodic DPD Enabled Example

          The following configurations are for a site-to-site setup with no periodic DPD enabled. The configurations are for the IKE Phase 1 policy and for the IKE preshared key.

          IKE Phase 1 Policy

          crypto isakmp policy 1
  encryption aes
  authentication pre-share
  group 14
!

          IKE Preshared Key

          crypto isakmp key kd94j1ksldz address 10.2.80.209 255.255.255.0
crypto isakmp keepalive 10 periodic
crypto ipsec transform-set Trans1 esp-aes esp-sha-hmac
crypto map test 1 ipsec-isakmp
  set peer 10.2.80.209
  set transform-set Trans1
  match address 101
!
!
interface FastEthernet0
  ip address 10.1.32.14 255.255.255.0
  speed auto
  crypto map test
!

          Easy VPN Remote with DPD Enabled Example

          The following configuration tells the router to send a periodic DPD message every 30 seconds. If the peer fails to respond to the DPD R_U_THERE message, the router will resend the message every 20 seconds (four transmissions altogether).

          crypto isakmp keepalive 30 20 periodic
crypto ipsec client ezvpn ezvpn-config
  connect auto
  group unity key preshared
  mode client
  peer 10.2.80.209
!
!
interface FastEthernet0
  ip address 10.2.3.4 255.255.255.0
  half-duplex
  crypto ipsec client ezvpn ezvpn-config inside
!
interface FastEthernet0
  ip address 10.1.32.14 255.255.255.0
  speed auto
  crypto ipsec client ezvpn ezvpn-config outside

          Verifying DPD Configuration Using the debug crypto isakmp Command Example

          The following sample output from the debug crypto isakmp command verifies that IKE DPD is enabled:

          *Mar 25 15:17:14.131: ISAKMP:(0:1:HW:2):IKE_DPD is enabled, initializing timers

          To see that IKE DPD is enabled (and that the peer supports DPD): when periodic DPD is enabled, you should see the following debug messages at the interval specified by the command:

          *Mar 25 15:18:52.107: ISAKMP:(0:1:HW:2): sending packet to 10.2.80.209 my_port 
500 peer_port 500 (I) QM_IDLE
*Mar 25 15:18:52.107: ISAKMP:(0:1:HW:2):purging node 899852982 *Mar 25 15:18:52.111: ISAKMP:(0:1:HW:2):Input = IKE_MESG_FROM_TIMER, 
IKE_TIMER_IM_ALIVE
*Mar 25 15:18:52.111: ISAKMP:(0:1:HW:2):Old State = IKE_P1_COMPLETE  New State = 
IKE_P1_COMPLETE

          The above message corresponds to sending the DPD R_U_THERE message.

          *Mar 25 15:18:52.123: ISAKMP (0:268435457): received packet from 10.2.80.209 
dport 500 sport 500 Global (I) QM_IDLE
*Mar 25 15:18:52.123: ISAKMP: set new node -443923643 to QM_IDLE *Mar 25 15:18:52.131: ISAKMP:(0:1:HW:2): processing HASH payload. message ID = 
-443923643
*Mar 25 15:18:52.131: ISAKMP:(0:1:HW:2): processing NOTIFY R_U_THERE_ACK protocol 1
	spi 0, message ID = -443923643, sa = 81BA4DD4
*Mar 25 15:18:52.135: ISAKMP:(0:1:HW:2): DPD/R_U_THERE_ACK received from peer 
10.2.80.209, sequence 0x9
*Mar 25 15:18:52.135: ISAKMP:(0:1:HW:2):deleting node -443923643 error FALSE 
reason "informational (in) state 1"
*Mar 25 15:18:52.135: ISAKMP:(0:1:HW:2):Input = IKE_MESG_FROM_PEER, IKE_INFO_NOTIFY *Mar 25 15:18:52.135: ISAKMP:(0:1:HW:2):Old State = IKE_P1_COMPLETE  New State = 
IKE_P1_COMPLETE

          The above message corresponds to receiving the acknowledge (ACK) message from the peer.

          Router#
*Mar 25 15:47:35.335: ISAKMP: set new node -90798077 to QM_IDLE *Mar 25 15:47:35.343: ISAKMP:(0:1:HW:2): sending packet to 10.2.80.209 my_port 
500 peer_port 500 (I) QM_IDLE
*Mar 25 15:47:35.343: ISAKMP:(0:1:HW:2):purging node -90798077 *Mar 25 15:47:35.347: ISAKMP:(0:1:HW:2):Input = IKE_MESG_FROM_TIMER, 
IKE_TIMER_IM_ALIVE
*Mar 25 15:47:35.347: ISAKMP:(0:1:HW:2):Old State = IKE_P1_COMPLETE  New State = 
IKE_P1_COMPLETE
*Mar 25 15:47:36.611: ISAKMP:(0:1:HW:2):purging node 1515050537 *Mar 25 15:47:37.343: ISAKMP:(0:1:HW:2):incrementing error counter on sa: 
PEERS_ALIVE_TIMER
*Mar 25 15:47:37.343: ISAKMP: set new node -1592471565 to QM_IDLE *Mar 25 15:47:37.351: ISAKMP:(0:1:HW:2): sending packet to 10.2.80.209 my_port 
500 peer_port 500 (I) QM_IDLE
*Mar 25 15:47:37.351: ISAKMP:(0:1:HW:2):purging node -1592471565 *Mar 25 15:47:37.355: ISAKMP:(0:1:HW:2):Input = IKE_MESG_FROM_TIMER, 
IKE_TIMER_PEERS_ALIVE
*Mar 25 15:47:37.355: ISAKMP:(0:1:HW:2):Old State = IKE_P1_COMPLETE  New State = 
IKE_P1_COMPLETE
*Mar 25 15:47:39.355: ISAKMP:(0:1:HW:2):incrementing error counter on sa: 
PEERS_ALIVE_TIMER
*Mar 25 15:47:39.355: ISAKMP: set new node 1758739401 to QM_IDLE *Mar 25 15:47:39.363: ISAKMP:(0:1:HW:2): sending packet to 10.2.80.209 my_port 
500 peer_port 500 (I) QM_IDLE
*Mar 25 15:47:39.363: ISAKMP:(0:1:HW:2):purging node 1758739401 *Mar 25 15:47:39.367: ISAKMP:(0:1:HW:2):Input = IKE_MESG_FROM_TIMER, 
IKE_TIMER_PEERS_ALIVE
*Mar 25 15:47:39.367: ISAKMP:(0:1:HW:2):Old State = IKE_P1_COMPLETE  New State = 
IKE_P1_COMPLETE
*Mar 25 15:47:41.367: ISAKMP:(0:1:HW:2):incrementing error counter on sa: 
PEERS_ALIVE_TIMER
*Mar 25 15:47:41.367: ISAKMP: set new node 320258858 to QM_IDLE *Mar 25 15:47:41.375: ISAKMP:(0:1:HW:2): sending packet to 10.2.80.209 my_port 
500 peer_port 500 (I) QM_IDLE
*Mar 25 15:47:41.379: ISAKMP:(0:1:HW:2):purging node 320258858 *Mar 25 15:47:41.379: ISAKMP:(0:1:HW:2):Input = IKE_MESG_FROM_TIMER, 
IKE_TIMER_PEERS_ALIVE
*Mar 25 15:47:41.379: ISAKMP:(0:1:HW:2):Old State = IKE_P1_COMPLETE  New State = 
IKE_P1_COMPLETE
*Mar 25 15:47:43.379: ISAKMP:(0:1:HW:2):incrementing error counter on sa: 
PEERS_ALIVE_TIMER
*Mar 25 15:47:43.379: ISAKMP: set new node -744493014 to QM_IDLE *Mar 25 15:47:43.387: ISAKMP:(0:1:HW:2): sending packet to 10.2.80.209 my_port 
500 peer_port 500 (I) QM_IDLE
*Mar 25 15:47:43.387: ISAKMP:(0:1:HW:2):purging node -744493014 *Mar 25 15:47:43.391: ISAKMP:(0:1:HW:2):Input = IKE_MESG_FROM_TIMER, 
IKE_TIMER_PEERS_ALIVE
*Mar 25 15:47:43.391: ISAKMP:(0:1:HW:2):Old State = IKE_P1_COMPLETE  New State = 
IKE_P1_COMPLETE
*Mar 25 15:47:45.391: ISAKMP:(0:1:HW:2):incrementing error counter on sa: 
PEERS_ALIVE_TIMER
*Mar 25 15:47:45.391: ISAKMP:(0:1:HW:2):peer 10.2.80.209 not responding! *Mar 25 15:47:45.391: ISAKMP:(0:1:HW:2):peer does not do paranoid keepalives.
*Mar 25 15:47:45.391: ISAKMP:(0:1:HW:2):deleting SA reason "peers alive" state 
(I) QM_IDLE       (peer 10.2.80.209) input queue 0
*Mar 25 15:47:45.395: ISAKMP: Unlocking IPSEC struct 0x81E5C4E8 from 
delete_siblings, count 0
*Mar 25 15:47:45.395: %CRYPTO-5-SESSION_STATUS: Crypto tunnel is DOWN.  Peer 
10.2.80.209:500       Id: 10.2.80.209
*Mar 25 15:47:45.399: ISAKMP: set new node -2061951065 to QM_IDLE *Mar 25 15:47:45.411: ISAKMP:(0:1:HW:2): sending packet to 10.2.80.209 my_port 
500 peer_port 500 (I) QM_IDLE
*Mar 25 15:47:45.411: ISAKMP:(0:1:HW:2):purging node -2061951065 *Mar 25 15:47:45.411: ISAKMP:(0:1:HW:2):Input = IKE_MESG_FROM_TIMER, 
IKE_TIMER_PEERS_ALIVE
*Mar 25 15:47:45.411: ISAKMP:(0:1:HW:2):Old State = IKE_P1_COMPLETE  New State = 
IKE_DEST_SA
*Mar 25 15:47:45.415: ISAKMP:(0:1:HW:2):deleting SA reason "peers alive" state 
(I) QM_IDLE       (peer 10.2.80.209) input queue 0
*Mar 25 15:47:45.415: ISAKMP: Unlocking IKE struct 0x81E5C4E8 for 
isadb_mark_sa_deleted(), count 0
*Mar 25 15:47:45.415: ISAKMP: Deleting peer node by peer_reap for 10.2.80.209: 
81E5C4E8
*Mar 25 15:47:45.415: ISAKMP:(0:1:HW:2):deleting node -1067612752 error TRUE 
reason "peers alive"
*Mar 25 15:47:45.415: ISAKMP:(0:1:HW:2):deleting node -114443536 error TRUE 
reason "peers alive"
*Mar 25 15:47:45.419: ISAKMP:(0:1:HW:2):deleting node 2116015069 error TRUE 
reason "peers alive"
*Mar 25 15:47:45.419: ISAKMP:(0:1:HW:2):deleting node -1981865558 error TRUE 
reason "peers alive"
*Mar 25 15:47:45.419: ISAKMP:(0:1:HW:2):Input = IKE_MESG_INTERNAL, IKE_PHASE1_DEL *Mar 25 15:47:45.419: ISAKMP:(0:1:HW:2):Old State = IKE_DEST_SA  New State = 
IKE_DEST_SA
*Mar 25 15:47:45.419: ISAKMP: received ke message (4/1)
*Mar 25 15:47:45.419: ISAKMP: received ke message (3/1)
*Mar 25 15:47:45.423: ISAKMP: ignoring request to send delete notify (no ISAKMP 
sa) src 10.1.32.14 dst 10.2.80.209 for SPI 0x3A7B69BF
*Mar 25 15:47:45.423: ISAKMP:(0:1:HW:2):deleting SA reason "" state (I) 
MM_NO_STATE (peer 10.2.80.209) input queue 0
*Mar 25 15:47:45.423: ISAKMP:(0:1:HW:2):deleting node -1067612752 error FALSE 
reason ""
*Mar 25 15:47:45.423: ISAKMP:(0:1:HW:2):deleting node -114443536 error FALSE 
reason ""
*Mar 25 15:47:45.423: ISAKMP:(0:1:HW:2):deleting node 2116015069 error FALSE 
reason ""
*Mar 25 15:47:45.427: ISAKMP:(0:1:HW:2):deleting node -1981865558 error FALSE 
reason ""
*Mar 25 15:47:45.427: ISAKMP:(0:1:HW:2):Input = IKE_MESG_FROM_PEER, IKE_MM_EXCH *Mar 25 15:47:45.427: ISAKMP:(0:1:HW:2):Old State = IKE_DEST_SA  New State = 
IKE_DEST_SA

          The above message shows what happens when the remote peer is unreachable. The router sends one DPD R_U_THERE message and four retransmissions before it finally deletes the IPsec and IKE SAs.

          DPD and Cisco IOS XE Keepalives Used in Conjunction with Multiple Peers in a Crypto Map Example

          The following example shows that DPD and Cisco IOS XE keepalives are used in conjunction with multiple peers in a crypto map configuration when IKE will be used to establish the security associations (SAs). In this example, an SA could be set up to the IPsec peer at 10.0.0.1, 10.0.0.2, or 10.0.0.3.

          crypto map green 1 ipsec-isakmp
  set peer 10.0.0.1
  set peer 10.0.0.2
  set peer 10.0.0.3
  set transform-set txfm
  match address 101

          DPD Used in Conjunction with Multiple Peers for an Easy VPN Remote Example

          The following example shows that DPD is used in conjunction with multiple peers in an Easy VPN remote configuration. In this example, an SA could be set up to the IPsec peer at 10.10.10.10, 10.2.2.2, or 10.3.3.3.

          crypto ipsec client ezvpn ezvpn-config
  connect auto
  group unity key preshared
  mode client
  peer 10.10.10.10
  peer 10.2.2.2
  peer 10.3.3.3

          Additional References

          The following sections provide references related to IPsec Dead Peer Detection Periodic Message Option.

          Related Documents

          Related Topic

          Document Title

          Configuring IPsec

          Configuring Security for VPNs with IPsec

          IPsec commands

          Cisco IOS Security Command Reference

          Standards

          Standards

          Title

          No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

          --

          MIBs

          MIBs

          MIBs Link

          No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.

          To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

          http:/​/​www.cisco.com/​go/​mibs

          RFCs

          RFCs

          Title

          DPD conforms to the Internet draft “draft-ietf-ipsec-dpd-04.txt,” which is pending publication as an Informational RFC (a number has not yet been assigned).

          --

          Technical Assistance

          Description

          Link

          The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies.

          To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds.

          Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.

          http:/​/​www.cisco.com/​techsupport

          Feature Information for Dead Peer DetectionPeriodic Message Option

          The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

          Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.
          Table 1 Feature Information for Dead Peer Detection

          Feature Name

          Releases

          Feature Information

          Dead Peer Detection Periodic Message Option

          Cisco IOS XE Release 2.1

          This feature allows you to configure your router to query the liveliness of its IKE peer at regular intervals. The benefit of this approach over the default approach (on-demand dead peer detection) is earlier detection of dead peers.

          The following command was introduced or modified: crypto isakmp keepalive.