IPsec Dead Peer Detection Periodic
Message Option

First Published: May 1, 2004
Last Updated: March 24, 2011

The IPsec Dead Peer Detection Periodic Message Option feature is used to configure the 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 feature information and caveats, see 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 for IPsec Dead Peer Detection Periodic Message Option" section.

Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Contents

•Prerequisites for IPsec Dead Peer Detection Periodic Message Option

•Restrictions for IPsec Dead Peer Detection Periodic Message Option

•Information About IPsec Dead Peer Detection Periodic Message Option

•How to Configure IPsec Dead Peer Detection Periodic Message Option

•Configuration Examples for IPsec Dead Peer Detection Periodic Message Option

•Additional References

•Feature Information for IPsec Dead Peer Detection Periodic Message Option

Prerequisites for IPsec Dead Peer Detection Periodic
Message 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 software in all modes of operation—site-to-site, Easy VPN remote, and Easy VPN server.

Restrictions for IPsec Dead Peer Detection Periodic
Message 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 Detection
Periodic Message Option

To configure IPsec Dead Peer Detection Periodic Message Option, you should understand the following concepts:

•How DPD and Cisco IOS Keepalive Features Work

•Using the IPsec Dead Peer Detection Periodic Message Option

•Using DPD and Cisco IOS Keepalive Features with Multiple Peers in the Crypto Map

•Using DPD in an Easy VPN Remote Configuration

How DPD and Cisco IOS Keepalive Features Work

DPD and Cisco IOS keepalives function on the basis of the timer. If the timer is set for 10 seconds, the router sends 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 does not discover this 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 initiates 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 Keepalive Features
with Multiple Peers in the Crypto Map

DPD and IOS 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 switches 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 Periodic
Message Option

This section contains the following tasks:

•Configuring a Periodic DPD Message

•Configuring DPD and Cisco IOS Keepalives with Multiple Peers in the Crypto Map

•Configuring DPD for an Easy VPN Remote

•Verifying That DPD Is Enabled

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 [retry-seconds] [periodic | on-demand]

DETAILED STEPS

 
Command or Action
Purpose

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 [retry-seconds] [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 Keepalives with Multiple Peers
in 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 causes 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 Action
Purpose

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 is 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 causes a router to cycle through the peer list when it detects that the first peer is dead.

Note IOS 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

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

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 Detection
Periodic Message Option

This section provides the following configuration examples:

•Site-to-Site Setup with Periodic DPD Enabled: Example

•Easy VPN Remote with DPD Enabled: Example

•Verifying DPD Configuration Using the debug crypto isakmp Command: Example

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

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

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 3des

  authentication pre-share

  group 2

!

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 esp-3des-sha esp-3des esp-sha-hmac

crypto map test 1 ipsec-isakmp

  set peer 10.2.80.209

  set transform-set esp-3des-sha

  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 resends 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 Ethernet0

  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 Keepalives Used in Conjunction with Multiple Peers in a Crypto Map: Example

The following example shows that DPD and Cisco IOS keepalives are used in conjunction with multiple peers in a crypto map configuration when IKE is 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

Related Documents

Related Topic
Document Title

Configuring IPsec

Configuring Security for VPNs with IPsec

IPsec commands

Cisco IOS Security Command Reference


Standards

Standards
Title

None

—


MIBs

MIBs
MIBs Link

None

To locate and download MIBs for selected platforms, Cisco IOS software 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 and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

http://www.cisco.com/cisco/web/support/index.html


Feature Information for IPsec Dead Peer Detection Periodic Message Option

Table 1 lists the release history for this feature.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Note Table 1 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.

Table 1 Feature Information for IPsec Dead Peer Detection Periodic Message Option 

Feature Name
Releases
Feature Information

IPsec Dead Peer Detection Periodic Message Option

12.3(7)T
12.2(33)SRA
12.2(33)SXH

The IPsec Dead Peer Detection Periodic Message Option feature is used to configure the 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.

This feature was introduced in Cisco IOS Release 12.3(7)T.

This feature was integrated into Cisco IOS Release 12.2(33)SRA

This feature was integrated into Cisco IOS Release 12.2(33)SXH

The following command was introduced: crypto isakmp keepalive.


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