Dynamic Site to Site IKEv2 VPN Tunnel Between Two ASAs Configuration Example

Introduction

This document describes how to configure a site-to-site Internet Key Exchange Version 2 (IKEv2) VPN tunnel between two Adaptive Security Appliances (ASAs) where one ASA has a dynamic IP address and the other has a static IP address.

Prerequisites

Requirements

There are no specific requirements for this document.

Components Used

The information in this document is based on these software and hardware versions:

• ASA Version 5505
• ASA Version 9.1(5)

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.

Background Information

There are two ways that this configuration can be set up:

• With the DefaultL2LGroup tunnel group
• With a named tunnel group

The biggest configuration difference between the two scenarios is the Internet Security Association and Key Management Protocol (ISAKMP) ID used by the remote ASA. When the DefaultL2LGroup is used on the static ASA, the peer's ISAKMP ID has to be the address. However if a named tunnel group is used, the peer's ISAKMP ID has to be the same the tunnel group name using this command:

crypto isakmp identity key-id <tunnel-group_name>

The advantage of using named tunnel groups on the static ASA is that when the DefaultL2LGroup is used, the configuration on the remote dynamic ASAs, which includes the pre-shared keys, has to be identical and it does not allow for much granularity with the setup of policies.

Network Diagram

Configure

This section describes the configuration on each ASA depending on which solution you decide to use. 

Solution 1 - Use of the DefaultL2LGroup

This is the simplest way to configure a LAN-to-LAN (L2L) tunnel betwen two ASAs when one ASA gets its address dynamically. The DefaultL2L Group is a preconfigured tunnel group on the ASA and all connections that do not explicitly match any particular tunnel group fall on this connection. Since the Dynamic ASA does not have a constant predetermined IP address, it means the admin cannot configure the Statis ASA in order to allow the connection on a specific tunnel group. In this situation, the DefaultL2L Group can be used in order to allow the dynamic connections.

Tip: With this method, the downside is that all peers will have the same pre-shared key since only one pre-shared key can be defined per tunnel-group and all of the peers will connect to the same DefaultL2LGroup tunnel-group.

Static ASA Configuration

interface Ethernet0/0
 nameif inside
 security-level 100
 IP address 172.30.2.6 255.255.255.0
!
interface Ethernet0/3
 nameif Outside
 security-level 0
 IP address 207.30.43.15 255.255.255.128
!
boot system disk0:/asa915-k8.bin
crypto ipsec IKEv2 ipsec-proposal Site2Site
 protocol esp encryption aes-256
 protocol esp integrity sha-1
crypto ipsec IKEv2 ipsec-proposal AES256
 protocol esp encryption aes-256
 protocol esp integrity sha-1 md5
crypto ipsec IKEv2 ipsec-proposal AES192
 protocol esp encryption aes-192
 protocol esp integrity sha-1 md5
crypto ipsec IKEv2 ipsec-proposal AES
 protocol esp encryption aes
 protocol esp integrity sha-1 md5
crypto ipsec IKEv2 ipsec-proposal 3DES
 protocol esp encryption 3des
 protocol esp integrity sha-1 md5
crypto ipsec IKEv2 ipsec-proposal DES
 protocol esp encryption des
 protocol esp integrity sha-1 md5
crypto engine large-mod-accel
crypto ipsec security-association pmtu-aging infinite
crypto dynamic-map SYSTEM_DEFAULT_CRYPTO_MAP 10 set IKEv2 ipsec-proposal AES256
AES192 AES 3DES DES
crypto dynamic-map SYSTEM_DEFAULT_CRYPTO_MAP 65535 set ikev1 transform-set
ESP-AES-128-SHA ESP-AES-128-MD5 ESP-AES-192-SHA ESP-AES-192-MD5 ESP-AES-
256-SHA ESP-AES-256-MD5 ESP-3DES-SHA ESP-3DES-MD5 ESP-DES-SHA ESP-DES-MD5
crypto dynamic-map SYSTEM_DEFAULT_CRYPTO_MAP 65535 set IKEv2 ipsec-proposal AES256
AES192 AES 3DES DES
crypto map Outside_map 65535 ipsec-isakmp dynamic SYSTEM_DEFAULT_CRYPTO_MAP
crypto map Outside_map interface Outside
crypto IKEv2 policy 2
 encryption aes-256
 integrity sha512
 group 24
 prf sha512
 lifetime seconds 86400
crypto IKEv2 policy 3
 encryption aes-256
 integrity sha group 5 2
 prf sha
 lifetime seconds 86400
crypto IKEv2 policy 10
 encryption aes-192
 integrity sha
 group 5 2
 prf sha
 lifetime seconds 86400
crypto IKEv2 policy 20
 encryption aes
 integrity sha
 group 5 2
 prf sha
 lifetime seconds 86400
crypto IKEv2 policy 30
 encryption 3des
 integrity sha
 group 5 2
 prf sha
 lifetime seconds 86400
crypto IKEv2 policy 40
 encryption des
 integrity sha
 group 5 2
 prf sha
 lifetime seconds 86400
crypto IKEv2 enable inside client-services port 443
crypto IKEv2 enable Outside client-services port 443
group-policy Site2Site internal
group-policy Site2Site attributes
 vpn-idle-timeout none
 vpn-session-timeout none
 vpn-filter none
 vpn-tunnel-protocol IKEv2 
tunnel-group DefaultL2LGroup general-attributes
 default-group-policy Site2Site
tunnel-group DefaultL2LGroup ipsec-attributes
 IKEv2 remote-authentication pre-shared-key *****
 IKEv2 local-authentication pre-shared-key *****

On the Adaptive Security Device Manager (ASDM), you can configure the DefaultL2LGroup as shown here:

Dynamic ASA

interface Ethernet0/0
 switchport access vlan 2
!
interface Ethernet0/1
!
interface Ethernet0/2
!
interface Ethernet0/3
!
interface Ethernet0/4
!
interface Ethernet0/5
!
interface Ethernet0/6
!
interface Ethernet0/7
!
interface Vlan1
 nameif inside
 security-level 100
 IP address 172.16.1.1 255.255.255.224
!
interface Vlan2
 nameif outside
 security-level 0
 IP address dhcp setroute
!
ftp mode passive
object network NETWORK_OBJ_172.16.1.0_24
 subnet 172.16.1.0 255.255.255.0
object-group network DM_INLINE_NETWORK_1
 network-object object 10.0.0.0
 network-object object 172.0.0.0
access-list outside_cryptomap extended permit IP 172.16.1.0 255.255.255.0
object-group DM_INLINE_NETWORK_1
nat (inside,outside) source static NETWORK_OBJ_172.16.1.0_24 NETWORK_OBJ_
172.16.1.0_24 destination static DM_INLINE_NETWORK_1 DM_INLINE_NETWORK_1
nat (inside,outside) source dynamic any interface
crypto ipsec IKEv2 ipsec-proposal Site2Site
 protocol esp encryption aes-256
 protocol esp integrity sha-1
crypto ipsec IKEv2 ipsec-proposal DES
 protocol esp encryption des
 protocol esp integrity sha-1 md5
crypto ipsec IKEv2 ipsec-proposal 3DES
 protocol esp encryption 3des
 protocol esp integrity sha-1 md5
crypto ipsec IKEv2 ipsec-proposal AES
 protocol esp encryption aes
 protocol esp integrity sha-1 md5
crypto ipsec IKEv2 ipsec-proposal AES192
 protocol esp encryption aes-192
 protocol esp integrity sha-1 md5
crypto ipsec IKEv2 ipsec-proposal AES256
 protocol esp encryption aes-256
 protocol esp integrity sha-1 md5
crypto ipsec security-association pmtu-aging infinite
crypto map outside_map 1 match address outside_cryptomap
crypto map outside_map 1 set pfs group5
crypto map outside_map 1 set peer 198.51.100.1
crypto map outside_map 1 set ikev1 phase1-mode aggressive group5
crypto map outside_map 1 set IKEv2 ipsec-proposal Site2Site
crypto map outside_map interface outside
crypto IKEv2 policy 2
 encryption aes-256
 integrity sha512
 group 24
 prf sha512
 lifetime seconds 86400
crypto IKEv2 policy 3
 encryption aes-256
 integrity sha
 group 5 2
 prf sha
 lifetime seconds 86400
crypto IKEv2 policy 10
 encryption aes-192
 integrity sha
 group 5 2
 prf sha
 lifetime seconds 86400
crypto IKEv2 policy 20
 encryption aes
 integrity sha
 group 5 2
 prf sha
 lifetime seconds 86400
crypto IKEv2 policy 30
 encryption 3des
 integrity sha
 group 5 2
 prf sha
 lifetime seconds 86400
crypto IKEv2 policy 40
 encryption des
 integrity sha
 group 5 2
 prf sha
 lifetime seconds 86400
crypto IKEv2 enable outside
management-access inside
group-policy GroupPolicy_198.51.100.1 internal
group-policy GroupPolicy_198.51.100.1 attributes
 vpn-tunnel-protocol IKEv2
tunnel-group 198.51.100.1 type ipsec-l2l
tunnel-group 198.51.100.1 general-attributes
 default-group-policy GroupPolicy_198.51.100.1
tunnel-group 198.51.100.1 ipsec-attributes
 ikev1 pre-shared-key *****
 IKEv2 remote-authentication pre-shared-key *****
 IKEv2 local-authentication pre-shared-key ***** 

On the ASDM, you can use the standard wizard in order to set up the appropriate connection profile or you can simply add a new connection and follow the standard procedure.

Solution 2 - Create a User-Defined Tunnel-Group

This method requires slighly more configuration, but it allows for more granularity. Each peer can have its own separate policy and pre-shared key. However here it is important to change the ISAKMP ID on the dynamic peer so that it uses a name instead of an IP address. This allows the static ASA to match the incoming ISAKMP initialisation request to the right tunnel group and to use the right policies.

Static ASA Configuration

interface Ethernet0/0
 nameif inside
 security-level 100
 IP address 172.16.0.1 255.255.255.0
!
interface Ethernet0/3
 nameif Outside
 security-level 0
 IP address 198.51.100.1 255.255.255.128
!
boot system disk0:/asa915-k8.bin
object-group network DM_INLINE_NETWORK_1
 network-object object 10.0.0.0
 network-object object 172.0.0.0

access-list Outside_cryptomap_1 extended permit IP object-group DM_INLINE_NETWORK_
1 172.16.1.0 255.255.255.0

crypto ipsec IKEv2 ipsec-proposal Site2Site
 protocol esp encryption aes-256
 protocol esp integrity sha-1
crypto ipsec IKEv2 ipsec-proposal AES256
 protocol esp encryption aes-256
 protocol esp integrity sha-1 md5
crypto ipsec IKEv2 ipsec-proposal AES192
 protocol esp encryption aes-192
 protocol esp integrity sha-1 md5
crypto ipsec IKEv2 ipsec-proposal AES
 protocol esp encryption aes
 protocol esp integrity sha-1 md5
crypto ipsec IKEv2 ipsec-proposal 3DES
 protocol esp encryption 3des
 protocol esp integrity sha-1 md5
crypto ipsec IKEv2 ipsec-proposal DES
 protocol esp encryption des
 protocol esp integrity sha-1 md5
crypto engine large-mod-accel
crypto ipsec security-association pmtu-aging infinite
crypto dynamic-map SYSTEM_DEFAULT_CRYPTO_MAP 65535 set ikev1 transform-set
ESP-AES-128-SHA ESP-AES-128-MD5 ESP-AES-192-SHA ESP-AES-192-MD5 ESP-AES-256-
SHA ESP-AES-256-MD5 ESP-3DES-SHA ESP-3DES-MD5 ESP-DES-SHA ESP-DES-MD5
crypto dynamic-map SYSTEM_DEFAULT_CRYPTO_MAP 65535 set IKEv2 ipsec-proposal
AES256 AES192 AES 3DES DES
crypto dynamic-map DynamicSite2Site1 4 match address Outside_cryptomap_1
crypto dynamic-map DynamicSite2Site1 4 set IKEv2 ipsec-proposal Site2Site
crypto map Outside_map 65534 ipsec-isakmp dynamic DynamicSite2Site1
crypto map Outside_map 65535 ipsec-isakmp dynamic SYSTEM_DEFAULT_CRYPTO_MAP
crypto map Outside_map interface Outside

crypto IKEv2 policy 2
 encryption aes-256
 integrity sha512
 group 24
 prf sha512
 lifetime seconds 86400
crypto IKEv2 policy 3
 encryption aes-256
 integrity sha
 group 5 2
 prf sha
 lifetime seconds 86400
crypto IKEv2 policy 10
 encryption aes-192
 integrity sha
 group 5 2
 prf sha
 lifetime seconds 86400
crypto IKEv2 policy 20
 encryption aes
 integrity sha
 group 5 2
 prf sha
 lifetime seconds 86400
crypto IKEv2 policy 30
 encryption 3des
 integrity sha
 group 5 2
 prf sha
 lifetime seconds 86400
crypto IKEv2 policy 40
 encryption des
 integrity sha
 group 5 2
 prf sha
 lifetime seconds 86400
crypto IKEv2 enable Outside client-services port 443
management-access inside 

group-policy GroupPolicy4 internal
group-policy GroupPolicy4 attributes
 vpn-tunnel-protocol IKEv2 

tunnel-group DynamicSite2Site1 type ipsec-l2l
tunnel-group DynamicSite2Site1 general-attributes
 default-group-policy GroupPolicy4
tunnel-group DynamicSite2Site1 ipsec-attributes
 IKEv2 remote-authentication pre-shared-key *****
 IKEv2 local-authentication pre-shared-key *****

On the ASDM, the connection profile name is an IP address by default. So when you create it, you must change it in order to give it a name as shown in the screenshot here:

Dynamic ASA Configuration

The Dynamic ASA is configured almost the same way in both solutions with the addition of one command as shown here: 

crypto isakmp identity key-id DynamicSite2Site1

As described previously, by default the ASA uses the IP address of the interface that the VPN tunnel is mapped to as the ISAKMP key-ID. However in this case, the key-ID on the dynamic ASA is the same as the name of the tunnel-group on the Static ASA. So on every dynamic peer, the key-id will be different and a corresponding tunnel-group must be created on the Static ASA with the right name.

On the ASDM, this can be configured as shown in this screenshot:

Verify

Use this section in order to confirm that your configuration works properly.

On the Static ASA 

Here is the result of the show crypto IKEv2 sa det command:

IKEv2 SAs:

Session-id:132, Status:UP-ACTIVE, IKE count:1, CHILD count:1

Tunnel-id                 Local                Remote     Status         Role
1574208993     198.51.100.1/4500    203.0.113.134/4500      READY    RESPONDER
      Encr: AES-CBC, keysize: 256, Hash: SHA512, DH Grp:24, Auth sign: PSK,
      Auth verify: PSK
      Life/Active Time: 86400/352 sec
      Session-id: 132
      Status Description: Negotiation done
      Local spi: 4FDFF215BDEC73EC       Remote spi: 2414BEA1E10E3F70
      Local id: 198.51.100.1
      Remote id: DynamicSite2Site1
      Local req mess id: 13             Remote req mess id: 17
      Local next mess id: 13            Remote next mess id: 17
      Local req queued: 13              Remote req queued: 17
      Local window: 1                   Remote window: 1
      DPD configured for 10 seconds, retry 2
      NAT-T is detected  outside
Child sa: local selector  172.0.0.0/0 - 172.255.255.255/65535
          remote selector 172.16.1.0/0 - 172.16.1.255/65535
          ESP spi in/out: 0x9fd5c736/0x6c5b3cc9 
          AH spi in/out: 0x0/0x0 
          CPI in/out: 0x0/0x0 
          Encr: AES-CBC, keysize: 256, esp_hmac: SHA96
          ah_hmac: None, comp: IPCOMP_NONE, mode tunnel

Here is the result of the show crypto ipsec sa command:

interface: Outside
    Crypto map tag: DynamicSite2Site1, seq num: 4, local addr: 198.51.100.1
 
      access-list Outside_cryptomap_1 extended permit IP 172.0.0.0 255.0.0.0
      172.16.1.0 255.255.255.0
      local ident (addr/mask/prot/port): (172.0.0.0/255.0.0.0/0/0)
      remote ident (addr/mask/prot/port): (172.16.1.0/255.255.255.0/0/0)
      current_peer: 203.0.113.134
  
      #pkts encaps: 1, #pkts encrypt: 1, #pkts digest: 1
      #pkts decaps: 12, #pkts decrypt: 12, #pkts verify: 12
      #pkts compressed: 0, #pkts decompressed: 0
      #pkts not compressed: 1, #pkts comp failed: 0, #pkts decomp failed: 0
      #pre-frag successes: 0, #pre-frag failures: 0, #fragments created: 0
      #PMTUs sent: 0, #PMTUs rcvd: 0, #decapsulated frgs needing reassembly: 0
      #TFC rcvd: 0, #TFC sent: 0
      #Valid ICMP Errors rcvd: 0, #Invalid ICMP Errors rcvd: 0
      #send errors: 0, #recv errors: 0
 
      local crypto endpt.: 198.51.100.1/4500, remote crypto endpt.: 
      203.0.113.134/4500
      path mtu 1500, ipsec overhead 82(52), media mtu 1500
      PMTU time remaining (sec): 0, DF policy: copy-df
      ICMP error validation: disabled, TFC packets: disabled
      current outbound spi: 6C5B3CC9
      current inbound spi : 9FD5C736
 
    inbound esp sas:
      spi: 0x9FD5C736 (2681587510)
         transform: esp-aes-256 esp-sha-hmac no compression
         in use settings ={L2L, Tunnel,  NAT-T-Encaps, IKEv2, }
         slot: 0, conn_id: 1081344, crypto-map: DynamicSite2Site1
         sa timing: remaining key lifetime (kB/sec): (4193279/28441)
         IV size: 16 bytes
         replay detection support: Y
         Anti replay bitmap:
          0x00000000 0x00001FFF
    outbound esp sas:
      spi: 0x6C5B3CC9 (1817918665)
         transform: esp-aes-256 esp-sha-hmac no compression
         in use settings ={L2L, Tunnel,  NAT-T-Encaps, IKEv2, }
         slot: 0, conn_id: 1081344, crypto-map: DynamicSite2Site1
         sa timing: remaining key lifetime (kB/sec): (3962879/28441)
         IV size: 16 bytes
         replay detection support: Y
         Anti replay bitmap:
          0x00000000 0x00000001

On the Dynamic ASA

Here is the result of the show crypto IKEv2 sa detail command:

IKEv2 SAs:

Session-id:11, Status:UP-ACTIVE, IKE count:1, CHILD count:1

Tunnel-id                 Local                Remote     Status         Role
1132933595   192.168.50.155/4500     198.51.100.1/4500      READY    INITIATOR
      Encr: AES-CBC, keysize: 256, Hash: SHA512, DH Grp:24, Auth sign: PSK,
      Auth verify: PSK
      Life/Active Time: 86400/267 sec
      Session-id: 11
      Status Description: Negotiation done
      Local spi: 2414BEA1E10E3F70       Remote spi: 4FDFF215BDEC73EC
      Local id: DynamicSite2Site1
      Remote id: 198.51.100.1
      Local req mess id: 13             Remote req mess id: 9
      Local next mess id: 13            Remote next mess id: 9
      Local req queued: 13              Remote req queued: 9
      Local window: 1                   Remote window: 1
      DPD configured for 10 seconds, retry 2
      NAT-T is detected inside
Child sa: local selector  172.16.1.0/0 - 172.16.1.255/65535
          remote selector 172.0.0.0/0 - 172.255.255.255/65535
          ESP spi in/out: 0x6c5b3cc9/0x9fd5c736 
          AH spi in/out: 0x0/0x0 
          CPI in/out: 0x0/0x0 
          Encr: AES-CBC, keysize: 256, esp_hmac: SHA96
          ah_hmac: None, comp: IPCOMP_NONE, mode tunnel

Here is the result of the show crypto ipsec sa command:

interface: outside
    Crypto map tag: outside_map, seq num: 1, local addr: 192.168.50.155

      access-list outside_cryptomap extended permit IP 172.16.1.0 255.255.255.0
      172.0.0.0 255.0.0.0
      local ident (addr/mask/prot/port): (172.16.1.0/255.255.255.0/0/0)
      remote ident (addr/mask/prot/port): (172.0.0.0/255.0.0.0/0/0)
      current_peer: 198.51.100.1

      #pkts encaps: 12, #pkts encrypt: 12, #pkts digest: 12
      #pkts decaps: 1, #pkts decrypt: 1, #pkts verify: 1
      #pkts compressed: 0, #pkts decompressed: 0
      #pkts not compressed: 12, #pkts comp failed: 0, #pkts decomp failed: 0
      #pre-frag successes: 0, #pre-frag failures: 0, #fragments created: 0
      #PMTUs sent: 0, #PMTUs rcvd: 0, #decapsulated frgs needing reassembly: 0
      #TFC rcvd: 0, #TFC sent: 0
      #Valid ICMP Errors rcvd: 0, #Invalid ICMP Errors rcvd: 0
      #send errors: 0, #recv errors: 0
 
      local crypto endpt.: 192.168.50.155/4500, remote crypto endpt.: 
      198.51.100.1/4500
      path mtu 1500, ipsec overhead 82(52), media mtu 1500
      PMTU time remaining (sec): 0, DF policy: copy-df
      ICMP error validation: disabled, TFC packets: disabled
      current outbound spi: 9FD5C736
      current inbound spi : 6C5B3CC9

    inbound esp sas:
      spi: 0x6C5B3CC9 (1817918665)
         transform: esp-aes-256 esp-sha-hmac no compression
         in use settings ={L2L, Tunnel,  NAT-T-Encaps, PFS Group 5, IKEv2, }
         slot: 0, conn_id: 77824, crypto-map: outside_map
         sa timing: remaining key lifetime (kB/sec): (4008959/28527)
         IV size: 16 bytes
         replay detection support: Y
         Anti replay bitmap:
          0x00000000 0x00000003
    outbound esp sas:
      spi: 0x9FD5C736 (2681587510)
         transform: esp-aes-256 esp-sha-hmac no compression
         in use settings ={L2L, Tunnel,  NAT-T-Encaps, PFS Group 5, IKEv2, }
         slot: 0, conn_id: 77824, crypto-map: outside_map
         sa timing: remaining key lifetime (kB/sec): (4147199/28527)
         IV size: 16 bytes
         replay detection support: Y
         Anti replay bitmap:
          0x00000000 0x00000001

The Output Interpreter Tool (registered customers only) supports certain show commands. Use the Output Interpreter Tool in order to view an analysis of show command output.

Troubleshoot

This section provides information you can use in order to troubleshoot your configuration.

The Output Interpreter Tool (registered customers only) supports certain show commands. Use the Output Interpreter Tool in order to view an analysis of show command output.

Note: Refer to Important Information on Debug Commands before you use debug commands.

• deb crypto IKEv2 packet
• deb crypto IKEv2 internal