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FlexVPN Site-to-Site without Smart Defaults

In our FlexVPN site-to-site smart defaults lesson, we configure a site-to-site VPN using smart defaults. In this lesson, we’ll configure the same thing but we are not going to use smart defaults. This means we have to configure all of this:

  • IKEv2
    • IKEv2 Proposal
    • IKEv2 Policy
    • IKEv2 Keyring
    • IKEv2 Profile
  • IPSec
    • IPSec Transform-set
    • IPSec Profile

I’ll walk you through the entire configuration and we’ll take a look at some show commands to verify our work.

Configuration

This is the topology we are going to use:

Flexvpn Site To Site Smart Defaults Lab Topology

We have two routers with a static tunnel interface. I’m using IOSv Version 15.9(3)M2.

Configurations

Want to take a look for yourself? Here you will find the startup configuration of each device.

R1

hostname R1
!
ip cef
!
interface GigabitEthernet0/0
 ip address 192.168.12.1 255.255.255.0
!
end

R2

hostname R2
!
ip cef
!
interface GigabitEthernet0/0
 ip address 192.168.12.2 255.255.255.0
!
end

R1

Let’s start with R1.

IKEv2

There are four IKEv2 components we need to configure:

  • IKEv2 Proposal
  • IKEv2 Policy
  • IKEv2 Keyring
  • IKEv2 Profile
IKEv2 Proposal

The proposal is a collection of items we use in the negotiation of the IKEv2 security association (SA). Let’s configure one:

R1(config)#crypto ikev2 proposal IKEV2_PROPOSAL
R1(config-ikev2-proposal)#encryption aes-cbc-256
R1(config-ikev2-proposal)#group 15
R1(config-ikev2-proposal)#integrity sha256
IKEv2 Policy

We also need an IKEv2 policy. This policy contains proposals we want to use in the negotiation. We create a new policy and refer to the proposal we just created:

R1(config)#crypto ikev2 policy IKEV2_POLICY
R1(config-ikev2-policy)#proposal IKEV2_PROPOSAL
IKEv2 Keyring

We need a keyring that contains the pre-shared key(s) we want to use.

R1(config)#crypto ikev2 keyring IKEV2_KEYRING
R1(config-ikev2-keyring)#peer R2
R1(config-ikev2-keyring-peer)#address 192.168.12.2
R1(config-ikev2-keyring-peer)#pre-shared-key local CISCO
R1(config-ikev2-keyring-peer)#pre-shared-key remote CISCO
IKEv2 Profile

In the IKEv2 profile, we configure the local and remote identity and the authentication we want to use. This is where we refer to the keyring we created:

R1(config)#crypto ikev2 profile IKEV2_PROFILE
R1(config-ikev2-profile)#match identity remote fqdn R2.NWL.LAB
R1(config-ikev2-profile)#identity local fqdn R1.NWL.LAB
R1(config-ikev2-profile)#authentication local pre-share 
R1(config-ikev2-profile)#authentication remote pre-share 
R1(config-ikev2-profile)#keyring local IKEV2_KEYRING

This completes our IKEv2 configuration on R1.

IPSec

Next up is IPSec.

IPSec Transform-Set

The transform-set is where we configure the encryption and hashing algorithms we want to use:

R1(config)#crypto ipsec transform-set IPSEC_TRANSFORM_SET esp-aes 256 esp-sha256-hmac
The default IPSec mode is tunnel mode. If you want to use transport mode, you can configure it under the transform-set.
IPSec Profile

The second part of the IPSec configuration is the profile. This is where we combine the IKEv2 profile and our IPSec transform-set:

R1(config)#crypto ipsec profile IPSEC_PROFILE
R1(ipsec-profile)#set ikev2-profile IKEV2_PROFILE
R1(ipsec-profile)#set transform-set IPSEC_TRANSFORM_SET

This completes the IPSec configuration.

Tunnel Interface

The last part of our site-to-site configuration is the tunnel interface. This is where we attach the IPSec profile:

R1(config)#interface tunnel 0
R1(config-if)#ip address 172.16.12.1 255.255.255.0
R1(config-if)#tunnel source gigabitEthernet 0/0
R1(config-if)#tunnel destination 192.168.12.2
R1(config-if)#tunnel protection ipsec profile IPSEC_PROFILE

And that wraps up our VPN configuration on R1.

R2

We’ll do the exact same thing on R2. Here are all the commands:

R2(config)#crypto ikev2 proposal IKEV2_PROPOSAL 
R2(config-ikev2-proposal)#encryption aes-cbc-256
R2(config-ikev2-proposal)#integrity sha256
R2(config-ikev2-proposal)#group 15

R2(config)#crypto ikev2 policy IKEV2_POLICY 
R2(config-ikev2-policy)#proposal IKEV2_PROPOSAL

R2(config)#crypto ikev2 keyring IKEV2_KEYRING
R2(config-ikev2-keyring)#peer R1
R2(config-ikev2-keyring-peer)#address 192.168.12.1
R2(config-ikev2-keyring-peer)#pre-shared-key local CISCO
R2(config-ikev2-keyring-peer)#pre-shared-key remote CISCO

R2(config)#crypto ikev2 profile IKEV2_PROFILE
R2(config-ikev2-profile)#match identity remote fqdn R1.NWL.LAB
R2(config-ikev2-profile)#identity local fqdn R2.NWL.LAB
R2(config-ikev2-profile)#authentication remote pre-share
R2(config-ikev2-profile)#authentication local pre-share
R2(config-ikev2-profile)#keyring local IKEV2_KEYRING

R2(config)#crypto ipsec transform-set IPSEC_TRANSFORM_SET esp-aes 256 esp-sha256-hmac     

R2(config)#crypto ipsec profile IPSEC_PROFILE
R2(ipsec-profile)#set transform-set IPSEC_TRANSFORM_SET 
R2(ipsec-profile)#set ikev2-profile IKEV2_PROFILE

R2(config)#interface Tunnel0
R2(config-if)#ip address 172.16.12.2 255.255.255.0
R2(config-if)#tunnel source GigabitEthernet0/0
R2(config-if)#tunnel destination 192.168.12.1
R2(config-if)#tunnel protection ipsec profile IPSEC_PROFILE

That’s all we need.

Disable Smart Defaults

Optionally, you can disable the smart defaults if you want. Since we configure everything manually, you might have a good reason not to use smart defaults. You can disable them by adding no in front of them:

R1 & R2
(config)#no crypto ikev2 policy default
(config)#no crypto ipsec profile default
(config)#no crypto ipsec transform-set default
(config)#no crypto ikev2 proposal default

When you disable a default, it loses all user configuration. You can re-enable a default by using the command again. For example: crypto ikev2 proposal default will re-enable the default IKEv2 proposal and restores the default values.

Verification

Let’s verify our work. First, I send some pings to the other end of the tunnel to trigger our VPN:

R1#ping 172.16.12.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.12.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 5/5/7 ms

Our pings are working, but to be sure let’s try some IKEv2 and IPSec show commands.

IKEv2

Let’s check out our IKEv2 policy:

R1#show crypto ikev2 policy 

 IKEv2 policy : IKEV2_POLICY
      Match fvrf  : global
      Match address local : any 
      Proposal    : IKEV2_PROPOSAL 

 IKEv2 policy : default Disabled

This tells me the name of our policy and the proposal it uses, and it also shows us that the default policy is disabled. Let’s take a closer look at our proposal:

R1#show crypto ikev2 proposal 
 IKEv2 proposal: IKEV2_PROPOSAL
     Encryption : AES-CBC-256
     Integrity  : SHA256
     PRF        : SHA256
     DH Group   : DH_GROUP_3072_MODP/Group 15
 IKEv2 proposal: default Disabled

Above, we see our proposal and it also tells us that the default proposal is disabled. Let’s check our profile:

R1#show crypto ikev2 profile

IKEv2 profile: IKEV2_PROFILE
 Ref Count: 5
 Match criteria: 
  Fvrf: global
  Local address/interface: none
  Identities: 
   fqdn R2.NWL.LAB
  Certificate maps: none
 Local identity: fqdn R1.NWL.LAB
 Remote identity: none
 Local authentication method: pre-share
 Remote authentication method(s): pre-share
 EAP options: none
 Keyring: IKEV2_KEYRING
 Trustpoint(s): none
 Lifetime: 86400 seconds
 DPD: disabled
 NAT-keepalive: disabled
 Ivrf: none
 Virtual-template: none
 mode auto: none
 AAA AnyConnect EAP authentication mlist: none
 AAA EAP authentication mlist: none
 AAA Accounting: none
 AAA group authorization: none
 AAA user authorization: none

The output above gives us an overview of the identities and keyring we use. Now to the important part; do we have an SA?

R1#show crypto ikev2 sa detailed 
 IPv4 Crypto IKEv2  SA 

Tunnel-id Local                 Remote                fvrf/ivrf            Status 
1         192.168.12.1/500      192.168.12.2/500      none/none            READY  
      Encr: AES-CBC, keysize: 256, PRF: SHA256, Hash: SHA256, DH Grp:15, Auth sign: PSK, Auth verify: PSK
      Life/Active Time: 86400/879 sec
      CE id: 1001, Session-id: 1
      Status Description: Negotiation done
      Local spi: 40BFB27B5A1863C2       Remote spi: E894779083360034
      Local id: R1.NWL.LAB
      Remote id: R2.NWL.LAB
      Local req msg id:  0              Remote req msg id:  2         
      Local next msg id: 0              Remote next msg id: 2         
      Local req queued:  0              Remote req queued:  2         
      Local window:      5              Remote window:      5         
      DPD configured for 0 seconds, retry 0
      Fragmentation not  configured.
      Dynamic Route Update: disabled
      Extended Authentication not configured.
      NAT-T is not detected  
      Cisco Trust Security SGT is disabled
      Initiator of SA : No

 IPv6 Crypto IKEv2  SA

Excellent. We have an IKEv2 SA. You can also use this command which gives a similar output:

R1#show crypto ikev2 session detailed
 IPv4 Crypto IKEv2 Session 

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

Tunnel-id Local                 Remote                fvrf/ivrf            Status 
1         192.168.12.1/500      192.168.12.2/500      none/none            READY  
      Encr: AES-CBC, keysize: 256, PRF: SHA256, Hash: SHA256, DH Grp:15, Auth sign: PSK, Auth verify: PSK
      Life/Active Time: 86400/896 sec
      CE id: 1001, Session-id: 1
      Status Description: Negotiation done
      Local spi: 40BFB27B5A1863C2       Remote spi: E894779083360034
      Local id: R1.NWL.LAB
      Remote id: R2.NWL.LAB
      Local req msg id:  0              Remote req msg id:  2         
      Local next msg id: 0              Remote next msg id: 2         
      Local req queued:  0              Remote req queued:  2         
      Local window:      5              Remote window:      5         
      DPD configured for 0 seconds, retry 0
      Fragmentation not  configured.
      Dynamic Route Update: disabled
      Extended Authentication not configured.
      NAT-T is not detected  
      Cisco Trust Security SGT is disabled
      Initiator of SA : No
Child sa: local selector  192.168.12.1/0 - 192.168.12.1/65535
          remote selector 192.168.12.2/0 - 192.168.12.2/65535
          ESP spi in/out: 0xF653765B/0xD480A04F  
          AH spi in/out: 0x0/0x0  
          CPI in/out: 0x0/0x0  
          Encr: AES-CBC, keysize: 256, esp_hmac: SHA256
          ah_hmac: None, comp: IPCOMP_NONE, mode tunnel

 IPv6 Crypto IKEv2 Session

When it comes to IKEv2, everything looks good.

IPSec

Let’s dive into IPSec. We’ll check our profile:

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