Cisco EZVPN with IOS Router and ASA

I had an interesting request come across my desk, where I needed to configure a site-to-site VPN for some internet connected devices, but the devices were not allowed to connect internally to our network. So basically, I needed to tunnel the internet traffic back to our headend without allowing access to the internal network. The remote location also wouldn’t have a static IP. Having used EZVPN in the past, I figured this would be another great use case. Unfortunately I spent way too many hours trying to find a good example of how to get this setup working, so I figured I’d share my config for anyone else who may be struggling with a similar setup.

Diagram

EZVPN with IOS and ASA

IOS Router Config (EZVPN Client)

crypto ipsec client ezvpn ez
 connect auto
 group MyTunnelGroup key MySecretKey
 mode client
 peer 10.10.10.1
 username MyVPNUser password MyPassword
 xauth userid mode local
!
interface Fa0/0
 description WAN Interface
 ip address dhcp
 crypto ipsec client ezvpn ez
!
interface Fa0/1
 description LAN Interface
 ip address 192.168.0.1 255.255.255.0
 crypto ipsec client ezvpn ez inside
!

The first section defines the properties for the EZVPN connection, and there are 3 items that need special attention:

  1. The group and key you configure here will match the TunnelGroup name and IKEv1 key you configure on the ASA
  2. The username and password are also defined on the ASA. This is the actual user that is being authenticated.
  3. The xauth mode needs to be configured as local so the router doesn’t have to prompt for credentials.

Other items to note:

  1. There are three modes for EZVPN, Client, Network Extension, and Network Plus. If this were a true L2L VPN, I’d use Network Extension or Network Extension Plus so that there was direct IP-IP connectivity between hosts on either side of the VPN. Since I don’t need that, I’m configuring Client mode which is similar to a PAT for all client traffic.
  2. The peer IP will be the outside address of your EZVPN server.

ASA Configuration (EZVPN Server)

access-list EZVPN-ACL standard deny 10.0.0.0 255.0.0.0
access-list EZVPN-ACL standard permit any4
!
group-policy MyGroupPolicy internal
group-policy MyGroupPolicy attributes
 dns-server value 8.8.8.8
 vpn-access-hours none
 vpn-simultaneous-logins 3
 vpn-idle-timeout 30
 vpn-session-timeout none
 vpn-filter value EZVPN-ACL
 vpn-tunnel-protocol ikev1
 group-lock none
 split-tunnel-policy tunnelall
 split-tunnel-all-dns enable
 vlan none
 nac-settings none
!
username MyVPNUser password MyPassword
username MyVPNUser attributes
 vpn-group-policy MyGroupPolicy
!
tunnel-group MyTunnelGroup type remote-access
tunnel-group MyTunnelGroup general-attributes
 default-group-policy MyGroupPolicy
tunnel-group MyTunnelGroup ipsec-attributes
 ikev1 pre-shared-key MySecretKey

The Tunnel Group defines the preshared key for the connection that was referenced in the group MyTunnelGroup key MySecretKey command on the client. The Tunnel Group config also points to a Group Policy that will control the policy for the tunnel. I created a new policy, but you could also use the default DfltGrpPolicy if it fit your needs.

Conclusion

The beautiful thing about EZVPN is that all of the policy aspects are controlled at the Server side. So while the current requirement is to block access to internal resources, I could easily change that on the server side without worrying about messing up the config on the client and bringing the tunnel down.

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