This guide explains how to set up a Dynamic Multipoint VPN using
Setting Up the Certificate Authority
Install the Certificate Authority (CA) tool on a secure host:
apk add dmvpn-ca
Configure the CA by editing
/etc/dmvpn-ca.conf. In this example, the following
configuration is used:
hub: hosts: - hubs.example.com subnets: - '10.0.0.0/8' - '172.18.0.0/16' - 'fd00::/32' crl: dist-point: 'http://crl.example.com/dmvpn-ca.crl' lifetime: 1800 renewal: 1200
hosts attribute specifies the IPv4 addresses of the hubs or DNS name(s)
resolving to those. In this example, it is assumed that resolution of
hubs.example.com yields an A record for each hub.
subnets attribute is a list of subnets used in the VPN. This should
include the address ranges of all sites and the GRE tunnel addresses. In this
example, the following IP address scheme is used:
crl object should be left out unless the CRL distribution point will be
|Hub GRE address||172.18.0.<hub id>||fd00::<hub id>|
|Site VPNc GRE address||172.18.<site id>.<vpnc id>||fd00::<site id>:<vpnc id>|
|Site subnet||10.<site id>.0.0/16||fd00:0:<site id>::/48|
IPv6 addresses can be left undefined if only IPv4 is used in the VPN.
After setting up the CA configuration, generate the root key and certificate:
dmvpn-ca root-cert generate
Create the configuration for hubs and sites. In this example, there are two hubs and two sites. Each site has two VPN concentrators (VPNcs) for redundancy.
dmvpn-ca hub create dmvpn-ca gre-addr add 172.18.0.1 hub 1 dmvpn-ca gre-addr add fd00::1 hub 1 dmvpn-ca hub create dmvpn-ca gre-addr add 172.18.0.2 hub 2 dmvpn-ca gre-addr add fd00::2 hub 2 dmvpn-ca site add FIN dmvpn-ca subnet add 10.1.0.0/16 site FIN dmvpn-ca subnet add fd00:0:1::/48 site FIN dmvpn-ca vpnc create site FIN dmvpn-ca gre-addr add 172.18.1.1 site FIN vpnc 1 dmvpn-ca gre-addr add fd00::1:1 site FIN vpnc 1 dmvpn-ca vpnc create site FIN dmvpn-ca gre-addr add 172.18.1.2 site FIN vpnc 2 dmvpn-ca gre-addr add fd00::1:2 site FIN vpnc 2 dmvpn-ca site add SWE dmvpn-ca subnet add 10.2.0.0/16 site SWE dmvpn-ca subnet add fd00:0:2::/48 site SWE dmvpn-ca vpnc create site SWE dmvpn-ca gre-addr add 172.18.2.1 site SWE vpnc 1 dmvpn-ca gre-addr add fd00::2:1 site SWE vpnc 1 dmvpn-ca vpnc create site SWE dmvpn-ca gre-addr add 172.18.2.2 site SWE vpnc 2 dmvpn-ca gre-addr add fd00::2:2 site SWE vpnc 2
Finally, generate the keys and certificates for the hubs and VPNcs:
dmvpn-ca cert generate
This commands generates a PFX file for each hub and VPNc, for example:
# ls FIN_1.9D6JLGHlLmTG4bVR.pfx SWE_1.caN3yapMTpZbIVP4.pfx _1.hy62AqLIUJcFuT1U.pfx FIN_2.fXbw4HwqkLXlIbtk.pfx SWE_2.0BElySor2L8fm6e2.pfx _2.cDLUvB8XALBkD2vP.pfx
The encrypted file contains the individual certificate, the corresponding private key, and the root certificate. The password is embedded in the file name. The file should be renamed when using out-of-band delivery for the password.
In this example, the CA host serves also as the master CRL distribution point.
In addition, there may be other distribution points which periodically mirror
the CRL from the CA host. It is assumed that
ca.example.com resolves to the
CA host and
crl.example.com resolves to the IP addreses of all distribution
Install the CRL distribution point package on the target host (CA host or mirror):
apk add dmvpn-crl-dp
If setting up a mirror, configure the master distribution point by creating a
/etc/dmvpn-crl-dp.conf with the following contents:
Activate CRL distribution by executing the following commands:
dmvpn-crl-update rc-update add lighttpd rc-service lighttpd start
Setting Up a Hub
Warning: This procedure will automatically set up the
awall. If you require any additional rules, such as allowing SSH access
to the host, you should configure those first. The easiest way to do so is to
apk add awall-policies setup-firewall
dmvpn package on the host to be configured as a DMVPN hub. It is
assumed that the network configuration of the host is already in place.
apk add dmvpn
Execute the setup tool using the hub’s PFX file, answering the questions prompted. The password is deduced from the file name unless renamed. Enter the prefix lengths that uniquely identify the site. The default values are valid for this example. The prefix length may vary among the sites, in which case the maximum length should be given.
setup-dmvpn <pfx file>
The hub is now operational and its firewall has been set up. Firewall for IPv6
ip6tables) is set up by
setup-dmvpn only if IPv6 addresses are defined for
the VPN. (
setup-firewall sets it up if IPv6 is enabled in the kernel.)
Setting Up a Site VPNc (Spoke)
dmvpn package on the host to be configured as a DMVPN spoke. It
is assumed that the host is already configured as a router to the site subnet.
apk add dmvpn
Execute the setup tool using the spoke’s PFX file, answering the questions prompted. The password is deduced from the file name unless renamed.
setup-dmvpn <pfx file>
The spoke is now operational. Firewall rules are updated automatically if they
are managed using
Backing Up the CA
It may be a good idea to back up the configuration and the state of the CA. This section describes one way to do so.
If you are using a firewall, allow outgoing SSH connections to the
backup host. If you set it up with
setup-firewall, you can do this by
adp-ssh-client policy. This will allow SSH connections
to any host, though.
awall enable adp-ssh-client awall activate
Generate an SSH key pair on the CA host:
Append the generated public key to the list of the authorized keys on
the backup host. Install
rsync on the backup host:
apk add rsync
in-sync on the CA host:
apk add in-sync
Configure the backup host as the target in the CA host’s
Start the synchronization service on the CA host:
rc-update add in-sync rc-service in-sync start
In case the original CA host is lost, you may convert the backup host to a new CA host by installing the CA tool:
apk add dmvpn-ca
If the CA host was serving as the master CRL distribution point, you need to set up that function as well.