8.2.2. IPsec Interfaces

With Red Hat Enterprise Linux it is possible to connect to other hosts or networks using a secure IP connection, known as IPsec. For instructions on setting up IPsec using the Network Administration Tool (system-config-network), refer to the chapter titled Network Configuration in the System Administrators Guide. For instructions on setting up IPsec manually, refer to the chapter titled Virtual Private Networks in the Security Guide.
The following example shows the ifcfg file for a network-to-network IPsec connection for LAN A. The unique name to identify the connection in this example is ipsec1, so the resulting file is named /etc/sysconfig/network-scripts/ifcfg-ipsec1.
TYPE=IPsec
ONBOOT=yes
IKE_METHOD=PSK
SRCNET=192.168.1.0/24
DSTNET=192.168.2.0/24
DST=X.X.X.X
In the example above, X.X.X.X is the publicly routable IP address of the destination IPsec router.
Below is a listing of the configurable parameters for an IPsec interface:
  • DST=<address>, where <address> is the IP address of the IPsec destination host or router. This is used for both host-to-host and network-to-network IPsec configurations.
  • DSTNET=<network>, where <network> is the network address of the IPsec destination network. This is only used for network-to-network IPsec configurations.
  • SRC=<address>, where <address> is the IP address of the IPsec source host or router. This setting is optional and is only used for host-to-host IPsec configurations.
  • SRCNET=<network>, where <network> is the network address of the IPsec source network. This is only used for network-to-network IPsec configurations.
  • TYPE=<interface-type>, where <interface-type> is IPSEC. Both applications are part of the ipsec-tools package.
Refer to /usr/share/doc/initscripts-<version-number>/sysconfig.txt (replace <version-number> with the version of the initscripts package installed) for configuration parameters if using manual key encryption with IPsec.
The racoon IKEv1 key management daemon negotiates and configures a set of parameters for IPSec. It can use preshared keys, RSA signatures, or GSS-API. If racoon is used to automatically manage key encryption, the following options are required:
  • IKE_METHOD=<encryption-method>, where <encryption-method> is either PSK, X509, or GSSAPI. If PSK is specified, the IKE_PSK parameter must also be set. If X509 is specified, the IKE_CERTFILE parameter must also be set.
  • IKE_PSK=<shared-key>, where <shared-key> is the shared, secret value for the PSK (preshared keys) method.
  • IKE_CERTFILE=<cert-file>, where <cert-file> is a valid X.509 certificate file for the host.
  • IKE_PEER_CERTFILE=<cert-file>, where <cert-file> is a valid X.509 certificate file for the remote host.
  • IKE_DNSSEC=<answer>, where <answer> is yes. The racoon daemon retrieves the remote host's X.509 certificate via DNS. If a IKE_PEER_CERTFILE is specified, do not include this parameter.
For more information about the encryption algorithms available for IPsec, refer to the setkey man page. For more information about racoon, refer to the racoon and racoon.conf man pages.