Can connect via VPN, but can't access AFP server on same Xserve

Your server needs to have more than 1 IP address for you to access its resources using VPN. It does not matter if it is a private or public IP. You don't need to use a separate interface, just setting up an alias will do.

System Preferences - Network. Press the '+' button, select your already used Ethernet interface, enter something like 'VPN access' for the Service Name and press Create. Then configure it by entering the IP address and netmask ONLY. Everything else is read automatically from the base configuration.

Open Terminal and type ifconfing to see the configuration. You should see two IP addresses listed on the Ethernet interface.

Whichever IP you connect to, use the other one to access local resources on the server. For consistency reasons it would make more sense to make the VPN connection to the alias IP and then connect to the familiar server IP to access local resources.

"I am able to successfully connect to our network via the VPN with Mac OS X 10.5.2 client (on two different machines) using L2TP through our network's firewall (on a Netopia T1 router; UDF ports 500 and 4500 and IP Protocol 50 and 51 are open) using a shared secret."

I suspect you mean UDP ports and you might need UDP port 1701 open too.

You only need IP protocol 50 (ESP), protocol 51 (AH) isn't used. And ESP is only used when client and server isn't behind NAT (when NAT is used only the UDP ports are used).

"Unsupported protocol 0x8057 received"

This is usually seen when you can't get GRE through but since you don't use PPTP I can't be sure why this is registered in the logs. Sometimes when connecting using PPTP you have to disconnect and then reconnect for everything to work - you might try this for L2TP too.

But if you already can reach services on any LAN nodes through the VPN I wouldn't bother with it.

As you have a firewall in front of the server you need a second alias IP on the server that you can use to get at the services running on the server through the VPN. The firewall blocks all ports protocols not opened - that's why you can't use the server main IP even if the VPN is up.

The netmask is used by all nodes to determine how big your subnet is: what part of the IP number is the network number and what range the node number is in => really: should traffic be directed to a node on the same LAN or sent directly to the gw/router for forwarding.

What you can't do is connect from a NATed network to another NATed network that both are using the same network number. (That's why people should stay away from using the "default" 192.168.0.0/24 and 192.168.1.0/24 networks for VPN server LANs).

Try your settings at http://www.jodies.de/ipcalc to see what I mean.


"...lists the router as having the IP address of the XServe (rather than the router on the network). Is that normal?"

Yes. The VPN server is the VPN gw/router.


"The firewall for the 10.5.2 server is not running (but will be once I get this all working)."

If you already have a firewall in front of your servers that is a bit redundant.


"--No network routing definitions have been set up."
"I'm hoping I don't need to have the XServe run DNS as an internal LAN DNS server"

You need routing definitions if you want to setup a split tunnel VPN or all traffic is routed through the VPN when connected. The VPN becomes the default gw.

Without ipforwarding ON in the server you can only reach nodes on the server LAN - not Internet.

DNS is needed for your servers forward and reverse names/IPs for advanced services but doesn't need to run in any of your own servers.


If you decide to do a split tunnel VPN config (adding public and private routing definitions) a reachable DNS IP for VPN clients (in VPN config on server) is needed for VPN clients or they can't use names to find anything. To reach this DNS IP if public/not on your server LAN, you need your server to forward IP DNS lookups and have a routing definition for it.

A split tunnel VPN only send traffic for your server LAN through the VPN and all other traffic directly to the local gw/router (Internet).

"It does not matter if it is a private or public IP" - yes it does.

You only need a second IP if the server use only public IPs (and have a firewall running - which you should).

Message was edited by: Leif Carlsson

This is the first time I read that an alias IP address should have netmask 255.255.255.255. For years we have had our company VPN server running on Windows Server having an alias IP address and netmask for both IP addresses was 255.255.255.0. I assumed that it would be the same for OS X and this is how I have configured our new XServer and the VPN actually works. So I am a bit confused now. Maybe somebody with more knowledge can shed some light.

"I made a duplicate of my en0 settings with a new second public IP and still can't connect."

You only need IP number and netmask.


"I also duplicated my firewall rules for the second public IP to match the original IP on en0."

In the Netopia router? This second server IP should have no access from Internet, only from server LAN/IP/VPN.


"is necessary also to make sure that the Subnet Mask setting for all but one of the ports is 255.255.255.255. This will prevent conflicts in the routing tables."

Never had any trouble with using the same subnetmask as the "real" interface.


"On a headless Xserve, the same thing can be accomplished with the IPAliases startup item."

I have only used the Network pref pane to set this up and it works.


"Should the subnet mask for the second public IP address be 255.255.255.255"

Hm... does maybe not matter but 255.255.255.128 should work fine.

Your second serve IP is in the right half of your network (1-126 or 129-254)? Same as the first one?

And you connect to the real IP with the VPN and then use the second one to get at services in the server?


"I was reserving the second ethernet port on the Xserve for lights out management, but I'm thinking maybe I should just use that port for the VPN. Would that be an easier fix?"

No, you would need to enable the firewall and NAT and force the second interface up. At least if you want to be able to reach Internet from a VPN connection. LOM can use the first port (need to be connected to the network).

(Your LAN switch haven't got LACP capability?)

Do you have set firewall rules allowing you to connect to the second IP address? I cannot think of another reason right now. Look at the VPN log and see if there is any activity at all when you connect to the second IP. If not, then I'd say the firewall rules are not in place.

Hmm... I have not really tried L2TP, only PPTP. Maybe this a specific issue related to L2TP :-S