NETKEY IPsec and ARP

Posted by Shawn J. Goff on Server Fault See other posts from Server Fault or by Shawn J. Goff
Published on 2012-03-23T13:50:54Z Indexed on 2012/03/23 17:31 UTC
Read the original article Hit count: 410

Filed under:

routing

|

ipsec

|

arp

I'm wondering if I have the correct routing setup for an IPsec tunnel. I have control over the IPsec endpoints and the hosts connected to one side. These hosts are connecting to the tunnel so that they have access to the network on the other side of what I will call the IPsec server. I don't have control of the network upstream of this server.

Normally, the IPsec server will not respond to ARP requests for the hosts on the other side of the tunnel. So when a packet arrives for one of my hosts the server gets ARP requests, but the upstream router gets no response, and cannot construct the ethernet frame to send me the packets. If I was using one of the swan stacks, I would have a separate interface, and I'd probably just need to turn on proxyarp, but I'm using NETKEY, which doesn't use a separate interface for the tunnel.

To solve the problem for now, I have added an eth0.5 vlan to the IPsec server, turned on proxyarp for that interface, and added all routes my hosts addresses to that interface so that it will respond to those ARP requests (and will therefore get relevant packets routed to it).

This works, but it feels wrong. What is the correct way to get the upstream router to send me the traffic for these hosts?

© Server Fault or respective owner

Related posts about routing

Issue with Url Routing(System.Web.Routing) 3.5 in Godaddy...(non-MVC App)

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi, I am using System.Web.Routing namespace in Asp.Net 3.5 non-mvc app. Its working perfect in local machine but I tried deploying in godaddy server it doesnt work Does anyone has experiece with them ? Thanks in Advance.. Deepu >>> More
cakephp routing problem, plugin routing works but not others

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm having a strange routing problem with a site I just uploaded, and I've made a number of changes to test what's happening. It doesn't make any sense. My setup is: - I'm using one plugin, which I've included all the routing in the routes.php file. - I've also included the routes for two other… >>> More
Routing in php vs routing in rails..

as seen on Stack Overflow - Search for 'Stack Overflow'
I was working on php from past 1 yr and now a days i m learning rails. In rails:-- Routing takes an incoming URL and decodes it into a set of parameters that are used by Rails to dispatch to the appropriate controller and action for example rs.recognize_path "/blog/show/123" {:controller=>"blog"… >>> More
Why isn't ICMP routing with iptables nat routing

as seen on Server Fault - Search for 'Server Fault'
I'm using iptables on Ubuntu server to route a public IP to a private IP. I want to nat all traffic, including 80, 443 and ICMP. However, it appears that ICMP isn't routing. I have a steady ping going to the public IP and it never stops, even with NAT pointing to a bogus IP. Here are the rules… >>> More
An Introduction to ASP.NET Web API

as seen on West-Wind - Search for 'West-Wind'
Microsoft recently released ASP.NET MVC 4.0 and .NET 4.5 and along with it, the brand spanking new ASP.NET Web API. Web API is an exciting new addition to the ASP.NET stack that provides a new, well-designed HTTP framework for creating REST and AJAX APIs (API is Microsoft’s new jargon for a service… >>> More

Related posts about ipsec

Ipsec reload fails to load ipsec.conf Strongswan 5.0

as seen on Server Fault - Search for 'Server Fault'
I am having trouble configuring a connection to an Android device using a fedora 17 linux machine and strongSwanv5.0.1dr2. I have made some progress but when I try adding the configuration to support xauth authentication I receive an error when I try to reload the configuration file. I get a similar… >>> More
Specify IPSEC port range using ipsec-tools

as seen on Server Fault - Search for 'Server Fault'
Is it possible to require IPSEC on a port range ? I want to require IPSEC for all incoming connections except a few public ports like 80 and 443, but don't want to restrict outgoing connections. My SPD rules would look like: spdadd 0.0.0.0/0 0.0.0.0/0[80] tcp -P in none; spdadd 0.0.0.0/0 0.0.0.0/0[443]… >>> More
Connecting debian and windows via IPsec VPN with Racoon and ipsec-tools

as seen on Server Fault - Search for 'Server Fault'
I've some trouble with the IPsec configuration on my debian server (6 squeeze). This server should connect via IPsec VPN to an windows server, which is protected by an firewall. I've used racoon and ipsec-tools and this tutorial http://wiki.debian.org/IPsec. However, I am not quite sure, if this… >>> More
ASA hairpining: I basicaly want to allow 2 spokes to be able to communicate with each other.

as seen on Server Fault - Search for 'Server Fault'
ASA Spoke to Spoke Communication I have been looking at spke to spoke comms or "hairpining" for months and have posted on numerouse forums but to no avail. I have a Hub and spoke network where the HUB is an ASA Firewall version 8.2 * I basicaly want to allow 2 spokes to be able to communicate with… >>> More
Can't get the L2TP IPSEC up and running

as seen on Server Fault - Search for 'Server Fault'
i have an Ubuntu 11.10 (oneiric) server running on a ReadyNAS. Im planning to use this to accept ipsec+l2tp connections through a router. However, the connection is failing somewhere half through. Using Openswan IPsec U2.6.28/K3.0.0-12-generic and trying to connect with an iOS 5 iPhone 4S. This is… >>> More