[Openswan Users] Firewall rules for openswan behind NAT

Fred Weston fred.weston at lpga.com
Thu Nov 21 18:24:06 UTC 2013

net.ipv4.ip_forward=1 is present, net.ipv4.conf.default.rp_filter is set to 1, not 0.  None of the other values are in the file.

Could you please help me understand what those values do?

-----Original Message-----
From: users-bounces at lists.openswan.org [mailto:users-bounces at lists.openswan.org] On Behalf Of Paul Wouters
Sent: Thursday, November 21, 2013 12:09 PM
To: users at openswan.org
Subject: Re: [Openswan Users] Firewall rules for openswan behind NAT

On Thu, 21 Nov 2013, Fred Weston wrote:

[ cut fred from reply, as it generates errors - guess he might see this on the list itself ]

> Each openswan box does only have one interface.  On that interface it has a 10.x.x.x IP address which serves as both access to the local subnet as well as Internet access via 1:1 NAT to a public IP.

Then check your /etc/sysctl.conf settings to ensure they contain:

net.ipv4.ip_forward = 1
net.ipv4.conf.default.rp_filter = 0
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.send_redirects = 0 net.ipv4.icmp_ignore_bogus_error_responses = 1

The linux kernel with xfrm is known to do really stupid icmp redirects when used with only a single interface.

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