From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Neal P. Murphy" Subject: Re: Creating a LAN only null routed network (no access to internet) Date: Thu, 13 Aug 2015 02:31:39 -0400 Message-ID: <20150813023139.3d91a82d@playground> References: <55CB462D.6040203@privatedemail.net> <55CC2DD4.6090706@privatedemail.net> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <55CC2DD4.6090706@privatedemail.net> Sender: netfilter-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: netfilter@vger.kernel.org Cc: sillysausage On Thu, 13 Aug 2015 15:10:36 +0930 sillysausage wrote: > It does turn out I will need to buy myself a managed switch at some > point and use VLANs instead of virtual interfaces if I want to assign IP > addresses in this range. Virtual interfaces such as eth0:3 (192.168.3.1) > currently have the same broadcast as eth0 (192.168.1.1) which would mean > this will never work: What happens if you don't use virtual IFs? That is, use multiple primary addresses: ip addr add 192.168.1.1/24 dev eth0 ip addr add 192.168.2.1/24 dev eth0 ip addr add 192.168.3.1/24 dev eth0 The system determines the correct broadcast address to use based on the source address. With correct primary CIDR addresses, you don't need to specify the broadcast address at all. Or does this make your routing impossible to achieve?