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I have a quad NIC. Port 1 goes directly to the switch. I would like ports 2, 3, and 4 to basically function as a hub. Anything connected to them should be assigned a DHCP address from the router, and all traffic will flow through port 1.

I have tried to set up a bridge on ports 2, 3, and 4. I can get them to pass information if I manually set an IP address for each port, but the goal is DHCP.

I have tried setting up a bridge on port 1. This doesn't seem to have any effect.

I have tried using the network connections interface to enable internet connection sharing on ports 2, 3, and 4. This allows devices to connect to ports 2, 3, and 4, but ubuntu assigns them 10.42.0.x addresses.

How do I set up my wired connections in Ubuntu 18.04 so that eno1 connects to a host router, and eno2, eno3, eno4 can provide dhcp addresses forwarded by the router?

2 Answers 2

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You could allow communication across all NICs by enabling IP Forwarding and setting up some iptables rules:

$ sudo net.ipv4.ip_forward = 1
$ sudo vim /etc/sysctl.conf

net.ipv4.ip_forward = 1
$ sudo vim /etc/iptables/rules.v4

*nat
-A POSTROUTING -o eth0 -j MASQUERADE
-A POSTROUTING -o eth1 -j MASQUERADE
-A POSTROUTING -o eth2 -j MASQUERADE
-A POSTROUTING -o eth3 -j MASQUERADE

*filter
-A FORWARD -i eth0 -j ACCEPT
-A FORWARD -i eth1 -j ACCEPT
-A FORWARD -i eth2 -j ACCEPT
-A FORWARD -i eth3 -j ACCEPT
$ sudo iptables --flush && sudo iptables-restore < /etc/iptables/rules.v4
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I would think that bridging eno1, eno2, eno3 and eno4 as br0 is what you are trying to do. Mind you, I have fairly little experience with this kind of complicated stuff, though. Even if it works, it might not be the most efficient solution, but in a LAN that's often not too much of a concern.

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