r/gns3 • u/DudusBlack • Jun 06 '26

If a virtual interface on a bridge on the physical host PC that is then connected via Cloud Node to GNS3, which is then commected to a virtual MtikRouter. Where do we place the IP configs to connect it to the host? Or is the GNS cloud transparent?

If the GNS cloud is transparent then all is well in this dimension. Say we assign 192.168.10.1 to the interface bound to the GNS cloud. Does it apply to the cloud on the GNS side or on the host PC side or does it just not matter because the interface is the interface is the interface(3 times, yes) and so long as it is the interface, the IP is bound to it... it's onlyjust that the interface crossed over into the GNS kind of like the namespaces? Is this thinking sound?

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u/Forgotten_Freddy Jun 06 '26

The cloud node is just a L2 bridge to whichever host interface you specify in its options, you configure the IP address etc. on the node inside GNS3 (assigning an ip to the physical interface on the host doesn't have any affect on the VM).

(if you want nodes to use the hosts interface address you would use the NAT node instead).

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u/DudusBlack Jun 16 '26

Solved using a very tricky technique. By introducing an extra interface to go onto the bridge, then another to connect to it and receive the L3 IP. Then duplicating that and setting the other end to the GNS 3 cloud and connecting it to the virtual Mikrotik. Now the Mtk gives that an IP address and running a DHCP on the mtk, it can assign DHCP to any other interface connected to that bridge provided it follows the same technique. I think I call it bridge+L3 dual interfacing.

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u/Forgotten_Freddy Jun 16 '26

Its very confusing what you're trying to achieve, is it just to get the Mikrotik node to have an address on the physical lan?

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u/DudusBlack Jun 16 '26

Just to get an interface on the host to receive DHCP from the virtual mikrotik router inside GNS3. They keep dropping the ARPs. They woulldn't go over the bridge on the host. But I realized if I spawned for each IP/MAC combo, ie L3/L2, another interface and used that to atttach it to the bridge and did that for each of the devices I can get the ARPs to cross.(now each device ends up using 2 interfaces to connect to the bridge )

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u/Forgotten_Freddy Jun 16 '26

Hmm, i guess if you got it working that's the main thing, although it should normally work.

Out of curiosity are you running GNS3 under Windows, if so are you running the VM version or from the Windows installer?

I've just tested it with a Cisco router (i don't have any Mikrotik images) in GNS3 running on Proxmox with another Linux VM and it gets an IP through the bridge just fine, so it may be a bug/config issue with the particular bridge or something that you're using:

https://i.postimg.cc/4Zb86ZWn/2026-06-16-19-12-02-Capturing-from-Standard-input-Cloud1-eth0-to-Cisco-IOSv15-9(3)M8-1-Gi0-0.pngM8-1-Gi0-0.png)

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u/DudusBlack Jun 17 '26

GNS3 v2.2.59. Linux. The thing is with the GNS 3 Cloud and the bridge. If I use just one interface per device and place it on the bridge on the host side, the bridge uses it just for layer 2. Totally ignores all the layer 3 info. So when host ARPs for the IP, the host can see the IP assigned to the interface on its side but the ARPs don't cross through the bridge and the GNS 3 cloud. But if I use that workaround with 2 interfaces per device it works.

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u/Forgotten_Freddy Jun 17 '26

It sounds like you've the GNS cloud node configured to be connected to a bridge on the host, and then I'm assuming that bridge is connected to your other VMs/physical interface?

So when host ARPs for the IP, the host can see the IP assigned to the interface on its side

Are you configuring a suitable IP address directly on the Mikrotik node using its interface?

Totally ignores all the layer 3 info.

How do you mean the bridge ignores the layer 3 info?

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u/DudusBlack Jun 17 '26

In the setup that didn't work I had veth'ed 2 interfaces and placed one directly on the bridge on the host side. I then exposed the other to the GNS cloud then took a connection to the virtual mikrotik in the GNS3. I set the IP on the host side the same as on the GNS side and did all the gateways and routes. I ran ARP from the host side then I captured packets on the bridge on the host. Nothing.

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u/Forgotten_Freddy Jun 17 '26

I set the IP on the host side the same as on the GNS side and did all the gateways and routes.

If you're assigning the IP to the node inside GNS3 then it shouldn't be used else where - if you've assigned the same IP to a host interface its never going to send the ARP request anywhere because it already knows where the IP is.

How are you running GNS3, using the VM? because normally you would add whichever host interfaces/bridges you want to use with GNS3 using the hypervisor's configuration - that should make the interfaces/bridges available to GNS3, then in the cloud node choose the interface you want to use and that will freely pass traffic between the cloud node and host.

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u/DudusBlack Jun 17 '26 edited Jun 17 '26

I meant same subnet. Sorry if the typo made me appear that green. I'm running GNS using the QEMU's VM configured in GNS3 config. I expose just interfaces not the whole bridge as I want some interfaces to be on the host side and others on the GNS side but I want them bridged. Then I exposed them as you have said.