Layer 2 between sites
Sometimes two servers in different places need to behave as if they share one network segment — same subnet, broadcasts and all. A layer-2 link between sites gives you that, with some real caveats worth knowing first.
Most links between sites work at layer 3 — they route between two different subnets. A layer-2 extension instead makes two locations share the same subnet, as if a single switch spanned both. It is powerful and occasionally necessary, and it is also a good way to spread one site’s problems to another.
When you actually need it
- Software that insists two nodes be on the same subnet — some clustering and failover setups
- Moving a service between sites without changing its IP
- A VLAN that must appear identical in two places — see VLANs and tagged interfaces
How it is done
VXLAN (or a provider L2VPN) encapsulates layer-2 frames and carries them across a routed network between sites. To the servers it looks like one segment; underneath it is tunnelled. We can provide this between locations on our network — see connecting your own servers privately.
Broadcasts travel too
A shared segment means shared broadcast traffic — and a broadcast storm or a loop at one site now hits both. Layer 2 does not contain faults the way routing does; a problem that would stay local on an L3 link becomes everyone’s problem on an L2 one. That containment is the main reason to prefer L3 when you can.
Latency changes behaviour
Protocols that assume a LAN assume LAN latency. Stretch the segment across even a short distance and that assumption weakens; across a long one it breaks. Layer-2 extension does not make two distant sites local — the speed of light still applies. See latency and bandwidth.
Prefer layer 3 unless you cannot
If the requirement is really “these services must talk to each other”, a routed link or a WireGuard VPN is simpler, safer and scales better. Reach for layer 2 only when something genuinely demands a shared subnet — and tell us what, so we build the right thing.
Still stuck? Mail support@novogara.com — an engineer answers, at any hour. Back to the knowledge base