An Ethernet Private Line (EPL) gives you a whole port at each end, dedicated to one connection, and carries whatever you send through it untouched, including your own VLAN tags. An Ethernet Virtual Private Line (EVPL) lets one physical port carry several separate connections, each identified by a VLAN, so a head office can reach many branches through a single port. EPL is simpler and more transparent. EVPL is more efficient when one site talks to many.
Both are private Layer 2 links that never touch the public internet, and both are sold as "point-to-point Ethernet." The difference shows up when you connect site number three, and again when you look at how many ports you are paying for at head office.
The vocabulary, briefly
These terms come from the MEF, the industry body that defines carrier Ethernet services. You will see them on quotes:
- UNI (user network interface): the physical port the carrier hands you at a site.
- EVC (Ethernet virtual connection): the logical connection between two or more UNIs. It is the "circuit" in everything but name.
- E-Line: a point-to-point service type. EPL and EVPL are both kinds of E-Line.
- E-LAN: multipoint, where every site can reach every other, like a private switch across the city. Its versions are EP-LAN and EVP-LAN.
- E-Tree: rooted multipoint, where branches reach a hub but not each other.
EPL and EVPL side by side
| EPL | EVPL | |
|---|---|---|
| Connections per port | One EVC per UNI; the port belongs to that link | Several EVCs on one UNI |
| How traffic is identified | Everything entering the port goes to the other end | Each EVC is mapped to one or more of your VLAN IDs |
| Your VLAN tags | Carried transparently, untouched | Used to pick the EVC, so they must be coordinated with the carrier |
| Control protocols (such as spanning tree or LACP) | Often carried through | Often filtered or limited; check |
| Bandwidth | A committed rate up to the port speed | A committed rate per EVC, sharing the port |
| Best for | Two sites that need to behave like one; a small number of links | Hub and spoke: one head office or data centre, several branches |
How EPL behaves
With EPL, the carrier behaves like a very long patch cable. Whatever frames you put into the port at site A come out of the port at site B, with your VLAN tags intact. You can run many VLANs across it without telling the carrier, and many carriers will pass through control protocols such as link aggregation or spanning tree, so the two sites can act as one network.
The cost of that simplicity is ports. If head office needs EPLs to four branches, it needs four UNIs at head office, four router or switch interfaces, and four sets of cross-connects or in-building wiring.
How EVPL behaves
With EVPL, head office gets one UNI, and each branch connection is an EVC mapped to a VLAN. VLAN 101 might go to the Brooklyn warehouse, VLAN 102 to the Queens store, and so on. Your router at head office sees one physical interface with several sub-interfaces, one per branch.
Each EVC carries a bandwidth profile. The main terms are CIR (committed information rate, the bandwidth guaranteed to that EVC) and sometimes EIR (excess information rate, extra bandwidth that may be available but is not guaranteed). The sum of the CIRs has to fit within the hub port, which is the constraint you design around.
The trade-off is coordination. VLAN numbers must be agreed with the carrier, some control protocols will not pass, and adding a branch is a change to a shared port rather than a separate circuit.
A worked example
A hypothetical network to show the design choice. The sites, speeds and requirements are invented, and no prices are implied.
Suppose a company has a head office and data room in Chicago and four branches around the metro. Each branch needs about 200 Mbps to head office for file access, phones and a line-of-business application. Branch-to-branch traffic is minimal.
Option A, four EPLs. Four separate circuits, each with a 1 Gbps port at both ends and a 200 Mbps committed rate. Head office needs four UNIs, so four carrier handoffs and four router ports.
Option B, EVPL. Head office gets one 1 Gbps UNI carrying four EVCs of 200 Mbps each. The four committed rates add up to 800 Mbps, which fits within the 1 Gbps hub port with 200 Mbps of headroom. Each branch has its own UNI with one EVC. Head office needs one carrier handoff and one router port with four sub-interfaces.
Option B saves three ports at head office, and often some monthly cost, depending on how the carrier prices UNIs and EVCs. The catch comes at branch number six: six EVCs of 200 Mbps add up to 1.2 Gbps, more than the hub port. At that point head office needs a 10 Gbps UNI, or the branch rates need to come down. It is a good problem to plan for, not one to discover.
If the branches started exchanging a lot of traffic with each other, EVPL would force it all through head office. That would be the moment to look at E-LAN instead.
The details that trip people up
- MTU. The maximum frame size the carrier will carry. Storage replication and some tunnels need jumbo frames. Ask for the supported MTU on each EVC, in writing.
- Control protocols. If you are relying on LACP, spanning tree, CDP or LLDP passing between sites, confirm what the service carries, drops or processes.
- Class of service. If voice rides the link, ask whether the carrier honours your priority markings, and how many classes it offers.
- Different carriers at different sites. When one site is on carrier X and another on carrier Y, the service may be stitched together at a handoff between them. It can work well, but ask who owns the whole path when something breaks.
- Resilience. A single EPL or EVPL is one path. If losing a branch link matters, plan a second path, perhaps an internet connection with SD-WAN as the backup.
When neither is the right answer
Private Ethernet is not the only way to join sites. Two alternatives often come up:
- SD-WAN over internet circuits. Each site gets dedicated internet or shared fiber, and SD-WAN builds encrypted tunnels between them. It can cost less and adds internet access at each site, at the price of less predictable performance between sites. Our SD-WAN guide goes further, and multi-site business internet covers the broader choice.
- A wavelength. For 10G and above between a few key points, a wavelength service gives full line rate and fixed latency.
Many companies end up with a mix: private Ethernet between head office and the data room, SD-WAN out to smaller branches.
Moving from one to the other later
Networks change. A company that starts with a single EPL between two offices often adds a third site, then a fourth, and finds itself paying for a growing pile of head office ports. Converting to EVPL at that point usually means a new hub UNI, re-tagging traffic on the head office router, and moving each branch across in a planned window. It is not difficult, but it is a project, and some carriers treat each converted link as a new order with a new term.
The reverse happens too. A branch that grows until its EVC needs most of the hub port is often better off on its own EPL, or on a wavelength if it passes 10G. The practical lesson is to ask, before signing, how the carrier handles converting or upgrading a connection mid-term, and whether that restarts the contract.
Checklist before you order
- Map which sites talk to which, and how much. Hub and spoke points to EVPL, site pairs to EPL, full mesh to E-LAN or SD-WAN.
- List the VLANs that must cross each link.
- Decide whether any control protocols must pass between sites.
- Note the MTU your applications need.
- Size the hub port for the branches you expect in two to three years, not just today.
- Decide what happens when a link fails.
Questions to ask your carrier
- Is this EPL or EVPL, and how is my VLAN tagging handled?
- Which Layer 2 control protocols are passed, filtered or processed?
- What MTU is supported on each connection?
- What bandwidth profile applies: committed rate, any excess rate, burst size?
- How many priority classes do you support, and do you honour my markings?
- If a site is off your network, whose network carries that leg, and who handles faults end to end?
- How long does it take to add an EVC to an existing hub port?
Getting your site links priced
EPL and EVPL quotes are only comparable once the ports, committed rates, MTU and class of service line up, which is the work we do when several carriers bid on your addresses. We will also tell you if SD-WAN over internet circuits would do the job for less. See the Ethernet transport page for how we quote it. The quote is free with no obligation, and you usually hear back the same day. Send us your sites, call 478-758-8091 or text (347) 870-0965.
