Can switch pass traffic between devices that don't have MAC addresses

[Ab26]

I have customer that has a special system where the end devices don't have MAC addresses nor IP addresses. The system was previously connected via direct cables (fiber and ethernet). The customer has now requested to connect these devices to Cisco L2 switches.

Upon connecting them, the switch ports come up, and the interfaces start sending traffic but do not receive any. Additionally, no MAC addresses are detected on these devices, which the customer has confirmed.

My question is: Can a Cisco L2 switch forward traffic between devices that don't have MAC addresses?

[marce1000]

   - They can't ; how do you expect these devices to communicate if they don't have mac addresses ?

 M.

[Leo Laohoo]

Nope.  They won't work with Cisco switches.  Or any other vendor's switches.  

Those old equipment are interconnected using co-axial with non standard protocols.  

They might work with cheap hubs.  

[liviu.gheorghe]

Hello @Ab26 ,

If the interface on the customer device is ethernet, it MUST have a MAC address - it's the way that ethernet is designed.

You should investigate what type of interfaces are on the customer devices - maybe they are serial devices with a RJ45 connector like Cisco has in case of console or AUX ports on older equipment.

Hope this helps.

[Kasun Bandara]

@Ab26 Hi, its not working without MAC address in switches. switches need MAC address to transmit traffic. may be your device is using different kind of protocol. if its industrial protocol, you can use industrial protocol supporting switches. 

[MHM Cisco World]

No Mac and you use ethernet IEEE 802.3?

It must use different protocol like PPP/HPLC or other.

Show interface check protocol it use

MHM

[Richard Burts]

The OP tells us "The system was previously connected via direct cables". I would like to know more about what those devices are and what kind of cables these really were. I am wondering if they might be using the old IBM networking protocols (SDLC etc) or something similar that did not use mac addresses and did not use IP addresses.

But the question here is about connecting devices to modern switches and these switches are dependent on devices having mac addresses. Without mac addresses the devices will not communicate with switch.

[Joseph W. Doherty]

I think it unlikely a Cisco switch will pass the traffic if the devices are using an unknown framing format (implied by lack of using a MAC).  @Leo Laohoo 's suggestion that a hub might work, for at least two hosts, makes sense but then it's possibly not useful as you could still use a dedicated cable.

It might be useful to wire capture what those old hosts are doing.  Perhaps they are just using one of the older/earlier framing formats.  Knowing exactly what they are doing may lead to a remediation method.