NO-OP Ethernet Packet - Kind of Keep-Alive

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I'm looking for some type of Ethernet packet that does nothing! Some type of "No Operation" just to keep alive.

I know that this is not exactly the right place to ask about it, considering that is not directly related to Wireshark. But I believe the somebody I'm here cold help-me.

I said It could be "Ethernet", but could be "IP" also.

I' trying o solve some issues with flood caused by mac aging time.

I tried to use ARP-Request packets, or Broadcast destined Pings. But those dind't serve as we desired... On big environments(several routers) it became too costly in CPU.