Unexplained Traffic on Tx

RouterOS General
1

Hi All, I am not new to MT at this point and have installed approximately 90 of the MT devices replacing Cisco Catalyst legacy devices. Biggest challenge is PVST vs RSTP. As you can imagine they don’t really like each other.

My latest challenge is I just finished removing the last 2 Cisco devices from a customer network and everything seems ok at this time.

My question is this.

I am using bridge mode on all the devices. What I see is that what I am receiving on a specific port for bandwidth seems to be transmitting on all interfaces that are associated with the common vlan.

I have not seen this issue before on any of my migrations and all of my migrations are pretty much standard at this time with a few 1 offs but this is not one of them.

Can anyone explain why receive traffic is being sent out every port with a common vlan?

Thanks in advance.

I have attached a screen shot and you will see what is being received on sfp6 is being sent out sfp1,sfp3, and sfp12.

I would not expect to see that.
TX vs RX.pdf (316 KB)

2

This is a normal behaviour of a switch/bridge for three categories of traffic:

  • traffic to broadcast MAC address (ff:ff:ff:ff:ff:ff)
  • traffic to multicast MAC addresses (any address with the LSB of the first byte set to 1) - on switches that support IGMP or similar, this may depend on subscriptions to the multicast groups
  • traffic to unicast MAC addresses from which no frame has arrived to the switch yet - this behaviour is necessary to allow opening communication to newly connected devices

So a source of one of these three types of traffic is connected to sfp6, and to find out whether the amount of that traffic can be reduced or not, you have to analyze the traffic - connect a PC to a free port and make that port a member of the same bridge and VLAN like sfp1, sfp3, and sfp12.