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Forum: FPGA, VHDL & Verilog how to fix collision reset problem in ethernet mac table


how to fix collision reset problem in ethernet mac table
von Melik S. (Company: Kocaeli Universty) (melik)

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In a project I'm working on an FPGA, I'm converting a 48-bit MAC address 
to 16-bit using the Hash algorithm. RAM size is 2^16 bits and I have 8 
ETHERNET ports. I am using the resulting hash as ramin address port. 
Each ethernet port has multiple source addresses. The questions start 
here.
1) example: A packet with source address A was received from ethernet 
port 8. After passing the 48-bit A source mac address through the hash 
algorithm, the 16-bit X ram address is formed. When going to the B ram 
address, the 1st port information -> "10000000" is written.
 A packet with source address B arrived from Ethernet port 1. After 
passing the 48-bit B source mac address through the hash algorithm, the 
16-bit X ram address is formed. Going to B ram address, 1st port 
information -> "10000001" is written.
Currently, if a destination MAC address with the same X ram hash address 
comes in, it will be forwarded to both port 8 and port 1.
Is this operation correct or how can it be done with another operation?

2) Since there is no RAM reset process in FPGA, how can I periodically 
delete the MAC Table addresses I wrote to the RAM?

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Re: how to fix collision reset problem in ethernet mac table
von Duke Scarring (Guest)

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Melik S. wrote:
> 2) Since there is no RAM reset process in FPGA, how can I periodically
> delete the MAC Table addresses I wrote to the RAM?
I would use a finite state machine (FSM) or that.

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