hi all
My RB450G ETH5 (PORT5) unexplained failure, does not work.
Determine the hardware problem.
now I try to resolve it,some problems need help
thanks!
Check termination resistance between Tx and Rx lines, it is to check the definition of RJ-45,between 1 and 3,or between 2 and 6???
can someone help me 
How far I remember this test not work for Gbit RB . If you got lightening or static electricity just replace AR8316 swich chip.
No lightning or static electricity, unexplained.
So step by step test, and then try to exclude it.
If the switch chip, is very troublesome for me, because here it is difficult to buy it. 
If you have warranty send RB by warranty to your distributor.
Unfortunately you need a new board, unless you can get the chip and have access to SMD re-working tools.
Even if you replace the chip, you might find it something else.
Your best hope is to replace the ethernet socket, because i think it is thru-hole mounted (so easier to replace) and it has baluns and resistors in it which may have been zapped by something.
You might also find exactly the same socket on some other device that you have, so maybe an easier way to find a spare.
If that doesn’t work, you may as well give up, as your Time is also worth money. Better to buy a new board, and use your time working for money, rather than trying to save just the money.
Yes, if only the ethernet socket, I will try to replace, if it is the fault further. Then I will give up, because it is too complicated for me