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Re: Is agr broken?



I've been doing a lot of LACP work recently as part of my day job so I've spend a lot of time debugging code (based on the FreeBSD LACP code which originally came from NetBSD) and reading the LACP standards so hopefully I'm qualified to answer questions about LACP. ;)


On 12/01/2017 13:05, Robert Elz wrote:
Try
	ifconfig tap0 media 100base-TX

(and similar for other tap interfaces you use) after the interface is
created, before adding it to the agr interface.

You can use whatever speed you like (though it has to be one of the
standard ethernet rates - tap is pretending to be an ethernet after all)

It probably helps but as far as I can tell from looking at the 7.x lacp code as log as the media subtypes are the same the netbsd LACP code will treat them as equivalent speeds.

I suspect that the agr driver will bias data being queued to its component
interfaces based upon their relative speeds (which is why it needs to know
what they are), so if you want tap0 to get more packets than tap1 make
it pretend to be faster...    Otherwise set them all the same, and it should
make no difference what value is picked.

Actually if agr is configured for LACP then there are 2 requirements:

1. interfaces in the aggregate must report as full duplex.
2. For interfaces to actually be combined they must all be operating at the same speed. These are both requirements of the LACP protocol standard.

In LACP the frame distribution is determined by a hash algorithm not link capacity.


Mike



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