Skip site navigation (1)Skip section navigation (2)
Date:      Mon, 20 Nov 2000 17:20:00 +1300
From:      David Preece <davep@afterswish.com>
To:        freebsd-questions@freebsd.org
Subject:   802.1q, bonding and mpath
Message-ID:  <5.0.0.25.1.20001120163545.00a0cd90@pop3.i4free.co.nz>

next in thread | raw e-mail | index | archive | help
I just spent the afternoon trying to work out if channel bonding / 
etherchannel / trunking is possible on FreeBSD. The answers from the 
mailing list archives say either:

1, Nope.
2, Yup, but it's messy and you have to use PPPoE.
3, Yup, use a kernel hack called mpath.

Note that (possibly due to a bad ISP) flirble.org, where mpath should be, 
appears to be currently unavailable so I'm slightly clue disabled at the 
moment.

None of this seems to answer what, for me, appears to be the basic 
question: When a client machine ARP's for the servers IP, it has to reply 
with a link layer (i.e. ethernet MAC) address. All packets from client to 
server (or nearest router to server) then travel between these two MAC 
addresses. How does this work with two network cards then? Either:

a, Both network cards have the same MAC address, but then how does the 
switch know which card to send an incoming packet to? This appears to be 
the approach taken by mpath since "the ARP request is replied by the head 
of the cluster" (pseudo quote, sorry). Is this something the switch has to 
understand?

b, The cards have different addresses and the ARP reply is cooked such that 
it comes from one or the other card - like round robin DNS, only for layer 
2. This is all well and good, but the next hop router would have an ARP 
cache, so presumably all connections would go to one card or the next.

c, None of the above.

I also don't get the connection with 802.1q VLAN's. 802.1q appears to be 
about marking ethernet packets with a VLAN number such that your one LAN 
can be considered to be many LAN's electrically isolated. Great, I've even 
used it on a cisco switch and it worked a treat. I cannot find it's 
connection with the trunking/bonding problem though...

Dave



To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-questions" in the body of the message




Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?5.0.0.25.1.20001120163545.00a0cd90>