Re: Ethernet Bridging

[Jim Oberholtzer <midrangel@xxxxxxxxxxxxxxxxx>]

My own take on proxy ARP is refer to Drs. 1st, 3rd, 5th, and 7th comments.

I know good network folks that can't really figure it out.

It's really number 6 that counts.  When it works, it works great, but 
troubleshooting it is a miserable task when things go wrong.

Jim Oberholtzer
Chief Technical Architect
Agile Technology Architects


On 8/20/2013 1:27 PM, DrFranken wrote:
> I would not recommend proxy ARP.
>
> 1) Most i Admins are confused by Proxy ARP.
> 2) It works at the O/S Level so it's going to use more overhead.
> 3) Most i Admins are confused by Proxy ARP.
> 4) You need to understand subnetting to make it work.
> 5) Most i Admins are confused by Proxy ARP.
> 6) It's not a very standard thing and will be hard to troubleshoot
> especially compared to Bridging.
> 7) Most i Admins are confused by Proxy ARP.
>
>           - Larry "DrFranken" Bolhuis
>
> www.frankeni.com
> www.iDevCloud.com
> www.iInTheCloud.com
>
> On 8/20/2013 2:23 PM, Evan Harris wrote:
>
> > >  If the guest partition and the host partition are on the same network
> > >  (which they must be if you want to assign an address to the adapter) then
> > >  you might be better using proxy ARP to assign an address to the guest.
> > >  https://publib.boulder.ibm.com/iseries/v5r2/ic2924/index.htm?info/rzalm/rzalmtcpip.htm
> > >
> > >  Personally I have found the Ethernet Bridging a really useful solution. The
> > >  chief advantage is it allows me to use one PORT per multiport NIC for a
> > >  partition (or partitions) rather than having to assign an entire card.
> > >
> > >  I found the HEA a bit clunky but only used t a couple of times.
> > >
> > >
> > >  On Wed, Aug 21, 2013 at 5:10 AM, Mitchell, Dana<dmitche@xxxxxxxxxx>  wrote:
> > >
> > > >>  Has anyone worked much with 'Ethernet Bridging Between IBM i Host and IBM
> > > >>  i Guest'?   We are working on adding a 2nd LPAR to a production machine and
> > > >>  I thought it would be a good idea to just one an Ethernet port on the first
> > > >>  machine and bridge traffic from it to the new LPAR.  After doing some
> > > >>  research on the subject, I found this document:
> > > >>  http://www-01.ibm.com/support/docview.wss?uid=nas8N1011193   it explains
> > > >>  what needs to be done very well but comes with one caveat:
> > > >>
> > > >>  Important Note: IBM suggests that the selected Ethernet resources be used
> > > >>  for only layer-2 bridging and not for IBM i TCP/IP configuration. There is
> > > >>  a significant increase in processor usage for any host traffic that uses
> > > >>  bridged resources. In addition, any line description that is used for
> > > >>  bridging receives many frames that are not useful to the TCP/IP stack.
> > > >>  These frames use unnecessary processing resources. The virtual Ethernet
> > > >>  line on the host does not require an interface. You only need the physical
> > > >>  and virtual lines active for the bridge function to work. You should not
> > > >>  have an interface on the physical line used for the bridge either. Create a
> > > >>  separate physical line&  interface for network traffic on the Host.
> > > >>
> > > >>  If I'm reading this correctly it seems IBM is implying that the bridging
> > > >>  function is too much overhead to both service the host partition with IP
> > > >>  traffic and bridge traffic from LPAR#2 also.   So by my math that makes
> > > >>  this facility pretty useless until you get to 3 or more LPARs.   Is anyone
> > > >>  doing this now, and can verify that is it or is not too much overhead?
> > > >>  Why oh why did they discontinue HEA?
> > > >>
> > > >>  Dana