Re: CRTLINETH RSRCNAME(*AGG)

[DrFranken <midrange@xxxxxxxxxxxx>]

Yeah, in the i world it's almost always about redundancy.  I agree with 
the statements in this thread about Ethernet line utilizations 
approaching zero, especially in the GbE space.

The magic is *VIRTUAL IP. The concept is that at the Ethernet level 
communications isn't about IP it's about the MAC address of the Ethernet 
line. Each of your physical lines (1, 2, 3, more?) has a unique MAC 
address. Each of them also gets a fixed IP that is otherwise not used( 
for example 10.1.1.1, 10.1.1.2, 10.1.1.3. etc) . The IP address assigned 
to the *VIRTUALIP has no home initially, assume it's 10.1.1.100. When 
someone out there says 'Who the heck is 10.1.1.100?'  (An ARP request) 
IBM i picks one of the boys form 10.1.1.1, 2, and 3 to 'proxy' for the 
10.1.1.100 address (say 10.1.1.1). It then sends out it's MAC address in 
the response. All connections at that point forward to 10.1.1.100 go to 
the same MAC address as 10.1.1.1 and IBM i handles the inbound packets.

This is awesome until  the Ethernet line for 10.1.1.1 gets pulled out. 
Now normally nobody would know what to do to find 10.1.1.100 as they 
would continue sending packets to the MAC address of 10.1.1.1 but it's 
down. Until their ARP cache ages out they would be stuck. However IBM i 
says, 'Hmmm, 10.1.1.1 just went boom, and I've hung 10.1.1.100 there. I 
better pick a new home' So perhaps it picks 10.1.1.2 and then sends out 
a 'gratuitous ARP' (that is, one nobody asked for) that says, 
'10.1.1.100 is at MAC Address(of 10.1.1.2)'

All the machines in the network that have an entry for 10.1.1.100 update 
it and immediately begin using the updated entry.

All of this happens so fast that nobody even notices, connections remain 
up, even 5250 sessions continue without delay.

Hope that helps!!

        - Larry "DrFranken" Bolhuis

On 8/2/2011 1:50 PM, rob@xxxxxxxxx wrote:
> I think he is talking about binding 1 IP to multiple NIC's.  The purpose
> being twofold:
> - Redundancy
> - Load balancing
>
> Well, it would be a rare day when I would come close to tickling the
> capability of a 1GB card.  According to what I use the only card that ever
> sees a significant load is a 100MB card on one lpar.  All the rest are GB.
>
> Not sure about the redundancy.  How would one get redundancy?  Ok, I can
> see the card, and/or the cable from the card to the switch.  However I
> can't see multiple switches and stuff.  How could one IP address be on
> multiple switches?  This new huge switch you could have ports on a couple
> of different cards and perhaps they are hot swappable (a coworkers job).
>
>
> Rob Berendt