OK.
I must be brain dead, today.
(and, yes, Chuck, I *have* had my morning dose of Diet Coke :)
and, yes, I know, "What's so special about 'today' "?
)
As far I can understand it so far, about the only benefit that I see
from VLANs is reducing the size of broadcast domains.
Suppose that I have a switch in the closet with one big flat address
space (well, it couldn't be that big with only one switch, now, could
it ?>). Then someone says,
"You know, we're getting a lot of blah-blah broadcast traffic.
Let's VLAN.
"
OK, fine. We VLAN and put whatever services in each VLAN that are
required to handle the broadcasts (e.g., DHCP service). So, now the
switch doesn't send broadcasts outside a particular VLAN.
But, what's so magic about a VLAN that the switch also decides not to
send unicasts outside a VLAN. Before the VLANs, the switch maintained
a MAC table and knew which port to go out to get to any unicast address
in the entire space. So, why can't it continue to do that after we
arbitrarily implement some constraint on broadcast addresses?
It seems to me that the same, exact MAC table, with an additional VLAN
field would not require that restriction. If it's a broadcast, send the
packet only out ports with a VLAN-id that matches the source port's
VLAN-id. If it's a unicast, handle it just like we used to.
Similarly, even if we have 5 switches, I just don't see the requirement
that we (as switch-code designers) must block unicasts and resort to a
routing requirement.
Even with 500 switches ... well, let's not get ridiculous :)
I feel that there is a simple point that I've overlooked, so I will
continue to RTFM while I await your responses.>)
-------------------------------------------------
Tks | <mailto:[EMAIL PROTECTED]>
BV | <mailto:[EMAIL PROTECTED]>
Sr. Technical Consultant, SBM, A Gates/Arrow Co.
Vox 770-623-3430 11455 Lakefield Dr.
Fax 770-623-3429 Duluth, GA 30097-1511
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