>What does it mean to say that the Catalyst 1912 has 1024 MAC Addresses,
>while the Catalyst 2828 has 8192 MAC Addresses.
>Can anyone please explain?
>Thanks in advance.
>Reply to,
>[EMAIL PROTECTED]
>
You touch on what is an interesting problem in product design, which
shows why products differentiate.
Specifically, this refers to the size of the MAC address lookup table
on the bridge. It doesn't mean that there can only be 1024 or 8192
MAC addresses defined, only that many that the switch will handle
quickly by knowing immediately whether to block or forward the frame.
Cisco and Bay(Nortel) have taken different approaches to MAC tables.
Neither one is best under all circumstances. Cisco defines a table
for the entire switch, which is used by all broadcast domains.
Nortel defines a separate 1K table to each port.
Let's say you are brought in to fix a horribly performing campus
network that has 1000 active hosts in a broadcast domain. Fits easily
into 1K. In a calm, rational way, you split that single domain into
four subnets. 250 each. No problem.
But each subnet then goes through 20% growth, giving 300 hosts per
domain. Weird and unpredictable performance starts occurring, as the
four subnets compete for slots in the cache. In this case, if you
know the subnets will individually have no more than 1K MAC
addresses, the guaranteed 1K of the Bay switch is much more
predictable. Do you have a sane, managed policy about growth? To
coin a phrase, It Depends.
Return to the problem of a horribly performing campus network, but
assume this time that it has 4000 hosts -- quite possible with FDDI.
Connect a Bay switch to this, and it will be in immediate trouble. So
will a Cat 1912. But a 2828 will handle the total number of hosts in
a reasonably predictable manner.
"What Problem are you trying to solve?"
***send Cisco questions to the list, so all can benefit -- not
directly to me***
Howard C. Berkowitz [EMAIL PROTECTED]
Technical Director, CertificationZone.com
Senior Product Manager, Carrier Packet Solutions, NortelNetworks (for ID only)
but Cisco stockholder!
"retired" Certified Cisco Systems Instructor (CID) #93005
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