Nasser N Khwaja wrote:
> 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,
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That number refers to the size of the MAC Address table... basically, how
many nodes can be hooked up to the switch (directly, via cascaded hub,
multilayer switches, etc) and remember what port every station is on. For
best performance, a switch should be able to remember every MAC Address on
it's side of the router, and therefor after recieving a packet from every
station, no longer have to flood all segments to locate a station. This
is optimum use.
If you were to purchase a switch that can hold 1024 MAC Addresses in it's
table, and attach 1100 stations, the switch will function, it will only be
less efficient. For example,
MAC Address #1 isn't used for a long time, and 1024 other stations "talk"
since... SwitchA will remove the entry for Station1, since "it must be
turned off, and this will free room in the table". Suddenly, a packet for
Station1 comes into the switch... it doesn't have an entry in the
MAC Table, so it floods all ports. This flooding causes excess traffic on
all other ports.
Same scenario, but the switch has a 2048 entry MAC Address Table.
Station1's MAC is never removed, because there is still room in the table
after everyone on the network has talked. The same packet comes in for
Station1, the switch looks up the MAC, and sends it out the appropriate
port. The 1099 other stations don't have to process that packet to layer
2 and drop it.
Regards,
Trevor Corness, CCNA+ACRC
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