The big difference is that EtherChannel uses a source/destination translation to
decide on which port in the EtherChannel Group to use for each
source/destination pairing in a frame. It doesn't use round-robin or destination
hashing or fragmentation or anything like that.
If you have a 2 port EtherChannel Group an XOR on the last bit in the frames
source and destination MAC's is done to select the channel(port) to transmit the
frame on.
e.g. src mac = xxxxxxx0, dst mac = xxxxxxx1 then channel 1 of the
EtherChannel Group is used.
src mac = xxxxxxxx0, dst mac = xxxxxxx0 then channel 0 of the
EtherChannel Group is used.
For a 4 port EtherChannel Group the last two bits of both the src and dst MAC's
is used to select the channel(port) to transmit on.
e.g. src mac = xxxxxx10, dst mac = xxxxxx00 then channel 2 of the
EtherChannel Group is used.
src mac = xxxxxx10, dst mac = xxxxxx11 then channel 1 of the
EtherChannel Group is used. (Remember XOR not OR)
There are other rules to EtherChannel groups.
All ports must be contiguous and on the same card (Except for the 6000's)
Only 2 port and 4 port EtherChannel Groups can be used, no 3 channel groups or
larger than 4 (Except for 6000's)
All ports either must be on same VLAN or they all must be Trunks.
If they are Trunks they must allow the same VLAN's.
Which brings us to link resiliency.
I know that in a 2 port group when one link fails all traffic simply goes across
the other link as EARL learns the MAC's on each side of the link.
However for a 4 port group it is written that traffic that was supposed to go
across the failed link is "migrated to the neighboring segment". My question is
whixh side is the neighbor? e.g. port 2 fails, does it use port 1 or port 3?
Hope this helps.
Darren
Albert Ip wrote:
> Cristina,
>
> When you have more than one port connect to another switch, spanning tree
> will disable all but one of the port. If that port (live) connection is
> cut, spanning tree will enable one of the other port to transfer data. This
> process waste ports that's disable. When you use Fast EtherChannel, the
> switch will use all the ports to move data. Better use of ports. When you
> set up the EtherChannel, the switch will decide that these MAC address will
> use this port and these MAC address will use that port (I don't know the
> math for this). If one of the port goes down, it will automatically use the
> other port(s) to forward the data. This is the same as using two routers to
> load balance and backup.
>
> Albert
>
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
> Cristina Hoselins
> Sent: Wednesday, May 31, 2000 11:37 AM
> To: [EMAIL PROTECTED]
> Subject: FastEtherChannel!
>
> All,
> Fast Ether Channel is a trunking technology based on grouping together up to
> 4 full duplex 802.3 Fast Ethernets to provide fault-tolerant high-speed
> links between switches, routers, and servers...My questions to you are:
> How does it work? Which channel out of the four(2) channels is the default
> one? Does it look at the MAC address in order to foward packets!!!!!!
>
> Thank you all.
> Cristina
>
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