From: asadovnikov (asadovnikov@comcast.net)
Date: Tue Nov 04 2003 - 02:13:32 GMT-3
Agree.
But first time the fiber or GBIC goes bad on say 4 link GigEtherChannel, not
down, just bad enough to loose packets, and some packets get lost and other
do not within the bundle, and you get to find it...
This coin does have another side.
Best regards,
Alexei
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Mike
Williams
Sent: Monday, November 03, 2003 11:31 AM
To: 'Carter, Lee'; 'Howard C. Berkowitz'; ccielab@groupstudy.com
Subject: RE: Dumb Question but will ask
Good point........ Stability is good =)
Mike W.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Carter, Lee
Sent: Monday, November 03, 2003 8:32 AM
To: 'Mike Williams'; 'Howard C. Berkowitz'; ccielab@groupstudy.com
Subject: RE: Dumb Question but will ask
Layer 3 etherchannels are better than just merely load balancing over
multiple layer 3 links. Think of if like this:
Etherchannel bundles links together as to look as though they are one. This
is good for a layer3 or layer2 solution because in layer 2 if one of the
links is dropped there is no SPAN on the network. In a layer 3 environment
if one of the two links is to drop you do not loose any layer 3 routing
protocol adjancies!!! this is good because there is no Layer 3 route
changes. This can be a very good think especially if you have a bad link
that is bouncing. Your layer 3 domain will stay stable. Just like as in the
layer 2 domain there are no SPAN's in the layer 3 domain there are no route
changes.
HTH.
-----Original Message-----
From: Mike Williams [mailto:ccie2be@swbell.net]
Sent: Sunday, November 02, 2003 6:22 PM
To: 'Howard C. Berkowitz'; ccielab@groupstudy.com
Subject: RE: Dumb Question but will ask
Howard,
Actually, Cisco does distiguish between L2 and L3 etherchannels:
http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/ios127xe/con
fig/channel.htm
Having said that, it boils down to this: A L3 Etherchannel has an IP
address configured on it's port-channel interface. So basically, aside from
the engineering putting an IP address on it and "treating" it as L3, it's
the exact same thing as a L2 etherchannel...... So I don't think it's
"marketingspeak" as much as simply using a term to describe the "mode" of
use of a given etherchannel bundle.
You bring up a good point not to confuse this with the IOS functionality
that will load balance over routes it considers equal (whether learned
dynamically or from static routes, etc). However, the load-balancing we're
speaking of (as I'm sure you well know) is specific to an etherchannel
bundle, and can be based on A) dest. MAC, B) source AND dest MAC, C) dest
IP, or D) source AND dest IP (note* when I say "AND" here, it's really an
XOR operation performed on the source and dest MAC/IP addresses to determine
which link in an etherchannel bundle is taken). So it's clear that
etherchannels (whether being used as a pure L2 link or as an L3 link) can
use Layer 3 information to determine which link traffic goes on, but this is
separate from the IOS load-balancing you speak of, correct?
I see your point, tho, that using terms like L2 and L3 etherchannel could
confuse. I gave an example where we have a etherchannel link between a 7500
and 6500 where the 7500 side has an IP (and would be called an L3
etherchannel) and the 6500 side doesn't (and would be called an L2
etherchannel). This shows that you don't even have to have both ends of an
etherchanel configured the same (as far as being L2 or L3).
Mike W.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Howard C. Berkowitz
Sent: Sunday, November 02, 2003 8:36 AM
To: ccielab@groupstudy.com
Subject: RE: Dumb Question but will ask
I'm confused. Has Cisco, somewhere, actually defined L3 EtherChannel?
If it has, it's yet another case of marketingspeak, creating
meaningless concepts such as L3 vs. L2 switches.
If it hasn't, and we are speaking of load distribution based on L3
information, we are speaking of a normal IOS function. Let me repeat:
load sharing has nothing to do with the routing protocol. You can
load share among static routes.
At 8:26 AM -0600 11/2/03, Mike Williams wrote:
>If I'm not mistaken, you can use the source IP and dest IP addresses to
>determine which link in a L2 etherchannel that traffic will take. So
>even if you have a L2 etherchanenl between 2 routers, the traffic can
>balance over the links (in proportion to the distribution of the
>source/dest addresses).
>
>Mike W.
>
>-----Original Message-----
>From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
>Ryan Cheng
>Sent: Sunday, November 02, 2003 1:25 AM
>To: Shafi, Shahid; ccielab@groupstudy.com
>Subject: Re: Dumb Question but will ask
>
>
>Hi Shahid,
>
>Etherchannel is to make 2 or many physical links to be a logical link,
>but the question comes, how to load-share the traffic into each link?
>
>L2 Ethernet: it makes use of the L2 information (e.g. Ethernet DA and
>SA) as a matching criteria, says any traffic which has a different DA
>and SA in the ethernet header will be flowed into different physical
>link
>
>L3 Ethernet: in contrast, the L3 information (e.g. destination and
>source IP
>address) is used in this case
>
>If you are using a L2 ethernet channel between Routers, the
>load-sharing won't work since all traffic between the routers have a
>fixed Ethernet DA and SA.
>
>Hope my reply is useful.
>
>Regards,
>Ryan
>
>----- Original Message -----
>From: "Shafi, Shahid" <sshafi@qualcomm.com>
>To: <ccielab@groupstudy.com>
>Sent: Sunday, November 02, 2003 8:40 AM
>Subject: Dumb Question but will ask
>
>
>> Hi Guys,
>>
>> A stupid one but I'll ask though I think I know the answer: What is
>> the difference between layer2 and layer 3 etherchannel? What wont
>> work
>
>> if I use Layer 3 Etherchannel between switches? VTP?? What is more
>> efficient and why?
>>
>> Any input is great!
>>
>> thanks
>>
>> Shahid
>>
>>
>>
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