[c-nsp] 802.3ad questions..

[Per Carlson]

Hi.

> We have (2) Metro Ethernet connections from two different carriers
> connecting our two locations at the moment.  We need to provide for
> redundancy at the L2 level for these, and would like to combine the
> bandwidth into one logical bundle.
>
> We will be using Cisco switches on both sides of the link(s), and it seems
> 802.3ad is the way to go -- but I'm not sure if LACP or EtherChannel is
> appropriate here, or if there is something else I should be considering.

EtherChannel can be used if, and only if, both carriers tunnels the
EtherChannel protocol. Such tunneling is only supported on VPWS (aka
Q-in-Q) type of circuits. For some additional info, for example look
at: http://www.cisco.com/en/US/docs/switches/metro/me3400e/software/release/12.2_52_se/configuration/guide/swtunnel.html#wp1005050

>  Also, to throw another issue into the mix -- these two links are not
> currently equally sized -- one is shaped to 600M, the other is a full Gig,
> so a way to specify link speed and have it load balanced appropriately would
> be great as well.

This can't be fixed with EtherChannels. If you instead use IP, GLBP
(http://www.cisco.com/en/US/docs/ios/ipapp/configuration/guide/ipapp_glbp_ps10591_TSD_Products_Configuration_Guide_Chapter.html)
might solve that (provided you have a decent src/dst distribution).

The old truth "Good, fast, cheap -- pick two, you can't get all three"
still holds, and with L2-switching you are stuck with "fast" and
"cheap"...

-- 
Pelle