Trunk or etherchannel

[Andy White]

Hi,

I have installed a 2960G switch and trunked it to a 3750's gig SFP port (the last available).  I have 2 x 3750 FE swithes in a stack and I want to give this 2960G soem redundnacy.  Would you:

1. keep the gig trunk and add a second trunk into the other switch inthe stack which will have to be a 100mb trunk as I have not spare sfp gig ports left onthe 3750 stack?  Then should it go down the 100mb trunk will start after 50 sec due to STP?
2. Create an etherchannel include the 1gb port Port cost 4) and 100mb port (port cost 19), the port cost will reduced.
3. Free up the 1gb port and use 2 100mb ports in an ether channel, 1 in each 3750 switch in the stack from the 2960g?

I see the bandwidth is around 150mb on the trunk.

Thanks

[smehrnia]

Hi andy,

1) you could implement this option and use Rapid STP (802.1w) for very much faster convergence, rather than waiting for 50 sec.

2) you can not create an etherchannel between non similar ports. either all should be 100mbps or 1gb.

3) if you dont have another application for the Gig interface, i think option # 1 is better, since here you'll get 200Mbps tops, and there under normal condition you'll have 1 Gbps bandwidth available.

plz rate helpful posts,

Soroush.

[Andy White]

Hi,

What is the difference between rapid stp and the default?

[smehrnia]

There are some Technical enhancements and differencies in the way they do the job which you can find in below link:

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_white_paper09186a0080094cfa.shtml

but what's important here is the faster convergence time that Rapid Spanning Tree (802.1w) provides comparing to common spanning tree 802.1D.

Hope it Helps,

Soroush.