3750G Question

I am looking at a 500 node network with a 4510R at the MDF. I need to
replace 3 IDF switches, each of which has 10-24 switches uplinked to it.
Right now they are linked to the IDF at 100Mbps, and I am upgrading the
backbone to Gigabit using the 6 GBIC line cards for the 4510, so would like
to extend at least 1Gbps to each access switch. I have 4 strands of fiber at
each IDF which I can use to uplink the new switches at 2Gbps GEtherchannel
tot he 4510. So, it would be: Access switch -> IDF Switch -> MDF. This
network is a campus network, and the cabling design cannot be changed at
this time. I was wondering about using the 3750G-24TS at the IDF's. It has
24 10/100/1000 ports and 4 SFP ports. The access switches are all
2950T-24's. These are 24 port 10/100 switches with copper gigabit uplinks.
My question is, would the 3750G-24TS be good in the IDF? The client will not
buy a more expensive modular switch like the 4506 or similar which I would
prefer for the IDF's. I can't find in the Cisco docs on the 3750 if all 24
of those ports can be trunk links, ie, are they non blocking or not. Can
anyone shed some light here?

 

With a backplane speed of 32 Gbps (IIRC) all of the ports on the 3750 are
"non-blocking" of course if you are aggregating 24 gigabit copper ports
to 2 gigabit uplink ports so there is going to be a bottleneck in the
design. All of the ports can function as trunk ports from what I recall
but I have never installed one in that manner.

The 3750 has a few different limitations including a maximum of 12
etherchannel connections (fine you say there are only 24 ports that is
until you "stack" multiple switches together)

In reguards to this I think I saw a document on Cisco's site concerning
network design indicating a suggested 8 to one ratio between access and
distribution and 4 to one ratio from distribution to core.

Some of the above is from memory and some from experiance. Double check
anything I say before you make any final decisions as I am not an
engineer.

-Jeff C

 

I like the 8 to 1 number, but in a webinar on Gig to the desktop they
claimed 20 to 1, and that there was no noticable problem at 40 to 1.
I'm not sure I beleive it. I prefer to design with the 8 to 1.