Web Hosting Talk : Web Hosting Main Forums : Colocation and Data Centers : Yet another fiber optic question, this time 10G Cisco Optics

[cheezus]

We've got some C3KX-NM-10G modules coming for our 3750x stacks, one stack in each rack, and are looking to uplink them. The racks are side by side.

Each rack has 2 3750x stacked. We figure we'll do 2 uplinks, 1 from each switch in each rack to each other in an etherchannel.

The question is, I see all these different types of 10G optics to go into the module. The module itself has 2 sfp and 2 sfp+ ports.

I see:
SFP-10G-ER
SFP-10G-LR
SFP-10G-LRM
SFP-10G-SR
SFP-10G-ZR

Seeing as the cabinets are side by side the obvious choice appears to be SFP-10G-SR. But is that really the best choice?

EDIT: Also is there a reason to buy new Cisco vs. used Cisco vs. new Third party?

[Spudstr]

10G-SR or 10G-LR is what you can use. you could use LRM but thats kinda the "odd one no one ever uses"

Depending on the MMF you use.. OM4 ranges 400M, OM3 is 300M OM2 is 82m om1 is 33 meters.

LR will do 10km without any problems

SR/LR are LED based optics where the ER/ZR are actual laser based iirc.

Third party optics will be generally 1/3rd the price of cisco optics. There are a slew of quality optics that come out of HK that work great with cisco. Might have to do the hidden service support-unsupported command but they should work fine as long as they are also coded for cisco in the eeproms.

[cheezus]

Cool man, thanks. Looks like SR are more plentiful and cheaper so that seems the best route. Also looks like used cisco is only $40 more than new third party.

Do these things wear out or have any other problems that make buying used not the better move?

[Spudstr]

Originally Posted by cheezus

Cool man, thanks. Looks like SR are more plentiful and cheaper so that seems the best route. Also looks like used cisco is only $40 more than new third party.

Do these things wear out or have any other problems that make buying used not the better move?

Just as long as the temp/humidity is fine these things will outlast you and I.

[spaethco]

Originally Posted by Spudstr

you could use LRM but thats kinda the "odd one no one ever uses"

I agree if that I were just buying an optic or two, I'd go SR just for future interop reasons. The LRM optics are great for interconnecting Cisco gear that support them, but even Cisco doesn't support LRM across all their product lines. In particular, the Nexus 5ks and 2ks have no ASIC support for the LRM SFP+.

All that said, for interconnecting our Nexus 7ks and 6500s we use LRM optics exclusively. When you're ordering a few hundred 10gig optics, the savings of LRM are completely worth it.

[david_halliday]

If you only have a few racks (4) and they are adjacent you can use the 3m stacking cables and connect them via the 64Gig stacking ring. (I believe the stack limit is 9 switches.)

[cheezus]

Originally Posted by david_halliday

If you only have a few racks (4) and they are adjacent you can use the 3m stacking cables and connect them via the 64Gig stacking ring. (I believe the stack limit is 9 switches.)

We thought about this and even found longer stackwise cables than 3m. However we have about 35 lacp groups in one rack and 40 in another. The stack limitation is 64 so it wouldn't work for us.

[david_halliday]

OK if you have to use the SFP+ why not just use 10Gig, direct attach cables?

SFP-H10GB-CU5M= (or 3m or 1m version) save a bunch of money, has lower latency and you need 1/2 as many as it includes both ends.

Also, out of interest what size stackwise cables did you find and where? I am about to do the horizontal stack thing and slightly longer cables would help.


Dave.

[cheezus]

They have 5m, 7m and 10m. I don't have any experience with those lengths though.

http://www.connectzone.com/cab-stack-5m.html
http://www.connectzone.com/cab-stack-7m.html
http://www.connectzone.com/cab-stack-10m.html

What do you mean by direct attach cables?

[Ionity]

How are the cross connects delivered? Probably single mode.

If your not on 10gig now you probably will be one day?

Why hassle with OM2, OM3, etc. single mode will be here for the long haul (no pun intended) for your future expansion. If you go with LR optics for your short runs too you only have one spare part to stock, all of your cables are interchangeable and have a longer shelf life, etc. Just remember to attenuate the LR optics on such a short run.

You can buy a programmer to use the optics in various brand devices as well.

[cheezus]

Single mode, yup. Not 10g to the carriers yet but this time next year it's likely we will be.

[Ionity]

Originally Posted by cheezus

Single mode, yup. Not 10g to the carriers yet but this time next year it's likely we will be.

It was a rhetorical question ;-)

Unless your in a dive joint the carriers will deliver on single mode media...

So you get the point now? Next year you don't have a spare 10gig LR for uplink and 10gig sr for internal.

Just get an attenuator for the short run...or if you use a patch panel the bulkhead will create an air gap and you will be fine.

Some people tie a knot in the cable to reduce the light... Don't do that.

[cheezus]

What is the difference between 50MMF and 62.5MMF in the SR optics?

[david_halliday]

Originally Posted by cheezus

What do you mean by direct attach cables?

Also known as twinaxial or twinax, basically they are 10Gig copper cables/SFP+ that plug into the SFP+ slots and can run over short distances. (typically 5m or less).

http://www.starcompu.com/cisco-sfp-h10gb-cu5m.html

Dave.

[david_halliday]

Originally Posted by cheezus

What is the difference between 50MMF and 62.5MMF in the SR optics?

Its the size of the core. 50 micron vs 62.5 micron. OM3 is narrower. In laymans terms the narrower the core the more direct the light path (and less paths the light can take) this means the narrower the core the more efficient the fiber. Once you get to 9 microns (the size of the core in single mode) there is only one path the light can take making it more efficient so the same amount of photons will travel further. (Its not quite like I describe but it is a very good analogy.)

Personally if the run is to big for twinax copper I use single mode. (Even for short distances) I have relegated anything multi mode to the scrap heap.

To learn all about fiber go to the following link and work your way over the table starting at Jargon:

http://www.lanshack.com/fiber-optic-tutorial.aspx

Dave.