Fiber cable for trunking in gigabit ether ports

itdaddy · July 2008

Hey ccnp gurus, I had this question from someone who was trying to connect
a Gig Ethernet port using fiber cable is this even possible? And doesn't fiber have a higher speed? than Gigabit speed? I have seen Gigabit Ethernet cable for trunks sure but to instert a fiber cable into a Gigabit port is that possible even if it is a Gig Ether port? I am still learning
who knows it might be possible. But why would you put fiber in a Gigabit ether port, arent youonly going to get a gigabits worth of speed. Isnt it kind of a waste?? thanks a head of time.

And also, does anyone have a good config referrence to config and hook up this kind of conifgureation..thank you!

tech-airman · July 2008

itdaddy wrote:

Hey ccnp gurus, I had this question from someone who was trying to connect
a Gig Ethernet port using fiber cable is this even possible? And doesn't fiber have a higher speed? than Gigabit speed? I have seen Gigabit Ethernet cable for trunks sure but to instert a fiber cable into a Gigabit port is that possible even if it is a Gig Ether port? I am still learning
who knows it might be possible. But why would you put fiber in a Gigabit ether port, arent youonly going to get a gigabits worth of speed. Isnt it kind of a waste?? thanks a head of time.

And also, does anyone have a good config referrence to config and hook up this kind of conifgureation..thank you!

itdaddy,

Do the fiber cables have an ST or SC connector on them?

srg · July 2008

itdaddy wrote:

Hey ccnp gurus, I had this question from someone who was trying to connect
a Gig Ethernet port using fiber cable is this even possible? And doesn't fiber have a higher speed? than Gigabit speed? I have seen Gigabit Ethernet cable for trunks sure but to instert a fiber cable into a Gigabit port is that possible even if it is a Gig Ether port? I am still learning
who knows it might be possible. But why would you put fiber in a Gigabit ether port, arent youonly going to get a gigabits worth of speed. Isnt it kind of a waste?? thanks a head of time.

And also, does anyone have a good config referrence to config and hook up this kind of conifgureation..thank you!

Ofcourse you can use fiber in a gigabit port, there are even fastethernet (100mbit) fiber sfp's with lc connections ( i believe the cisco 3400ME has those )

itdaddy · July 2008

tech-airman

thanks...this guy asked me and I wasnt sure. Okay so the ends can be so that it will
jive with the port and then do you have to config it in such a way that it knows it is a
fiber cable so it will work. This guy has 2960 switch(fiber capable gig ports) linked to
a core switch. I really dont know his connections. I am assuminghe has the the right connections. Do you know of a config where I can get to config this gigabit trunk/uplink
port with fiber cable. I guess I do not understand if fiber is way faster than Gigabit isnt it?
What a waste of a cable. I guess also what I am asking you guys is isnt fiber unlimited in speed
or the speed of light? vs gigabit cable 1000 MBbps??? isnt a waste or can you guys enlighten
me.thanks a lot for helping. And if you know of a config I can look at for trunking with Gigabit
fiber uplinks that would be great. I just need the configs. I forget the other switch but he is using
those new 2960 switches and then link to a Core switch that is much bigger with Gigabit uplinks/trunks..

thanks to both of you for your replies I really do appreciate your knowledge and hope someday I can help someone as well!

ixg123 · July 2008

Hi itdaddy, seriously ... forget about the physical medium!

Yes, optical fibre can carry data at higher rates than regular twisted pair. However, there is much more too it than that. Optical fibre can be used to carry data - even at low speed - further than copper can. Fibre is also not impacted by electrical noise (for example the sound that you here from your speakers when your cellphone is just about to start ringing) and so can be used simply for this reason. Just "for interest", not all fibre is created equally ... and neither are the light sources (lasers or LEDs) that put the data onto the fibre in the first place! Some solutions (eg Multimode) only work for short distances at fairly slow data rates (1GBit/s being pretty close to the max). Single mode fibre with a high quality source can reach sites 30+ miles away for 10Gbit/s Ethernet ... something that you couldn't even dream of with copper.

As for transmission at the speed of light, that would simply be the delay between turning the light on at one end, and "seeing" the light at the other. The transmission rate (the 1Gbit/s data rate) describes only how fast that light needs to be switched on and off ... for the distances that you are looking at you really wouldn't be able to measure the "advantage" that propogation (bits moving along the cable) at the speed of light brings.

Finally, for configuration, just treat is as any other trunk port. It has a different name and auto-negotiation for rate/duplex works, but the theory and commands are exactly the same for GigE as you covered for 10-baseTx in the CCNA prep.

Paul Boz · July 2008

Ethernet isn't the cable. It's the technology that runs over the media. You can run ethernet over fiber optic media just like you can run ATM or other encapsulation protocols.

Kaminsky · July 2008

itdaddy wrote:

.... I have seen Gigabit Ethernet cable for trunks sure but to instert a fiber cable into a Gigabit port is that possible even if it is a Gig Ether port? I am still learning .....

Physically you'd need the fibre module to plug into (your post wasn't clear and I had initial images of you trying to blue tak the end of a fibre into a rj-45 ethernet slot - appologies) but the end to end link will still flow at the slowest link in the chain. Say the demark given by your supplier for your site comes in on fiber as opposed to a copper pair (and you paid through the nose for the link inside the box in the road to get the proper link to the exchange - you have to watch them ... they can be really sneaky). From that demark point you then connect it to a device that has thin net at 100mb to a switch that then goes fiber again to a different part of the site, the thin net in the chain WILL be a bottleneck (I've tried explaining this to some of our designer PMs and it's right over their heads). Yes the fibre can go at star trek speed but in that chain you have a slow link which, if you think about it as road works for a car, will control the whole time of the journey. With the water analogy, a lot of wide pipes soldered together and a thin pipe in the chain, is going to produce a trickle from the fat pipe at the end of the chain regardless of the force of water coming in at the other end. You have to think about improvement of the whole chain.

Great if your friend is willing to stump up for the fibre in but you have to think of the overall flow. Paying a lot of money to stick in a fibre stretch might look great on paper but if you have a lot of 10mb or 100mb links, that's still pretty much the speed youre gonna get.

Money wasted for not a lot of improvement.

Hope this applies to what you were initially on about.

Kam.

itdaddy · July 2008

Kaminsky

thanks; that is what I thought; if it isnt all Fibre then to me it is a waste unless there is a be warrant for the speed at Star Trek Speed I like that phrase you used! haha
thanks

Yeah, I wasnt clear cause I wasnt sure at all myself; thanks and it showed hee he
but cool stuff thanks for your help!

Fiber cable for trunking in gigabit ether ports

Comments