Is fiber cable still an expensive solution? Samuel Goldwyn - "I'm willing to admit that I may not always be right, but I am never wrong." - http://www.brainyquote.com/quotes/authors/s/samuel_goldwyn.html
On Fri, Nov 27, 2009 at 8:32 AM, fooler mail <[email protected]> wrote: > On Thu, Nov 26, 2009 at 4:20 PM, plug bert <[email protected]> wrote: >> Hi peeps, >> >> Can one use a layer 2 switch to extend ethernet over 100 feet? >> >> Ganito kasi: we are planning to get a new office unit, and from the looks >> of it the cabling will >> definitely be more than 100 feet. We plan to install around 10 cables in all. >> >> >> Can we just break up each cable, each representing a different subnet, >> then use a multiport >> switch, set up a layer 2 VLAN with two ports for each subnet, then connect >> the two >> segments to those ports? > > hi, > > you are talking two different things here - ethernet cable length > (layer 1 or physical layer) and vlan (layer 2 or data-link layer)... > > for layer 1... the length of your ethernet depends on the IEEE 802.3 > specification that you are going to use... > > below are some examples of IEEE 802.3 specifications: > > IEEE 802.3 (10base5) - 10 mbps baseband 500 meters coax cable length > IEEE 802.3a (10base2) - 10 mbps baseband 185 meters coax cable length > IEEE 802.3i (10baseT) - 10 mbps baseband 100 meters UTP cable length > IEEE 802.3u > (100baseTX) - 100 mbps baseband 100 meters UTP cable length > (100baseSX) - 100 mbps baseband 300 meters multimode opticla fiber > cable length > (100baseFX) - 100 mbps baseband 2 kilometers multimode optical > fiber cable length > IEEE 802.3ab (1000baseT) - 1000 mbps baseband 100 meters UTP cable length > > take note that the metric used here are meters and not feet as what > you mentioned above... > > since you didnt mention what kind of switch you have... ill discuss it > here so that you can design what is best for your setup... > > there are two kinds of hub: > > 1. passive hub > 2. active hub > > assuming you just want to connect two PCs directly without the hub... > diagram below show you the distance: > > for 100baseTX (100 meters): > > PC <---------- 100 meters max ----------> PC > > you need crossover cable for that... > > for passive hub: > > PC <------- distance A -------> passive hub <------- distance B -------> PC > <------- > distance C --------> PC > > distance A + B is less than or equal to 100 meters > distance A + C is less than or equal to 100 meters > distance B + C is less than or equal to 100 meters > > for active hub... this is called now a switch... an active hub or > switch has a repeater in it (unlike with passive hub which dont > have)... repeater belongs to layer 1 or physical layer... > > function of a repeater is to extend network length... repeater receive > and decode data from a worst case noise, timing and signal amplitude > conditions.. it retransmits the data with the correct timing and > amplitude as well as transmitting a jam signal throughout the network > if a collision occurs... > > there are two classes of repeater/switch... class 1 and class 2.. > > class 1 switch can connect two different signaling (eg. 100baseTX and > 100baseSX)... > > the diagram below show the distance depends on the 802.3 specification > that you use: > > PC A <------- distance A ------> class1 switch <------- distance B -------> > PC B > > if PC A and B used 100baseTX (100 meters): > > distance A + B is less than or equal to 200 meters but distance A > and B must not more than 100 meters > > if PC A used 100baseTX (100 meters) and PC B used 1000baseSX (300 meters): > > distance A is less than or equal to 100 meters > distance B is less than or equal to 300 meters > distance A + B is less than or equal to 400 meters but distance A > must not more than 100 meters and distance B must not more than 300 > meters > > class 2 switch cannot connect two different signaling but can connect > to another class 2 switch for additional ports... > > the diagram below show the cable length if you are using 100baseTX (100 > meters): > > PC <-- distance A --> class 2 switch <-- distance C --> class 2 switch > <-- distance B --> PC > > distance A and B must not more than 100 meters > distance C must not more than 5 meters > > class 1 switch cannot connect to another class 1 switch... only one > class 1 switch and two class 2 switches in a given collision > domain.... > > take note.. in a given collision domain.. the above diagrams... its > maximum cable length and number of switches that you can connect are > all true if and only if your network topology have collisions... > normally you have collisions in your network if it is configured as > *half* duplex... > > you are limited by the distance of the diagrams above because of > *round trip collision delay* that must conform with the 802.3 > specification... > > but good news.. everything changed when full duplex came... ethernet > is using carrier sense multiple access / collision detection or > CSMA/CD access method... CSMA/CD is not CSMA/CD anymore because there > is no more to sense the carrier before transmitting to avoid collision > and no collision anymore if it is under full duplex mode :-> > > with that.. under full duplex mode.. there is no more to worry about > round trip collision delay... so therefore... you can connect two or > more switches to extend your network as long as the maximum distance > cable used is within its distance specification and make sure that the > ports are configured in full duplex mode.. > > fooler. > _________________________________________________ > Philippine Linux Users' Group (PLUG) Mailing List > http://lists.linux.org.ph/mailman/listinfo/plug > Searchable Archives: http://archives.free.net.ph > _________________________________________________ Philippine Linux Users' Group (PLUG) Mailing List http://lists.linux.org.ph/mailman/listinfo/plug Searchable Archives: http://archives.free.net.ph
