Cisco Systems DOC-7814982 Environmental Guidelines for LRE Links

10-6
Catalyst 2950 Desktop Switch Software Configuration Guide
78-14982-01
Chapter 10 Configuring LRE
Configuring LRE Ports
Environmental Guidelines for LRE Links
The guid eline s for your LR E environm ent are based on the se factors:
•Maximum distanc e between th e LRE switc h and CPE devices—LRE runs on Category 1, 2, and 3
structur ed and unst ruct ur ed ca ble. The ma xim um dist anc e suppor t ed on th e LRE l ink i s fro m 35 00
to 5000 fee t, dependi ng on the pro file. The highe r the rate , the sho rter the dist ance . In buildings
where LRE traffic runs over bundled t elco cabl ing, th e maximu m distan ce is appr oximat ely 30
percent lower.
Each te rminated bri dge tap in a roo m can further r educe LRE lin k distance s by 300 feet. The q uality
of the cable, the size of the cable bundles, and cross talk within the bundle also can affect overall
reach.
•Site ty pe—If yo ur site ha s eith er a PB X pr oviding tele phone serv ice thr oug hout or h as dire ct
connect ions to the PSTN, you must iden tify the requiremen ts of your loc al public tele phone ser vice
provider.
If your site is a single building (or is a co n necte d set of buildings), c onsu lt a qu alified ele ctr icia n to
ensur e th at the w iri ng c onf orm s to t he a pp rop riat e r egul ation s fo r i ndoo r ci r cuits .
If your site h as sep arat e buildi ngs , y ou must de term ine how the building s ar e ca ble d to ea ch o th er.
Where the wiring between the LRE switch and CPE dev ice leaves the building (or the armored
condui ts c ertified f or inside wi ring sta ndard s), it m ust be pr otec ted a ga inst l ight nin g and sh orts to
high-voltag e power. Thi s protec tion might be provided by fuses or overvoltage pr otectors that
comply with local regulations for outside wiring protection. Consult an expert in local
telecommunications regulations for the details of this protection.
•Age and typ e of wirin g—You can estimate the type of wiring you hav e based on your site’s age and
type.
– Newer installation s less than 15 yea rs old often use Category 3 cable in bundles of 25 pairs.
There is no significant difference between 25-pair bundles and larger bundles.
– Older i nsta llat ions (h ote l, sc hool , hospi tal, c ommer cia l —Nort h A meri ca) 15 to 30 ye ars old
often use 24 AWG wiri ng with betw een 1 and 12 twis ts per foo t (similar to C ategory 1) in
bundles of 25 or more .
– Older installations (residential—North A meri ca) 15 to 30 yea rs old ofte n u se 26 AW G w iring
with be tw een 1 and 1 2 tw ist s p er f oot ( pos sibl y ty pe- 2) in bundles o f 1 00 or more .
– Older i nsta llat ions (E urope ) 15 to 30 year s o ld o ften u se 0.4 mm (si mil ar to 2 6 AWG ) wir ing
with be tw een 1 and 12 twi sts per f oot in bundle s of 10 0 o r more.
– Olde r in stal l atio ns (Asia ) 1 5 to 30 ye ars ol d of te n us e 0.4 mm (si mil ar to 26 AWG) wir in g wit h
betwee n 1 and 12 tw is ts pe r fo ot in bundle s o f 100 or m ore .
– Older i nsta llat ions over 30 year s o ld o ften u se heavy gau ge wi re ( 22 or 20 AW G) w ith no
significant twist. In many cases, the cabling is set into the fabric of the building. The cables
might be tightly or loosely bundled. For this estimate, assume that they are tightly bundled in
groups of 2 5 o r mor e.
•Cross talk (noise) and interference—LRE op er ate s w it h any n umb er of wi re s in a c a ble bi nd er
carrying the LRE signal. Anywhere from one wire pair to ev ery wire pair in the cable can carry LRE
signals at the same time. LRE operates in full cable binders and adjusts power levels on each LRE
link to maximize the performance of all connections.