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Verifying the Installation 55
A few of the connection options in Figure 3-3 come up on a regular basis:
·
Frame Relay--Frame Relay connections are serial connections only. EIA/TIA-232, EIA/
TIA-449, V.35, and X.21 are the supported serial connections for Cisco routers. V.35 is
the most common connection type for most areas; however, popularity varies. These
connections make use of electrically specific transition cables that should be purchased
along with the router.
·
ISDN BRI--BRI connections are known as 2B+D connections. However, 1B+D and
0B+D implementations are available for deployment. An ISDN BRI connection makes
use of Category 5 cabling to connect to the demarc. It may be necessary to provide an
external NT1 if one is not integrated into the router. You can tell whether one is integrated
by the label on the interface. A BRI interface with an integral NT1 is labeled as BRI U,
and a BRI interface without an integral NT1 is labeled as BRI S/T. These connections
make use of RJ-45 cables, which are typically Category 4 or 5 in quality.
·
ISDN PRI--This implementation varies, based on geographic location. Based on ISDN
technology, PRI makes use of T1 or E1 characteristics. Outside of North America, you
will very likely encounter E1 PRI. Inside of North America, you will encounter T1 PRI.
The primary difference between the two is the number of bearer channels. T1 PRI makes
use of 23B+D connectivity, and E1 PRI makes use of 30B+D connectivity. E1 PRI
obviously has a significantly higher bandwidth capacity than T1 PRI. These connections
make use of category 4 or 5 RJ-45 cables.
·
Asynchronous--These connections make use of RJ-11 cables. They are dial-up
connection interfaces designed to accept calls from remote users. If utilizing external
modems, EIA/TIA-232 cables are necessary to connect the modem to the router. It is
feasible to have all modems internal to the router as well.
Verifying the Installation
The task of verifying physical connectivity is usually an easy one. If all is well, there is an LED
on the front of the router (or on the back by the interface in question) that is green. If it's not
green, it's time to figure out why.
During the boot process, the LEDs may flash green. This is completely normal. Other models
of Cisco devices have an amber colored light during the boot sequence. However, once the
router has booted, all active and functioning LEDs should turn to solid green. You'll hear the
phrase "Green is good" over and over in many Cisco classes and environments.
For most routers, identifying the LEDs is the difficult part. This section focuses on some of the
routers discussed in previous sections to give you some idea of where to find the proper LEDs
for your specific needs. For additional information, refer to the installation guide that came with
your specific router.