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Chapter5 Configuring WAN Connections
Configuring a Serial Connection
5-12
Cisco Router and Security Device Manager 2.5 User’s Guide
OL-4015-12
Line Code This field configures the router for operation on binary 8-zeros
substitution (B8ZS) or alternate mark inversion (AMI) T1 lines. The
b8zs setting ensures density on a T1 or E1 line by substituting
intentional bipolar violations in bit positions 4 and 7 for a sequence
of eight zero bits. When the router is configured with the AMI
setting, you must use the data-coding inverted setting to ensure
density on the T1 line. The default is b8zs.
Data Coding Click inverted if you know that user data is inverted on this link, or
if the Line Code field is set to AMI. Otherwise leave this set to the
default value normal. Data inversion is used with bit-oriented
protocols such as HDLC, PPP, and Link Access Procedure,
Balanced (LAPB) to ensure density on a T1 line with AMI
encoding. These bit-oriented protocols perform “zero insertions”
after every five “one” bits in the data stream. This has the effect of
ensuring at least one zero in every eight bits. If the data stream is
then inverted, it ensures that at least one out of every eight bits is a
one.
Cisco SDM will set data coding to inverted if the line code is AMI
and there are no time slots configured for 56 kbps. If you do not
want to use inverted data coding with the AMI line code, you must
use the CLI to configure all time slots to 56 kbps.
Facilities Data Link (FDL) This field configures the router behavior on the Facilities Data Link
(FDL) of the Extended Superframe. When configured with att, the
router implements AT&T TR 54016. When configured with ansi, it
implements ANSI T1.403. When you choose both, the router
implements both att and ansi choices.When you choose none, the
router ignores the FDL. The default is none. If T1 or E1 framing
is set to sf, Cisco SDM will set FDL to none and make this field
read-only.
Line Build Out (LBO) This field is used to configure the line build out (LBO) of the T1
link. The LBO decreases the transmit strength of the signal by –7.5
or –15 decibels. It is not likely to be needed on actual T1 or E1 lines.
The default is none.
Table 5-10 Clock Settings Fields
Element Description