Fixing Leased-Line Problems
most common problem with leased lines is poor performance. In most
situations, you need to work with the telephone company to fix the
Table 7-6 Common
The link does not start.
CSU biopolar violations (CSU BPVs) can be the cause. One end
of the link is set up for AMI lines. The other end is set up for ESF
bit–8 zero substitute (B8Zs).
If you are in the United States or
Canada, you can directly fix this problem from the menu of the CSU/DSU.
Check the CSU/DSU manufacturer's documentation for details.
In other locales, the provider might be responsible for fixing
The link has poor performance.
The pppd debug output shows CRC errors when
sustained traffic is on the link. Your line might have a clocking
problem, caused by misconfigurations between the telephone company
and your network.
Contact the telephone company to ensure that “loop clocking”
is in use.
On some unstructured leased lines, you might have to supply
clocking. North American users should use loop clocking.