Information Technology Reference
In-Depth Information
Table10-8
SDLC: Router Cannot Communicate with SDLC Device (continued)
Possible Problem
Solution
Physical layer
problem
(continued)
4.
If the interface or line protocol is still down, use a breakout
box to check the signals on the line.
Note:
On some Cisco platforms, such as the Cisco 7500 running
a recent Cisco IOS release, the output of the
show interfaces
command will indicate the state of line signals.
If the router is full-duplex DCE,
1
check for DTR
2
and RTS.
3
If
these signals are not high, proceed to Step 5. If these signals are
high, the interface should be up. If it is not, contact your
technical support representative.
On a Cisco 7500, if the breakout box shows that the DTR and
DTS signals are high, but
the show interfaces
command shows
that they are not, check the router cabling. In particular, make
sure that the 60-pin high-density cable is not plugged in to the
router upside-down.
If the router is half-duplex DCE, check for DTR. If DTR is not
high, proceed to Step 5. If DTR is high, the interface should be
up. If it is not, contact your technical support representative.
Note:
Half-duplex is not supported on Cisco 7000 series routers.
If the router is full- or half-duplex DTE, check for CD. If CD is
not high, proceed to Step 5. If CD is high, the interface should be
up. If it is not, contact your technical support representative.
5.
If the router is full-duplex DCE, make sure that the device is
configured for permanent RTS high. If the device does not
allow you to configure permanent RTS, set the signal high by
strapping DTR from the device side to RTS on the router side
(see Figure 10-5).
6.
If the router is DCE, it may be required to provide clock to
the device. Make sure that the
clock rate
interface
configuration command is present in the router
configuration. Use the
show running-config
privileged exec
command on the router to view the interface configuration.
The following example shows the clock rate information for
interface serial 0.
Example:
The following example sets the clock rate on the first serial
interface to 64000 bits per second:
interface serial 0
clock rate 64000
If the router is DTE, it should get clock from an external device.
Make sure that a device is providing clock properly. Make sure
that the clocking source is the same for all devices.
