Information Technology Reference
In-Depth Information
Table22-1 Total Connectivity Loss Between Two ATM-Attached Routers (continued)
One of the
interfaces is
down/down.
(continued)
The scrambling is important in DS-3. It can be configured via
atm ds3-scramble
or
atm e3-scramble
in interface
configuration mode.
3.
Check the quality of the cable.
4.
Look for evidence of physical error in
show controller
of
the ATM device as well as
show atm pvc
output. Check the
PVC status. Check that you are not receiving AIS, for
example.
5.
If the physical side seems okay and you see the outgoing
traffic counters growing, check that you are actually
forwarding traffic out of the interface by loopbacking the
physical interface. You have two ways to do this:
•
Physically loop back the Tx to the Rx.
•
Use the possibilities of the ATM card to help you on this. In
configuration interface mode, enter:
Sevilla(config-if)#loopback diagnostic
When the loopback is in place, the interface must come back
up/up if the hardware is not faulty.
6.
When you have defined the loopback, try to
ping
yourself. If
the card is behaving well, you should be able do it. Make
sure that you have the right mapping defined.
There is a Layer 3
routing problem.
1.
Both interfaces are up/up. Check the appropriate routing
table (in the case of IP,
show ip route
).
Enter
show ip route a.b.c.d
, where
a.b.c.d
is the destination IP
address that you cannot reach. This IP address is reachable only
via the ATM PVC.
Check that the peer router (the router on the other side of the
PVC) is reachable.
2.
If the peer router is a reachable neighbor and the routing
table does not point to the ATM subinterface where the PVC
is defined for a given route, your problem likely is a routing
problem; refer to Chapter 7, “Troubleshooting TCP/IP.”
3.
There is a
mismatch in the
mapping of Layer
3 address of the
peer router.
There is no automatic mapping between a PVC and the Layer 3
address of the router reachable via the PVC.
This can be checked via the command
sh atm map
:
Ema#
sh atm map
Map list test : PERMANENT
ip 164.48.227.142 maps to VC 140
1.
Show controller output is specific to each ATM card. Often, valuable information can be deduced from
this output, but no generic description can be given.