215
Solution
Determine if this fault results from enabling OAM F5 Loopback cell transmission and retransmission
detection or OAM continuity check. When two ATM devices are connected, the VPI/VCI value of the
PVCs on the two devices must be the same. If OAM F5 cell transmission and retransmission
detection or OAM continuity check is enabled, and the VPI/VCI value of the remote node (connected
directly with the local node) is not the same as the local node, the local PVC state cannot change into
UP.
Ping failure after PPPoA configuration
Symptom
The PVC state is UP, but after applications like IPoA are configured, the remote node cannot be
successfully pinged.
Solution
Make sure the remote node supports the same application as configured on the local node. For
example, if the local node uses PPPoA, the remote node should also use PPPoA.
If the remote node supports the same application configured on the local node, make sure the two
sides use the same type of AAL5 encapsulation protocol. For example, if one side uses SNAP
whereas the other uses MUX, they cannot communicate. You can enable the packet debugging
function of ATM to get some clues.
Packet loss and CRC errors and changes of interface state
Symptom
Two routers are connected back-to-back, and a ping between them is successful, but sometimes
there are large amount of packets lost and frequent CRC errors, or the interface state alternates
between UP and DOWN.
Solution
Check the ATM interfaces of the two nodes to see if their types are the same (both are multimode
fiber interface or both are single-mode fiber interface). If their types are different, you should change
one of them. In most cases, when a multimode fiber interface and a single-mode fiber interface are
directly connected, they can communicate, but sometimes with the mentioned faults.
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