R3102-R3103-HP 6600/HSR6600 Routers Layer 2 - WAN Configuration Guide

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interface are directly connected, they can communicate in most cases, but sometimes with frequent
packet dropping and CRC errors.
• If the two ends are PPPoA, make sure that their IP addresses (should be in the same network segment)
and authentication parameters are correctly configured.
• If, according to the ping command, small packets can pass but big packets cannot, make sure that
the mtu configurations of the two router interfaces are the same.
ATM interface state error
Symptom
The interface state of ATM is DOWN.
Solution
Make sure that the optical fibers are correctly connected to ATM interfaces. There should be two optical
fibers, one for receiving information and one for sending information. The two are not exchangeable. If
they are wrongly connected, the interface state of ATM cannot be UP.
If two routers are connected back-to-back, check if neither of the two ATM interfaces enables internal
transmission clock. By default, routers use line clock. If two routers are connected back-to-back, one of
them should be configured as internal transmission clock with the clock master command.
PVC state is down while ATM interface state is up
Symptom
The interface state of ATM is UP, but the PVC state is DOWN.
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 that 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 that 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.