User's Manual

12 Troubleshooting
APCD-LM043-4.0 151
12.4 General Troubleshooting Information
Table 36 provides troubleshooting tips related to general problems that you may be having
with trying to operate over the network.
Network Address Translation
If, from an affected host (PC, EUM, or CCU), you find that you can ping the gateway router
inside or outside addresses, but cannot ping beyond the gateway router, then you may want to
have a look at the operation of the router’s network address translation (NAT). In this case,
bring up the router NAT translation table, according to the manufacturer’s instructions, and
check that the host IP address is being properly translated in accordance with the NAT
scheme that you have implemented. If it is not being properly translated, then you must reset
or clear the NAT translation table in accordance with the manufacturer’s instructions.
Table 36 General Network Problems
Symptom Potential Causes
ARP table mismatches Network devices maintain an ARP table that matches an IP
address with a MAC address. Every network device has a
unique MAC address. If one network device is replaced by
another, and the new device uses the same IP address as
the old one, all devices on the network will have an incorrect
ARP table. All the network device ARP tables still have the IP
address pointing to the MAC address of the old device. This
is a temporary problem, as ARP tables are regularly flushed
and rebuilt. However, when swapping devices, this could
cause a situation where the new device cannot be pinged or
accessed until the ARP tables of other devices on the
network have adapted to the new configuration. This could
take from a few seconds to a few minutes.
IP address conflict If two network devices have the same IP address, immediate
and critical network problems result. Often, both devices shut
down.
Network router not configured correctly
for new network
When adding a wireless network to an existing Ethernet
network, some routing changes may be necessary to the
main gateway router of the Ethernet network.
10 to 100 Mbps mismatch between
networking equipment
CCUs and EUMs are forced to 10 Mbps on the Ethernet side.