Troubleshooting guide

3. Troubleshooting Functional Failures During Operation
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1. Log in to the Switch.
2. Use the
show ipv6 neighbors command to check the status of address resolution (whether
NDP entry information exists) between the Switch and the neighboring device.
3. If the address with the neighboring device has been resolved (NDP entry information exists),
see (4) Checking the unicast routing information.
4. If the address has not been resolved (no NDP entry information exists), check whether the IP
network settings between the neighboring device and the Switch are correctly set to allow
communication between them.
(4) Checking the unicast routing information
You need to check the routing information obtained by the Switch if (a) communication is still
disabled after address resolution with the neighboring device is completed, (b) communication is
disabled on the route to the remote device, or (c) the route to the remote device has a problem. To
carry out the check, do the following:
1. Log in to the Switch.
2. Use the
show ipv6 route command to check the routing information obtained by the Switch.
3. If the routing information obtained by the Switch does not contain the routing information
about the interface that caused the communication failure or contains an incorrect address of
the interface's next hop, see 3.11 IPv6 unicast routing communication failures.
4. If the routing information obtained by the Switch contains routing information about the
interface that caused the communication failure, the interface might have a problem with the
functionality shown below. That functionality must be checked.
• Filters and QoS functionality
See (5) Checking the filters and QoS configuration information.
• IPv6 DHCP relay
See (6) Checking the IPv6 DHCP relay configuration information.
(5) Checking the filters and QoS configuration information
Even if there is no physical fault on the Switch and the routing information is correctly set,
communication might not be possible. In this case, filtering might have been set to discard only
specific packets or packets might have been discarded by bandwidth monitoring, drop control, or
the QoS control shaper.
Therefore, make sure that the setting conditions for filters and QoS control in the configuration are
correct, and that bandwidth monitoring, drop control, or the shaper is used appropriately in the
system configuration. For details about the procedure, see 3.25 Communication failures in filters
and QoS configurations.
(6) Checking the IPv6 DHCP relay configuration information
If many of the prefixes or addresses to be leased are left on the IPv6 DHCP server, it can be
assumed that the prefixes or addresses cannot be assigned to clients due to incorrect configuration
settings for the IPv6 DHCP relay.
The following describes the operations for checking the configuration.
1. Check whether the IPv6 address of the IPv6 DHCP server or IPv6 DHCP relay, or the
interface to the network in which the IPv6 DHCP server exists, is specified by the
ipv6 dhcp
relay destination configuration command.
2. Check whether the
ipv6 dhcp relay destination configuration command is set for the client
interface.
3. Check whether the IPv6 address (or interface) of the IPv6 DHCP server that must lease a