Troubleshooting guide

3. Troubleshooting Functional Failures During Operation
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device is impossible, the address might not have been resolved by ARP. To check the status of
address resolution between the Switch and the neighboring device, do the following:
1. Log in to the Switch.
2. Use the
show ip arp command to check the status of address resolution (whether ARP entry
information exists) between the Switch and the neighboring device.
3. If the address with the neighboring device has been resolved (ARP entry information exists),
see (6) Checking the unicast routing information.
4. If the address has not been resolved (no ARP entry information exists), check whether the IP
network settings between the neighboring device and the Switch are identical.
5. If DHCP snooping is used, packets might have been discarded by dynamic ARP inspection.
Check whether the setting conditions for DHCP snooping in the configuration are correct. For
details about the procedure, see 3.27 DHCP snooping problems.
(6) 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 during IPv4 unicast communication, 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. Execute the
show ip route command to check the routing information obtained by the
Switch.
3. For AX6700S, AX6600S, and AX6300S series switches, check whether packets are discarded
at the null interface. If
null0 is displayed for the sending interface that caused the
communication failure in the routing information, packets are discarded at the null interface.
Check the setting conditions for the static routing functionality in the configuration.
4. 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 3.8 IPv4 unicast routing communication failures.
5. 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.
• DHCP and BOOTP functionality
See (7) Checking the DHCP and BOOTP configuration information.
• Filters and QoS functionality
See (8) Checking the filters and QoS configuration information.
(7) Checking the DHCP and BOOTP configuration information
If IP addresses are assigned to neighboring devices by the relay or server functionality of DHCP
and BOOTP on the Switch, the IP addresses might have not been properly assigned.
Check whether the setting conditions for the relay or server functionality of DHCP and BOOTP in
the configuration are correct. For details about the procedure, see 3.7.2 IP addresses cannot be
assigned by the DHCP functionality.
(8) Checking the filters and QoS configuration information
Certain packets might have been discarded either by filtering or by bandwidth monitoring, drop
control, or the QoS control shaper.
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