Troubleshooting guide

3. Troubleshooting Functional Failures During Operation
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3.5 Layer 2 network communication failures
3.5.1 Layer 2 communication by VLANs is not possible
If Layer 2 communication is not possible when VLANs are used, isolate the cause of the
problem according to the failure analysis method described in the table below.
(1) Checking the VLAN status
Execute the show vlan or show vlan detail operation command to check the status of the
VLAN. The following describes the items that must be checked for each VLAN type.
(a) Items checked in common for all VLAN types
 Check whether the VLAN is configured correctly on the port.
 Check whether the correct mode is set for the port. If the expected port does not
belong to the default VLAN (VLAN ID 1), check whether:
 A port VLAN other than VLAN ID 1 is specified for the access VLAN or native
VLAN.
 The default VLAN is set in
allowed vlan for trunk ports.
 The port is specified as a mirror port.
(b) For protocol VLANs
 When you are using a protocol VLAN, execute the
show vlan operation command
and make sure the protocol has been configured correctly.
# show vlan
:
VLAN ID:100 Type:Protocol based Status:Up
Protocol VLAN Information Name:ipv4
EtherType:0800,0806 LLC: Snap-EtherType:
Learning:On Uplink-VLAN: Uplink-Block: Tag-Translation:
:
(c) For MAC VLANs
 When you are using a MAC VLAN, execute the
show vlan mac-vlan operation
command and make sure the MAC addresses allowed for communication that uses
the VLAN have been set correctly. In the example below, the value enclosed in
parentheses indicates the functionality used to register the MAC address.
[Functionality]
static: The MAC address is set in the configuration.
dot1x: The MAC address is set by the IEEE 802.1X functionality.
web-auth: The MAC address is set by the Web authentication functionality.
mac-auth: The MAC address is set by the MAC-based authentication
functionality.
# show vlan mac-vlan
:
VLAN ID:100 MAC Counts:4
0012.e200.0001 (static) 0012.e200.00:02 (static)
0012.e200.0003 (static) 0012.e200.00:04 (dot1x)
 Execute the show vlan mac-vlan operation command and make sure the MAC