received on different ports. You can avoid this problem by creating redundant paths using port trunks or spanning
tree.
Figure 82: Example: of duplicate MAC address
Disabled overlapping subnet configuration
Previous software versions allowed configuration of VLAN IP addresses in overlapping subnets which can cause
incorrect routing of packets and result in IP communication failure. As of software version WB.15.09, overlapping
subnet configurations are no longer allowed. An overlapping subnet is determined by the configuration order. The
subnet that is configured first is valid, but any subsequent IP addresses that overlap are not allowed.
When the switch is booted into software version WB.15.09 or later, and the configuration file includes overlapping
subnets, the following occurs:
• The event log provides an error message in the format:
ip: VLANx : IP initialization failed for vlan x.
For a multinetted VLAN (multiple IP addresses assigned to the VLAN), only the IP addresses that are
overlapping subnets are removed. The other IP addresses on the VLAN are retained and function correctly.
The error message can be somewhat misleading; the IP addresses on the VLAN that are not overlapping are
initialized correctly.
• The output of the show ip command correctly indicates that the overlapping IP address does not exist on the
VLANs that have error messages in the event log.
• The output of the show running-config command incorrectly indicates that the overlapping IP address is
configured. In
Figure 83: An IP address that is not actually configured on the VLAN on page 473, the IP
address shown in VLAN6 is not actually configured on the VLAN; it has been removed.
Figure 83: An IP address that is not actually configured on the VLAN
switch(config)# show running-config
.
.
.
vlan 5
name “VLAN5”
ip address 11.22.33.1 255.0.0.0
exit
vlan 6
name “VLAN6”
ip address 11.23.34.1 255.255.255.0
exit
Chapter 13 Troubleshooting 473
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