Table of Contents
Advertisement
26 IPv4 Interfaces
26.1 Description
You can set IPv4 addresses for VLANs so that the Switch can use SNMP, Telnet, and FTP
communications for management use. To allow the Switch to communicate to other
subnets, static routes must be configured for the subnets.
Also, the Switch detects duplication of IPv4 addresses set for VLAN interfaces. There is no
configuration for enabling duplication detection. Setting IPv4 addresses for VLAN
interfaces automatically enables duplication detection for the VLAN interfaces.
(1) Detecting duplication of IP addresses
The Switch checks for the duplication of IP addresses set for the VLAN interfaces on the
Switch. The Switch sends a gratuitous ARP for each VLAN interface, and checks whether
the source IP addresses in the received ARP packets are duplicated.
(a) Gratuitous ARPs sent from the Switch
The Switch sends a gratuitous ARP in which the IP address set for the VLAN interface on
the Switch is set in the Target Protocol Address field. Each time a VLAN interface goes up,
one gratuitous ARP packet is sent.
(b) ARP packets checked for duplication
All ARP packets (not only gratuitous ARP response packets) that are received normally are
checked for duplication as long as the following conditions are met:
The destination MAC address is the unicast address for a VLAN on the Switch, or a
broadcast address.
The packet is not discarded by a Spanning Tree Protocol, access lists, dynamic ARP
inspection, or authentication method on the Switch.
An IP address has been set for the VLAN interface that receives the packet.
(c) Detection conditions
A duplicate IP address is detected when all the following conditions are met:
The source MAC address in the ARP payload is other than the unicast MAC address
for the Switch (common to all VLANs).
The source IP address is the IP address set for the Switch.
(d) Operation when a duplication is detected
When the duplication of an IP address is detected, the Switch outputs an operation log
containing the following information.
Table 26-1 Operation log information output when a duplication of an IP address is
Information
Description
included in a
log
VLAN ID
Interface number of the VLAN on which the duplicate IP address was detected
IP address
IP address whose duplication was detected
MAC address
MAC address of the remote device that has a duplicate IP address (source MAC address in
the ARP payload)
However, if an operation log was output for the same IP address within the past 10 minutes,
a new operation log will not be output.
458
detected
Advertisement
Table of Contents
