Product guide

Static Virtual LANs (VLANs)
Multiple VLAN Considerations
3. Assign the desired switch ports to the new VLAN(s).
4. If you are managing VLANs with SNMP in an IP network, the VLAN
through which you are managing the switch must have an IP address.
Refer to chapter 7, “Configuring IP Addressing”, in the Management and
Configuration Guide for your switch.
Multiple VLAN Considerations
Switches use a forwarding database to maintain awareness of which external
devices are located on which VLANs. Some switches, such as those covered
by this guide, have a multiple forwarding database, which means the switch
allows multiple database entries of the same MAC address, with each entry
showing the (different) source VLAN and source port. Other switch models
have a single forwarding database, which means they allow only one data-
base entry of a unique MAC address, along with the source VLAN and source
port on which it is found. All VLANs on a switch covered by this guide use the
same MAC address. Thus, connecting a Series 5300XL, 4200vl, 3400cl, or
6400cl (multiple forwarding database) switch to a single forwarding database
switch where multiple VLANs exist imposes some cabling and port VLAN
assignment restrictions. Table 2-5 illustrates the functional difference
between the two database types.
Table 2-5. Example of Forwarding Database Content
Multiple Forwarding Database Single Forwarding Database
MAC Address Destination
VLAN ID
Destination
Port
MAC Address Destination
VLAN ID
Destination
Port
0004ea-84d9f4 1 A5 0004ea-84d9f4 100 A9
0004ea-84d9f4 22 A12 0060b0-880af9 105 A10
0004ea-84d9f4 44 A20 0060b0-880a81 107 A17
0060b0-880a81 33 A20
This database allows multiple destinations
This database allows only one destination
for the same MAC address. If the switch
for a MAC address. If the switch detects a
detects a new destination for an existing
new destination for an existing MAC entry,
MAC entry, it just adds a new instance of
it replaces the existing MAC instance with
that MAC to the table.
a new instance showing the new
destination.
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