xStack DES-3800 Series Layer 3 Stackable Fast Ethernet Managed Switch
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IP Multinetting
IP Multinetting is a function that allows multiple IP interfaces to be assigned to the same VLAN. This is beneficial to the
administrator when the number of IPs on the original interface is insufficient and the network administrator wishes not to resize
the interface. IP Multinetting is capable of assigning another IP interface on the same VLAN without affecting the original
stations or settings of the original interface.
Two types of interfaces are configured for IP multinetting, primary and secondary, and every IP interface must be classified as
one of these. A primary interface refers to the first interface created on a VLAN, with no exceptions. All other interfaces created
will be regarded as secondary only, and can only be created once a primary interface has been configured. There may be five
interfaces per VLAN (one primary, and up to four secondary) and they are, in most cases, independent of each other. Primary
interfaces cannot be deleted if the VLAN contains a secondary interface. Once the user creates multiple interfaces for a specified
VLAN (primary and secondary), that set IP interface cannot be changed to another VLAN.
Application Limitation: A multicast router cannot be connected to IP
interfaces that are utilizing the IP Multinetting function.
NOTE: Only the primary IP interface will support the BOOTP relay agent.
IP Multinetting is a valuable tool for network administrators requiring a multitude of IP addresses, but configuring the Switch for
IP multinetting may cause troubleshooting and bandwidth problems, and should not be used as a long term solution. Problems
may include:
• The Switch may use extra resources to process packets for multiple IP interfaces.
• The amount of broadcast data, such as RIP update packets and PIM hello packets, will be increased.
IP Interface Settings
Each VLAN must be configured prior to setting up the VLAN’s corresponding IP interface.
An example is presented below:
VLAN Name VID Switch Ports
System (default) 1 5, 6, 7, 8, 21, 22, 23, 24
Engineer 2 9, 10, 11, 12
Marketing 3 13, 14, 15, 16
Finance 4 17, 18, 19, 20
Sales 5 1, 2, 3, 4
Backbone 6 25, 26
Table 8- 1. VLAN Example - Assigned Ports
In this case, six IP interfaces are required, so a CIDR notation of 10.32.0.0/11 (or a 11-bit) addressing scheme will work. This
addressing scheme will give a subnet mask of 11111111.11100000.00000000.00000000 (binary) or 255.224.0.0 (decimal).
Using a 10.xxx.xxx.xxx IP address notation, the above example would give 6 network addresses and 6 subnets. Any IP address
from the allowed range of IP addresses for each subnet can be chosen as an IP address for an IP interface on the switch. For this
example, we have chosen the next IP address above the network address for the IP interface’s IP Address:
