Configuring IP Addressing

IP Configuration

Configure Multiple IP Addresses on a VLAN (Multinetting). You can configure one primary IP address per VLAN and up to seven secondary IP addresses for the same VLAN. That is, the switch enables you to assign up to eight networks to a VLAN.

Each IP address on a VLAN must be for a separate subnet.

The switch assigns the first IP address manually configured on a VLAN as the primary IP address. The switch then assigns any subsequent IP addresses (for other subnets) manually configured on the VLAN as sec­ ondary addresses.

If the primary IP address on a VLAN is configured for DHCP-Bootp, the switch does not accept secondary IP addresses on that VLAN. (DHCP operates only to provide primary IP addressing, and is not used for providing secondary IP addressing.)

The switch allows up to 512 secondary subnet address assignments to VLANs.

Syntax: [ no ] vlan <vlan-id> ip address <ip-address/mask-length> [ no ] vlan <vlan-id> ip address <ip-address> <mask-bits>

For example, if you wanted to multinet VLAN_20 (VID = 20) with its primary IP address and two secondary IP addresses shown below, you would perform steps similar to the following. (For this example, assume that the primary IP addressing is already configured.)

Status

VID

IP Address

Subnet Mask

Primary

20

10.25.33.101

255.255.240.0

Secondary

20

10.26.33.101

255.255.240.0

Secondary

20

10.27.33.101

255.255.240.0

 

 

 

 

1.Go to VLAN 20.

2.Configure two secondary

IP addresses on VLAN 20.

3. Display IP addressing.

Note: A VLAN’s secondary IP entries are listed below the VLAN’s name and primary IP address.

In a show ip listing, the first IP address listed for a VLAN is always that VLAN’s primary IP address.

Figure 8-4. Example of Configuring and Displaying a Multinetted VLAN

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