Cisco ME 3800x and ME 3600x Switches Software Configuration Guide, Cisco IOS Release 15.4(3)S

Prerequisites for Auto-IP

• Link Layer Discovery Protocol (LLDP) must be enabled on the device before enabling the auto-IP functionality on a node interface.

Auto-IP on an EtherChannel

• When you configure auto-IP on an EtherChannel, ensure that LLDP is enabled on the member interfaces of the EtherChannel.
• Auto-IP configuration on an interface must be removed before moving an interface into an EtherChannel.

Auto-IP on VRF interfaces

• If you intend to configure auto-IP on an interface for a specific virtual routing and forwarding instance (VRF), then ensure that the interface is presently within the VRF. If you enable auto-IP on an interface and then associate the interface to a VRF, the auto-IP settings on the interface will be cleared, and you will have to enable the auto-IP feature on the VRF interface again.

Restrictions for Auto-IP

• Auto-IP addresses must not contain an even number in the last octet (such as 10.1.1.2, where the number in the last octet is 2).
• Auto-IP ring configuration should be manually removed before:

– deleting the sub-interfaces or removing the encapsulation from the sub-interfaces.

– moving the interface into ether-channel.

– moving the interface into a different VRF from the global/default VRF.

Auto-IP on an EtherChannel

• Auto-IP configuration on an interface is not retained when the interface is moved from one virtual routing and forwarding instance (VRF) to another, including the global VRF.
• Interface nodes in different VRFs cannot be configured for the same ring. Ensure that the nodes you select belong to the same VRF.
• If a VRF address family is IPv6, you cannot configure auto-IP on the interfaces within the VRF. You can configure auto-IP on a VRF interface if the VRF address family is IPv4.

Auto-IP on VRF interfaces

• Auto-IP configuration is not possible on a Switch Virtual Interface (SVI) with more than one physical interface. The SVI physical interface must be an access port or trunk port with only one associated VLAN or a bridge domain interface (BDI).

Auto-IP on EtherChannel interfaces

• Auto-IP configuration can be done on an EtherChannel interface, but not on a member interface of the EtherChannel.

Overview

For the auto-IP feature to work, Link Layer Discovery Protocol (LLDP) has to be enabled. LLDP supports a set of attributes that it uses to discover neighbor devices. These attributes contain type, length, and value descriptions, and are referred to as a Type Length Value (TLV).

In a ring topology, two network-to-network interfaces (NNIs or node interfaces) of a device are used to be part of a ring. The auto-IP feature is an automatic method to provide IP addresses to the node interfaces inserted into a ring. One node interface is designated as the ‘owner’ interface and the other as the ‘non-owner’ interface.

For a ring to function as an auto-IP ring, you must enable the auto-IP functionality on all the node interfaces within a ring.

Note The 2 node interfaces which are designated to be part of a ring must be configured with the same auto-IP address.

Before insertion, the interfaces are not designated as ‘owner’ and ‘non-owner’. After insertion, the auto-IP TLV is exchanged between the neighbor devices. During this initial negotiation with the adjacent device interfaces, ‘owner’ and ‘non-owner’ interfaces are determined automatically.

Note Auto-IP address is used for allocation purposes only and not used as an IP address for a node interface until the IP address is configured on an interface.

After a device is inserted into a ring, the auto-IP address configured for the device (such as 10.1.1.1) is assigned to the owner interface for the '/31' subnet. An owner interface has a priority 2 in the auto-IP TLV, and a non-owner interface has priority 0 in the auto-IP TLV. If there is no assigned IP address on the ring interface (before the node is inserted into a ring), then the ring interface has priority 1 in the auto-IP TLV.

The IP negotiation is based on priority; the higher value of priority wins the negotiation. If the priority is equal, then IP negotiation fails. This typically means incorrect configuration or wiring. In such a scenario, you must make sure the configuration and wiring is proper.

For more information about auto-IP feature, see Information About Auto-IP.

For more configuration steps, see How to Configure Auto-IP.

For information on CLI commands, see Cisco IOS IP Addressing Services Command Reference and Cisco IOS Master Command List, All Releases.

Supported Interfaces

Auto-IP feature is supported on the following interfaces:

• Ethernet interfaces and sub-interfaces
• Ether channel/bundle interfaces
• VRF
• SVI
• Port-channel

Configuring Auto-IP

Beginning in privileged EXEC mode, follow these steps to configure Auto-IP:

	Command	Purpose
Step 1	enable	Enables privileged EXEC mode. Enter your password if prompted.
Step 2	configure terminal	Enters global configuration mode.
Step 3	lldp run	Enables Link Layer Discovery Protocol (LLDP) for the device.
Step 4	interface type number	Specifies an interface type and number, and enters interface configuration mode.
Step 5	auto-ip-ring ring-id ipv4-address auto-ip-address	Configures the auto-IP address on the specified interface.
Step 6	exit	Exits interface configuration mode and enters global configuration mode.
Step 7	interface type number	Specifies an interface type and number, and enters interface configuration mode.
Step 8	auto-ip-ring ring-id ipv4-address auto-ip-address	Configures the auto-IP address on the specified interface.
Step 9	ip address interface-ip-address subnet-mask	Configures the IP address on the specified interface. Note The specified interface is designated as the owner interface of the seed device.
Step 10	end	Returns to privileged EXEC mode.
Step 11	show auto-ip-ring [ring-id][detail]	Displays auto-IP information.

Configuration Example for Auto-IP