Chapter 18
Configuring IP Unnumbered Interface
Figure 18-2
1
Type
(byte 1)
Table 18-1
Table 18-1
Field
Type
Length
Reserved
NAS IP Address
Interface
Reserved
VLAN ID
IP Unnumbered Interface with Connected Host Polling
Note
This feature option is applicable to LAN and VLAN interfaces only.
In some cases, the host IP address is assigned statically. The IP Unnumbered Interfaces feature can learn
the static host IP address dynamically.
IP Unnumbered Configuration Guidelines and Restrictions
When using (or configuring) IP Unnumbered Interface, consider these guidelines and restrictions:
•
Format of the Agent Remote ID Suboption
Length
Reserved
(byte 2)
(bytes 3-4)
describes the agent remote ID suboption fields displayed in
Agent Remote ID Suboption Field Descriptions
For IP Unnumbered Interfaces, the following features are not supported:
Dynamic routing protocols
–
HSRP/VRRP
–
Static ARP
–
Unnumbered Interface and Numbered Interface in different VRFs
–
Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
IP Unnumbered Configuration Guidelines and Restrictions
NAS IP address
Interface
(bytes 5-8)
(byte 9)
Description
Format type. The value 2 specifies the format for use with this feature.
(1 byte)
Length of the Agent Remote ID suboption, not including the type and
length fields. (1 byte)
Reserved. (2 bytes)
IP address of the interface specified by the ip unnumbered command.
(4 bytes)
Physical interface. This field has the following format:
slot (4 bits) | module (1 bit) | port (3 bits).
For example, if the interface name is interface ethernet 2/1/1, the slot
is 2, the module is 1, and the port is 1. (1 byte)
Reserved. (1 byte)
VLAN identifier for the Ethernet interface. (2 bytes)
12 bytes
Reserved
VLAN ID
(byte 10)
(bytes 11-12)
Figure
18-2.
18-3