Cisco Cisco IOS Software Release 12.2(27)SBC

The interface IP address is unknown. The IP address is not configured or received through DHCP or 
IPCP negotiation.

Tracking the IP-routing state of an interface using the track interface ip routing command can be more 
useful in some situations than just tracking the line-protocol state using the track interface 
line-protocol command, especially on interfaces for which IP addresses are negotiated. For example, on 
a serial interface that uses the Point-to-Point Protocol (PPP), the line protocol could be up (link control 
protocol [LCP] negotiated successfully), but IP could be down (IPCP negotiation failed).

The track interface ip routing command supports the tracking of an interface with an IP address 
acquired through any of the following methods:

Conventional IP address configuration

PPP/IPCP

DHCP

Unnumbered interface

In the following example, the tracking process is configured to track the IP-routing capability of serial 
interface 1/0:

track 1 interface serial1/0 ip routing

Displays HSRP tracking information.