Users Guide

Layer 3 Routing Commands 1511
route will never be installed in the routing table because the next hop is not
in a local subnet. If a static route is configured on R1 using R2’s IP address as
next hop, the static route will be installed in the routing table. R1 will ARP for
the next hop address. R2 will ignore the ARP Request because the source IP
address is not in a local subnet.
It is a misconfiguration to enable OSPF on both ends of an unnumbered
interface without setting the OSPF network type to point-to-point. Each
router will reject its neighbor’s HELLOs because the source IP address is not
in a local subnet. Adjacencies never progress beyond the INIT state.
If three or more routers are connected to the same subnet/broadcast domain
and all are configured to treat the Ethernet interface as a point-to-point link,
adjacencies may not form. The OSPF database description packets intended
for a specific neighbor will be processed by all neighbors, causing errors that
reset adjacencies.
Command History
Introduced in version 6.2.0.1 firmware.
Example
console(config-if-vlan1)#ip unnumbered 10.130.14.55
ip unnumbered gratuitous-arp accept
This command enables installation of a static interface route to the
unnumbered peer upon receiving a gratuitous ARP.
Syntax
ip unnumbered gratuitous-arp accept
no ip unnumbered gratuitous-arp accept
Default Configuration
The default mode is accept.
Command Mode
Interface (VLAN) Configuration