The passive-interface command works differently with the
different IP routing protocols that support it.
-
RIP– With, routing updates are received, but are not sent.
-
EIGRP – With EIGRP, the router stops sending hello packets on
passive interfaces. When this happens, EIGRP cannot form neighbor adjacencies
on the interface, and routing updates can neither be sent nor received.
-
OSPF – With OSPF, routing information is neither sent nor received
on a passive interface. The network address of the passive interface appears as
a stub network in the OSPF domain.
Debugs and Verification
Figure
shows the output
of the show ip protocols command, which shows the outgoing
interface is defined as passive.
Figure
shows
the configuration of router R1, which shows that the outgoing interface is
defined as passive.
Solution
Figures
and
confirm
that the interface Ethernet 0 is defined as passive, so router R1 is not
sending any updates on Ethernet 0. Sometimes, it is desirable for some networks
to be advertised and others to be filtered. In this situation, a
distribute-list out would be a better solution.
In
this example, the assumption is that the passive-interface
was configured by mistake, and this command needs to be removed to solve this
problem. Figure
shows the new
configuration to solve this problem.
Figure
shows the
routing table entry on router R2 after fixing the problem.