We can consider passive-interface an indirect form of filtering.
R1#sh run | s rou
router rip
version 2
offset-list 10 in 5 Serial0/0
network 1.0.0.0
network 12.0.0.0
no auto-summary
R1#config t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#router rip
R1(config-router)#pass
R1(config-router)#passive-interface s0/0 -===condition 1
in this router we have
R1(config-router)#do sh ip int brief
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 unassigned YES NVRAM administratively down down
Serial0/0 12.1.1.1 YES NVRAM up up
FastEthernet0/1 unassigned YES NVRAM administratively down down
Serial0/1 unassigned YES NVRAM administratively down down
Loopback0 1.1.0.1 YES NVRAM up up
Loopback1 1.1.1.1 YES NVRAM up up
Loopback2 1.1.2.1 YES NVRAM up up
Loopback3 1.1.3.1 YES NVRAM up up
before condition 1
R2#sh ip route 1.0.0.0
Routing entry for 1.0.0.0/24, 4 known subnets
Redistributing via rip
R 1.1.0.0 [120/1] via 12.1.1.1, 00:02:46, Serial0/0
R 1.1.1.0 [120/1] via 12.1.1.1, 00:02:46, Serial0/0
R 1.1.2.0 [120/1] via 12.1.1.1, 00:02:46, Serial0/0
R 1.1.3.0 [120/1] via 12.1.1.1, 00:02:46, Serial0/0
after condition 1 applied i a few minutes
R2#sh ip route 1.0.0.0
% Network not in table
R2#
if we run debup ip rip we will see that s0/0 is rx routes but not sending over the interface
after so time we will not see any route from R1 or any other interface behind it .
if we applied in R2
R1# sh ip route 2.0.0.0
Routing entry for 2.0.0.0/24, 4 known subnets
Redistributing via rip
R 2.2.4.0/24 is possibly down,
routing via 12.1.1.2, Serial0/0
R 2.2.5.0/24 is possibly down,
routing via 12.1.1.2, Serial0/0
R 2.2.6.0/24 is possibly down,
routing via 12.1.1.2, Serial0/0
R 2.2.7.0/24 is possibly down,
routing via 12.1.1.2, Serial0/0
R1# sh ip route 2.0.0.0
