EIGRP Filtering with passive interface

Passive interface is used to suppress the EIGRP's hello. Take an example of R6, R6 router sending EIGRP's hello in all the interface whichever  matches the under the network command ip address. Lets see on R6 which all interface using EIGRP's hello

R6#sh ip eigrp int

IP-EIGRP interfaces for process 100

                        Xmit Queue   Mean   Pacing Time   Multicast    Pending

Interface        Peers  Un/Reliable  SRTT   Un/Reliable   Flow Timer   Routes

Fa0/0              1        0/0       196       0/1          553           0

Lo0                0        0/0         0       0/1            0           0

In the above output we came to know that EIGRP is sending  EIGRP's Hello on Interface fa0/0 and as well as on loopback0.

Its unnecessary to send EIGRP's Hello on those interface on which some other devices are connected which doesn't understand the EIGRP's Hello. We are wasting our bandwidth by sending this Hello.

To avoid this we can do filtering with passive-interface. Lets configure it.

R6#sh run | sec eigrp

router eigrp 100

 passive-interface default

 no passive-interface FastEthernet0/0

 network 150.6.0.0

 network 155.1.156.6 0.0.0.0

 no auto-summary

 neighbor 155.1.156.1 FastEthernet0/0

R6#sh ip eigrp int

IP-EIGRP interfaces for process 100

                        Xmit Queue   Mean   Pacing Time   Multicast    Pending

Interface        Peers  Un/Reliable  SRTT   Un/Reliable   Flow Timer   Routes

Fa0/0              1        0/0       140       0/1          513           0