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Forum Replies

  1. aujla3 says:

    hay rene, is there any way to make the default as passive and yet keep the interface that already has a neighbour as non passive? in other words is there a way to change the default on the router to passive on all interfaces except the onces that already have neighbours, without dropping the adj.


  2. Hi Ivaylo,

    It won’t prevent us from receiving the hello packets but I believe it does stop processing them. Here’s a little experiment I did with two routers, directly connected to each other:

    R1#debug ip ospf hello 
    OSPF hello debugging is on

    Now we can see we are sending and receiving hello packets:

    OSPF-1 HELLO Gi0/1: Send hello to area 0 from
    OSPF-1 HELLO Gi0/1: Rcv hello from area 0

    Let’s make the interface passive:

    R1(config)#router ospf 1
    R1(config-router)#passive-interface GigabitEthernet 0/1

    At this moment my debug is not producing any output anymore. Basically OSPF has been disabled on the interface. We are still receiving packets though:

    R1#debug ip packet 
    IP packet debugging is on
    IP: s= (GigabitEthernet0/1), d=, len 80, rcvd 0
    IP: s= (GigabitEthernet0/1), d=, len 80, input feature, packet consumed, MCI Check(109), rtype 0, forus FALSE, sendself FALSE, mtu 0, fwdchk FALSE

    Above you can see that we are receiving OSPF packets from

    About your other question:

    OSPF as an IGP (Interior Gateway Protocol) is typically used on our “own” networks. If you have a connection to your ISP for Internet access then all you need is a default route to them…we don’t run OSPF with the ISP.

    Hope this helps!


  3. Hi Ahmad,

    OSPF and EIGRP have one thing in common, they both establish a neighbor adjacency before they advertise any routing information. RIP doesn’t establish a neighbor adjacency, it just advertises routing updates.

    When you use the passive interface command for RIP then it stops advertising RIP routing updates on that interface. When you use it for OSPF or EIGRP, they won’t send any hello packets anymore so that it becomes impossible to establish a neighbor adjacency on the passive interface.


  4. Hello Monir

    When you indicate that an interface is passive, it means that any and all OSPF related messages are never sent out that interface. The connected network does participate in the OSPF process, that is, the connected subnet is advertised to other OSPF routers, but no hellos, LSAs or any other OSPF related packets are sent out that interface.

    The passive interface is configured on interfaces where you KNOW there is no OSPF router connected to it to receive any kind of OSPF information.

    I hope this has been helpful!


  5. Can you explain this statement - “All interfaces that have a network that falls within the range of the network command will be advertised in OSPF”.
    On R1, Fa 0/1 and Fa 0/0 are on a different subnet. Then how a network command on Fa 0/0 will send hello packets on Fa 0/1?

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