Passive-interface command behavior in RIP, EIGRP & OSPF
Passive-interface command is used in all routing protocols to disable sending updates out from a specific interface. However the command behavior varies from one protocol to another.
In RIP this command will disable sending multicast updates via a specific interface but will allow listening to incoming updates from other RIP speaking neighbors.
This simply means that the router will still be able to receive updates on that passive interface and use them in the routing table.
In EIGRP the passive-interface command stops sending outgoing hello packets, hence the router can not form any neighbor relationship via the passive interface. This behavior stops both outgoing and incoming routing updates.
In OSPF the passive-interface has a similar behavior to EIGRP. The command suppresses hello packets and hence neighbor relationships.
I have only one final note here regarding sending unicast updates:
If you used the neighbor command under the RIP process, the router will send unicast updates as well as multicast updates.The passive-interface command must be used disable multicast updates and allowing only unicast.
In EIGRP the neighbor command disables multicast updates on an interface by default and allows only unicast updates.
Related posts:
- EIGRP timers (hello, hold-down and active)
- Automatic summarization in RIP and EIGRP
- EIGRP metric manipulation
- The ip route-cache command – Bury the hatchet series
- How-to: Avoid DNS lookup when mistyping a command
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June 6th, 2009 at 3:30 am
[...] Posted by Peter Kurdziel on June 5, 2009 Passive-interface command behavior in RIP, EIGRP & OSPF [...]
July 13th, 2009 at 10:34 pm
quite simple yet stronger and knowledgable tutorials.thx.
July 13th, 2009 at 10:50 pm
@Ripduman
, your feedback is really appreciated.
I am glad we are meeting you expectations
September 2nd, 2009 at 2:06 pm
Thank you so much for the useful info. Still I would like to know what is the difference between interface shut down and passive behavior in EIGRP & OSPF (My understanding is we can shut down the interface rather it configured as passive. Is any other advantage as being passive interface than it could be shut down). I am very much thankfull for your response.
September 3rd, 2009 at 7:35 pm
Jescibz,
If you shutdown the interface it will not be advertised by any routing protocol, the main reason behind using the passive interface command is to be able to advertise the interface subnet without forming adjacency on that interface.
If you still need more clarifications feel free to post your thoughts.
Wael
January 21st, 2010 at 4:50 pm
Hi everybody,
I have a similar question with Jescibz. I do not understand what is the difference between two interfaces that one of them is “passive interface” on eigrp, and the other one is not enabled for eigrp(do not send any Hello packets but not shutdown also)
We can do the same thing that “passive interface” command does by not enabling eigrp on this interface. Am I right?
Thanks…
January 24th, 2010 at 2:39 pm
ilkin,
passive interface advertise the network defined on this interface without participating in neighbor relationship on the interface; without passive interface the network defined on this interface will not be advertised.