Cisco Support Community
Community Member

Query regarding passive-interface

If i configured passive interface on serial0 of R1, then what will happen.

1.) Would R1 and R2 be able to exchange hello packets.

2.) Would R1 be able to receive route updates from R2.

3.) If Pc1 want to communicate with pc2,then will it be ping,telnet....

4.) if we want to copy some data from pc2 to pc1,is it possible... doubt is data will come from R2 to R1, will data will pass through passive interface,



Community Member

Re: Query regarding passive-interface


The "passive-interface" command behaves differently for different routing protocol.

E.g. for RIP, the router will not advertise routing info out a passive interface, but still can listen to routing updates on that interface.

For EIGRP, the command will deter neighbor adjacencies from being established at all. So no routing info will be exchanged.


Thank you.


Lim TS

Hall of Fame Super Gold

Re: Query regarding passive-interface

The question in the original post about sending and receiving hello packets imply that the router would be using a protocol like OSPF or EIGRP. And in fact I believe that the results in the environment in the drawing would be the same if the protocol was RIP. If the serial interface is configured as passive then no hello is sent (and for RIP no update is sent). So for all protocols (RIP, OSPF, EIGRP) the result is that neither router would have a route to the LAN of the other router.

The original post also had some questions about the ability of PC1 and PC2 to communicate. The answer depends on an understanding of the environment. In particular it depends on whether any other routing information is present. If the routers had static routes to the LAN of the other router (for example) then the PCs would communicate quite successfully. They could ping, or telnet, or exchange data quite well. Passive interface does not stop data packets from going through the interface. But passive interface stops dynamic routing protocols from exchanging information over the interfaces. If there were no routes to the other LAN then, obviously, the PCs would not be able to communicate with each other.



CreatePlease to create content