Solved: passive-interface with ospf

hanyawad · ‎12-04-2009

hello experts

when we issue the command (passive-interface) in ospf configuration on a specific interface, will this command prevent sending and receiving the update packet or prevent sending only and allow for receiving like rip and igrp, thankyou for your response

Labib

Jon Marshall · ‎12-04-2009

labibmakar wrote:

hello experts

when we issue the command (passive-interface) in ospf configuration on a specific interface, will this command prevent sending and receiving the update packet or prevent sending only and allow for receiving like rip and igrp, thankyou for your response

Labib

Passive interface on an OSPF interface will stop it forming any adjacencies/neighborships with other routers on that subnet so it never gets to the stage of sending or receiving routes.

Jon

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Giuseppe Larosa · ‎12-04-2009

Hello Labib,

OSPF, IS-IS and EIGRP have the neighbor state machine concept: they don't accept routes from a device that doesn't qualify as a neighbor so the passive-interface doesn't allow to have a device listening on the link, as it happens with older and simpler routing protocols like RIP and IGRP.

the passive-interface combined with other commands (protocol dependent) allows to advertise the IP subnet of the involved interface(s).

Hope to help

Giuseppe

View solution in original post

Jon Marshall · ‎12-04-2009

labibmakar wrote:

hello experts

when we issue the command (passive-interface) in ospf configuration on a specific interface, will this command prevent sending and receiving the update packet or prevent sending only and allow for receiving like rip and igrp, thankyou for your response

Labib

Passive interface on an OSPF interface will stop it forming any adjacencies/neighborships with other routers on that subnet so it never gets to the stage of sending or receiving routes.

Jon

Reza Sharifi · ‎12-04-2009

Hello Labib,

If you disable the sending of routing updates on an interface, the particular subnet will continue to be advertised to other interfaces, and updates from other routers on that interface continue to be received and processed.

HTH

Reza

Jon Marshall · ‎12-04-2009

sharifimr wrote:

Hello Labib,

If you disable the sending of routing updates on an interface, the particular subnet will continue to be advertised to other interfaces, and updates from other routers on that interface continue to be received and processed.

HTH

Reza

I agree that the subnet will be advertised to other neighbors but no updates on the passive-interface will be received and processed because no adjacency/neighborships can be formed therefore there will be no updates.

Or have i misunderstood what you wrote ?

Jon

Reza Sharifi · ‎12-04-2009

Jon,

You are right. It would be on the particular interface only and since there is no adjacency so there will be no other updates.

Thanks for the correction

Reza

Giuseppe Larosa · ‎12-04-2009

Hello Labib,

OSPF, IS-IS and EIGRP have the neighbor state machine concept: they don't accept routes from a device that doesn't qualify as a neighbor so the passive-interface doesn't allow to have a device listening on the link, as it happens with older and simpler routing protocols like RIP and IGRP.

the passive-interface combined with other commands (protocol dependent) allows to advertise the IP subnet of the involved interface(s).

Hope to help

Giuseppe