Passive interface command on RIP

[mahesh18]

Hi all,

This command below

passive-interface command give additional information to RIP, that it can't send updates via this particular interface ---

As per my understanding is this if we have 2 routers that are directly connected with each other and we enable this command on the interface of one of

routers then that router will not send any RIP updates to other router right?

secondly if these 2 routers are point to point connection we can ping directly conencted interfaces IP of  routers because they are directly connected even though there is no routing protocol running between these two right?

3rd thing when i run sh ip protocols on one of router it shows

Routing Protocol is "rip"

  Sending updates every 30 seconds, next due in 1 seconds

  Invalid after 180 seconds, hold down 180, flushed after 240

  Outgoing update filter list for all interfaces is not set

  Incoming update filter list for all interfaces is not set

  Redistributing: rip

  Default version control: send version 2, receive version 2

    Interface             Send  Recv  Triggered RIP  Key-chain

    FastEthernet0/0       2     2

  Automatic network summarization is in effect

  Maximum path: 4

  Routing for Networks:

    192.168.4.0

  Routing Information Sources:

    Gateway         Distance      Last Update

    192.168.4.2          120      00:23:38 ****************************************************

here last update time keeps on incrementing but  sh ip route does not show now that rip is running.

so this line means

Invalid after 180 seconds, hold down 180, flushed after 240

that after 240 secs router will flush the rip routes fron the routing table right?

but sh ip protocol  will always show rip as routing protocol as we have config the rip and last update time will keep on incrementing right?

thanks

mahesh

[Reza Sharifi · Accepted solution]

Hi Mahesh,

From the config guide:

To control the set of interfaces with which you  want to exchange routing updates, you can disable the sending of routing  updates on specified interfaces by configuring the

passive-interface

here is the link:

http://www.cisco.com/en/US/docs/ios/12_0/np1/configuration/guide/1crip.html

Correct, you do not need a routing protocol.  The interfaces are directly connected.  Now, if for example you add a loopback address to each router, you need a routing protocol or static router to reach the opposite router's loopback address.

The reason the interfaces/IPs do not show up in the RIP routing table is because they are directly connected and directly connected routes have a lower admin distance (1) which is preferred over rip which is 120.

yes

HTH

[shashank.kumar1]

hi

if in case we have 3 router in that case if we will run this commend on the middle router than how the other router will able to communicate on the either side (how first and second router will communicate to each other ). as  the middle router cant send the update and just can receive the updates.

[wasmer_anne · Accepted solution]

Mahesk,

A interface configured as passive will still receive RIP updates on that interface and the interface subnet will still be advertised out even if that interface will not send updates to its directly connected neighbour.

RIP passive interface does not work like OSPF where the passive interface statement stops forming neighbour adjacencies over that link.

By default the full update is every 30 seconds.

the routing table will always prefer directly connected routes.

[mahesh18]

Hi,

thanks to both of you for very good explanation

Mahesh

[jaiswalmanglam]

PASSIVE INTERFACE COMMAND on RIP

hi...

1.passive-interface command will block sending update only..it will never block receiving updates..

ex:-R1 and R2 are connected to each other,R1 having loopbacks and R2 also having loopbacks both are connected to each other through serial interfaces are..S0/0 and S0/0 respectively, and the network is 192.168.12.0 R1 from(.1) and R2 from(.2) in which we want R1 will not send its update to R2.so the command is:

config#router rip

----------------------#passive-interface S0/0

after doing that it will complete block sending its update to R2.

2.if we want that R1 send its update to R2 but not send its update to all other loopback which are connected to behind R2,so the command is:

config#router rip

----------------------#passive-interface S0/0

----------------------#neighbour 192.168.12.2

by using neighbour command it send update to only its neighbour which is advertising into it like (192.168.12.2) and other will be block..