From: William Lijewski (ccie8642@hotmail.com)
Date: Fri Oct 03 2003 - 13:14:10 GMT-3
Setting the Loopback as passive is basically going to stop the router from
sending updates to the Loopback. Take a look at the 'debug ip rip' output
below. This one is when the Loopback is not set as passive.
r1#debug ip rip
RIP protocol debugging is on
r1#clear ip route *
r1#
1d13h: RIP: sending request on Loopback0 to 255.255.255.255
1d13h: RIP: sending request on Ethernet0 to 255.255.255.255
r1#
1d13h: RIP: sending v1 flash update to 255.255.255.255 via Ethernet0
(10.100.10.
1)
1d13h: RIP: build flash update entries
1d13h: subnet 10.1.1.0 metric 1
1d13h: RIP: sending v1 flash update to 255.255.255.255 via Loopback0
(10.1.1.1)
1d13h: RIP: build flash update entries
1d13h: subnet 10.100.10.0 metric 1
r1#
1d13h: RIP: sending v1 update to 255.255.255.255 via Ethernet0 (10.100.10.1)
1d13h: RIP: build update entries
1d13h: subnet 10.1.1.0 metric 1
1d13h: RIP: sending v1 update to 255.255.255.255 via Loopback0 (10.1.1.1)
1d13h: RIP: build update entries
1d13h: subnet 10.100.10.0 metric 1
Notice how its sending updates to the Loopback and the Ethernet. Now we'll
make the Loopback passive:
r1(config)#router rip
r1(config-router)#passive-interface lo 0
r1(config-router)#end
r1#clear ip route *
r1#
1d13h: RIP: sending request on Ethernet0 to 255.255.255.255
r1#
1d13h: RIP: sending v1 flash update to 255.255.255.255 via Ethernet0
(10.100.10.
1)
1d13h: RIP: build flash update entries
1d13h: subnet 10.1.1.0 metric 1
r1#
1d13h: RIP: sending v1 update to 255.255.255.255 via Ethernet0 (10.100.10.1)
1d13h: RIP: build update entries
1d13h: subnet 10.1.1.0 metric 1
Now that we have made the Loopback passive RIP is no longer sending updates
to the Loopback. Were saving the router a little bit of work this way. The
Loopback address will still be sent out to our neighbors, the router just
isn't going to spend time sending usless updates.
Bill Lijewski
CCIE #8642
Network Learning Inc
5 Day R&S CCIE Bootcamp Instructor
>From: k c <jwongccie@yahoo.com.hk>
>Reply-To: k c <jwongccie@yahoo.com.hk>
>To: ccielab@groupstudy.com
>Subject: passive interface lo
>Date: Fri, 3 Oct 2003 19:36:40 +0800 (CST)
>
>I have seen the command "passive interface lo0" configured in some routing
>protocols like rip, eigrp, ospf, isis. What does this mean? Loopback is not
>a physical interface, why make it passive? What is the theory behind?
>
>!u&V%*(+ &V%k(+!v=l)G VoiceMail Ew*o5|....
>http://voicemail.yahoo.com.hk
>
>***Get your CCIE and a FREE vacation: Shop.GroupStudy.com***
>_______________________________________________________________________
>Please help support GroupStudy by purchasing your study materials from:
>shop.groupstudy.com
>
>Subscription information may be found at:
>http://www.groupstudy.com/list/CCIELab.html
This archive was generated by hypermail 2.1.4 : Mon Nov 24 2003 - 07:52:56 GMT-3