Re: Loopback Advertisement in OSPF

From: Piotr M (pitt2k@gmail.com)
Date: Tue Dec 30 2008 - 07:39:27 ARST


Not true. When you do that, the Loopback interface has still OSPF
LOOPBACK network type, so it still advertises prefix as /32.

Topo: R3 -- R4

R4#sh run int lo0
Building configuration...

Current configuration : 79 bytes
!
interface Loopback0
 ip address 4.4.4.4 255.255.255.0
 ip ospf 1 area 0
end

R4#sh ip ospf int lo0
Loopback0 is up, line protocol is up
  Internet Address 4.4.4.4/24, Area 0
  Process ID 1, Router ID 4.4.4.4, Network Type LOOPBACK, Cost: 1
  Enabled by interface config, including secondary ip addresses
  Loopback interface is treated as a stub Host

R3#sh ip ro 4.4.4.4 255.255.255.0
% Subnet not in table

R3#sh ip ro 4.4.4.4 255.255.255.255
Routing entry for 4.4.4.4/32
  Known via "ospf 1", distance 110, metric 2, type intra area
  Last update from 10.1.1.4 on FastEthernet0/0, 00:00:49 ago
  Routing Descriptor Blocks:
  * 10.1.1.4, from 4.4.4.4, 00:00:49 ago, via FastEthernet0/0
      Route metric is 2, traffic share count is 1

Cheers,
PM

2008/12/30 Dinesh Patel <jedidinesh@googlemail.com>:
> How sure are we on this. If you advertise the loopback by doing:
> int loop 0
> ip ospf 1 area x
>
> then that fulfills the lab requirements to advertise the loopback and also
> gives a correct mask. I don't see how they could deduct points for this. Any
> views?
>
> Dinesh
>
>
> On Mon, Dec 29, 2008 at 6:20 PM, Piotr M <pitt2k@gmail.com> wrote:
>>
>> John,
>>
>> You need to configure ONLY those things which are clearly specified in
>> the task or in global "pre-tasks/ to do" section on the exam. If you
>> do something more/less you will loose your points.
>>
>> HTH,
>> PM
>>
>> 2008/12/29 John Edom <jedom123@gmail.com>:
>> > Hi,
>> >
>> > while OSPF configuration task, when we advertise loopback, network type
>> > should be configured point-to-point (for the sake of actual subnet mask)
>> > or
>> > configured only if task ask for it? If there any situation where task
>> > doesnt
>> > ask directly for this configuration but we have to ?
>> >
>> > Regards
>> >
>> >
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>> >
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>>
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>>
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