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Webcast-Catalyst9k
New Member

OSPF loopback addess..

Hello

To advertise the loopback route as full subnet mask (not /32), I heard there are 3 different way to deploy this. Excetp using "ip ospf network", "redistribute" how do i configure this.

1 ACCEPTED SOLUTION

Accepted Solutions
VIP Purple

Re: OSPF loopback addess..

Hello,

another way to advertise the /32 loopback as an e.g. /24 would be to use area summarization (on the ABR). If your Loopback interface address is 172.16.20.1/32, you could advertise it as a /24 by using the following commands:

network OSPF 1

area 5 range 172.16.20.0 255.255.255.0

HTH,

GP

5 REPLIES
VIP Purple

Re: OSPF loopback addess..

Hello,

another way to advertise the /32 loopback as an e.g. /24 would be to use area summarization (on the ABR). If your Loopback interface address is 172.16.20.1/32, you could advertise it as a /24 by using the following commands:

network OSPF 1

area 5 range 172.16.20.0 255.255.255.0

HTH,

GP

Gold

Re: OSPF loopback addess..

You would still need to have the loopback interface "covered" through a network statement in this case, though. You can't summarize it if it's not in the ospf database to start with.

:-)

Russ.W

Gold

Re: OSPF loopback addess..

interface loopback 0

ip ospf network-type point-to-point

And then include the interface through a network statement.

:-)

Russ.W

New Member

Re: OSPF loopback addess..

Hi Russ.

Im looking for the other way except "ip ospf net", "redistribute" to resolve this,^^ do you have any idea about this?

Gold

Re: OSPF loopback addess..

Hmmm.... There are only two ways to get a route into OSPF: redistribution, or a network statement. One brings the route in as an external, the other as an internal. So, you can:

-- Set the loopback up as a /24, and redistribute it, for an external.

-- Set the loopback up as a /24, configure it as a point-to-point, and then use a network statement to inject it into ospf.

I'm not certain why one of those two methods wouldn't work (?).

:-)

Russ.W

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