OSPF advertisement question

[mmercaldieze]

I am going to be setting up OSPF in my network and it has been while since I have done OSPF from the ground up.

if my address associated with the ospf link is 1.1.1.1 /24 and I ahve 3 other networks configured on it:

192.168.1.0/24

192.168.2.0/24

192.168.3.0/24

when I setup the ospf statement to advertise the routes do I just need the statement:

network 1.1.1.1 0.0.0.0 area 0

or do I need to do 

network 1.1.1.0 0.0.0.255 area 0

network 192.168.1.0 0.0.0.255 area 0

network 192.168.2.0 0.0.0.255 area 0

network 192.168.2.0 0.0.0.255 area 0

[Jon Marshall]

Do you mean you have secondary IPs on the same interface ?

If so then yes you need network statements for them all.

OSPF will only form an adjacency using the primary IP and you must be running OSPF on the primary IP for the secondary subnets to be advertised.

If you are not talking about secondary IPs can you clarify ?

Jon

[Masoud Pourshabanian]

Hello,

If you are going to advertise those three subnets, you need to configure them under Router OSPF command. Your configuration is correct. If there is no ospf neighbour in the subnet of 192.168.XX , use passive-interface[optional] to prevent OSPF sending hello packet on those subnets. Those subnet will be still advertised to the neighbors even if passive-interface is configured.

Router ospf 1

network 1.1.1.0 0.0.0.255 area 0

network 192.168.1.0 0.0.0.255 area 0

network 192.168.2.0 0.0.0.255 area 0

network 192.168.3.0 0.0.0.255 area 0

passive-interface  [interface name for subnet 192.168.1.0]

passive-interface  [interface name  forsubnet 192.168.2.0]

passive-interface [interface name  for subnet 192.168.3.0]

Hope it helps,

Masoud

[paul driver]

Hello

If you don't require specific router ids or passive interface you can also enable ospf without the router process via interface mode and still advertise the networks and negate the advertisement of secondaries if applicable at the same time

int x/x

ip ospf X area x ( secondaries none)

 if you do advertise via router process it suggested to be as specific as possible with your network statements

Ie: 

IP 192 168.1.1/24

router ospf  x

network 192 168.1.1  0.0.0.0 area x

       instead of

Network 192.168.1.0 0.0.0.255 area X

Lasty , If you wish to advertise all your connected networks then you can apply just a single network statement instead of multiple

Network 0.0.0.0 0.0.0.0. Area X

res 

Paul

[mmercaldieze]

Thanks I have to configure this on a p2p interface with redistribution so I will have to use router ospf and debating to setup ospf point to point or non broadcast

[Masoud Pourshabanian]

Hello,

Point to point and non-broadcast are two different things.

Point-to-point means no DR selection.(concerning about DR/BDR selection)

Non broadcast means your neighbor must be configured manually because OSPF is not able to find neighbors.(Concerning about finding its neighbors)

What is your interface type?

If it is a serial interface, you do not need to set any extra commands. It will be automatically point-to-point and broadcast.

Masoud

[mmercaldieze]

Ethernet

[paul driver]

Hello

Okay if you wish to have ospf P2P on a ethernet interface then specify ip ospf network point-to-point  under the inerface - otherwise it will default to ospf broadcast

res

Paul

[Masoud Pourshabanian]

Hello Paul,

"Okay if you wish to have ospf P2P on a ethernet interface then specify ip ospf network point-to-point  under the inerface - otherwise it will default to ospf broadcast"

 ip ospf network point-to-point will decrease adjacancy time; however, it will increase "Dead interval" from 40 to120 second which may cause problem in some situations. If you are setting point-to-point, you should manipulating timer based on the link quality.

http://networkengineering.stackexchange.com/questions/10219/ospf-election-with-a-30-link

Masoud

[paul driver]

Hello Masoud

Aplogies but you are incorrect in that statement -

OSPF it will not increase dead timers, They will be the same for P2P as with Broadcast - 4xhello interval = 40secs

They do however increase to120 secs only on:

  - Point-to-mulitpoint
  - Point-to-multipoint non-broadcast
  - Non-broadcast

And all these can be over wrote by an ospf interface command - ip dead-interval minimal hello-multiplier x

res
Paul

[Masoud Pourshabanian]

I used this link as my source. Please check it out. I might be wrong if the information in this website is wrong.

http://networkengineering.stackexchange.com/questions/10219/ospf-election-with-a-30-link

[paul driver]

Hello masoud

I guess this is some kind of bespoke testing  and not relates to the  default settings

I am on the understanding the default ospf hello/delay timers  is 10/40 respectively 

Various technical documentation supports this mainly CCO documentation 

res

Paul

[Masoud Pourshabanian]

Hello Paul,

The default timer of OSPF on point-to-point link is 10/40. It might be different when you set on Ethernet interface, but I am not sure. I just used that link as my source. That link might be wrong. I will try it later and share the result.

Best,

Masoud

[Masoud Pourshabanian]

Edited

It will be OSPF broadcast network . You should not be concern. Neighbors will be found automatically on broadcast networks. You do not have to do any extra configuration.

Hope it helps,

Masoud

[paul driver · Accepted solution]

Hello Masoud

It will be point-to-multipoint and broadcast. You should not be concern. It will be set automatically. You do not have to configure it.

I dont understand - what will point-to-multipoint that you dont have to configure?

res

Paul