ospf neighborship with secondary address

Unanswered Question
Jan 3rd, 2010

hello

diagram

R1 ----------R2

R1

int s0/1

ip add 1.1.1.1 255.255.255.0

ip add 1.1.1.5 255.255.255.0 sec

Router ospf 1

net 0.0.0.0 255.255.255.255 a 0

R2

int s0/1

ip add 1.1.1.2 255.255.255.0

ip add 1.1.1.6 255.255.255.0 sec

Router ospf 1

net 0.0.0.0 255.255.255.255 a 0

Issue faced:

neighborship building with primary address but neighborship is not building with secondary address

reference:

jeff doyle says that if secondary address is part of primary network or subnet then ospf neighborship will build.

pls suggest!!!!

I have this problem too.
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Marwan ALshawi Sun, 01/03/2010 - 22:15

do debug ip ospf adj

and see what is the issue

mainly if you have two ips as primary and secondary in two differnt subnet they must be in the same area as well to work with ospf, but both of the ips in the same subnet never tried it!!!

do you see any benefit of using this approach !!!

also one common way that you can use is sub interfaces

good luck

if helpful Rate

sourabh1000_2 Sun, 01/03/2010 - 22:23

hello,

i already checked that with different subnet but neigborship was not forming but for my practice test, i need to confirm whether we can able to form neighborship or not with secondary ip address withing the same subnet of primary subnet.

i will confirm the debug output very soon

thanks for reply

sourabh

KARUPPUCHAMY MA... Sun, 01/03/2010 - 22:57

Hi,

As per your config, the neighborship should establish,please find the attachment for you ref..

i hope some problem with your interface type config and as per theory Jef doyle it is working for me.

Karuppuchamy,CCIE(R&S),CCSP

Attachment: 
sourabh1000_2 Sun, 01/03/2010 - 23:03

hello Mr.Karuppuchamy,

as per your attachments, neighborship is forming with primary ip addresses but not able to see the neighborship with secondary ip address!!

Thanks and Regards,

sourabh

KARUPPUCHAMY MA... Sun, 01/03/2010 - 23:47

Hi,

Please find the comments from Jef Doyal "CCIE Professional Development Routing TCPIP, Volume I, Second Edition" about secondary IP address config in OSPF

Two rules are related to the use of secondary addresses in an  OSPF environment:

  • OSPF will advertise a secondary network or subnet only if it is  also running on the primary network or subnet.

  • OSPF sees secondary networks as stub networks (networks on  which there are no OSPF neighbors) and therefore will not send Hellos on them.  Consequently, no adjacencies can be established on secondary  networks.

and i have gone through jef doyle abt your comments i am not able to find out..can you tell me , where you have found that.

Thanks

Karuppuchamy CCIE(R&S),CCSP

Giuseppe Larosa Mon, 01/04/2010 - 02:02

Hello Sourabth,

Karuppuchamy's notes are correct.

it is not possible to form OSPF adjacencies using secondary IP addresses, there are conditions to have secondary IP addresses advertised if primary addresses are part of a network area command.

Only primary address is associated to a link and OSPF operates on links not IP addresses.

>> For OSPF to operate on the interface, the primary address of the interface must be covered by the network area command. If the network area command covers only the secondary address, it will not enable OSPF over that interface.

see

http://www.cisco.com/en/US/docs/ios/iproute/command/reference/irp_osp2.html#wp1013362

The scenario changes if you use RIPv2 you can be able to build a neighborship on secondary ip addresses.

Hope to help

Giuseppe

sourabh1000_2 Mon, 01/04/2010 - 06:26

hello Giuseppe,

actully i am taking meaning from below rule is that if secondary network or subnet is part of primary network or subnet then it will form a neighborship, am i right or wrong? OR it will only advertise secondary network but not to form neighborship, is this right?

means is OSPF, anyhow, we can not form neighborship with secondary ip address, is this right?

Two rules are related to the use of secondary addresses in an  OSPF environment:

  • OSPF will advertise a secondary network or subnet only if it is  also running on the primary network or subnet.

Thanks and Regards,

sourabh

Giuseppe Larosa Mon, 01/04/2010 - 06:52

Hello Sourabth,

>> it will only advertise secondary network but not to form neighborship, is this right?

means is OSPF, anyhow, we can not form neighborship with secondary ip address, is this right?

yes and yes

as explained in IOS command reference. The book should list the conditions under which the IP subnet of secondary address is advertised in OSPF only.

You can never expect to build on OSPF adjacency on secondary ip addresses.

Hope to help

Giuseppe

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