OSPF prior to backup static route

[Bruno Silva]

Hi good fellows,

I'm feeling very much problems to make a solution for my client.

The point is, i have a L3 switch with:

- one link with OSPF, and that link it's the major link.

- now, i want to install another link, for backup, and i don´t know how to make it a backup....

1. I can configure a static route but if it is available it will always choose the new link, and i want it for backup.

2. If i configure that static route with another priority, greater than OSPF, could be a possibility but OSPF will always generate the route because interface will be always on and i can´t configure SLA on it to see link availability in L3.

3.If i configure IP SLA for the static route it will be the major link, that is not also an option...

Can you give me some suggestions?

Thanks in advance!

Bruno

[Joseph W. Doherty]

If you configure a "floating static" , i.e. a static route with a higher cost than the OSPF route, if OSPF looses its neighbor adjacency, it should withdraw its OSPF route and the static should take over.

[Bruno Silva]

Hi Joseph, 

Thanks for your reply...

Yeah... I supposed that also but if I loss connection on my link which will work with ospf respectively route will disappear. 

That's not happen! If the interface is up/up the router will remain with ospf route...

Tks

[Harold Ritter]

Hi Bruno,

Why do you want to use a static route? You could establish an OSPF adjacency on the backup link, but use a higher cost on this link, so it will only be used if the primary link disappear.

Regards,

[Joseph W. Doherty]

If the interface is up/up, but OSPF loses adjacency, it should withdraw the route(s) from the neighbor.

[Harold Ritter]

Hi Joseph,

I completely agree with you. I was just pointing out that the same goal could be achieved by using ospf for both links. It's seems more simple to me to use only ospf, rather than a mix of ospf and floating static routes.

Regards,

[Bruno Silva]

Thanks a lot... 

I'll try to do that... I have to read something because I had never did that.

This network is a star topology... I've a central router and 20 sites... Each one of those sites links to a central router.

In each site I will have two link possibilities... 

Thanks once again... If I can't do this I'll back to you 

[Joseph W. Doherty]

Oh, well if the backup can use OSPF too, I too would recommend that approach.

[Bruno Silva]

Oh... "If the backup can use...", you aren't pretty sure that I can use it? Why? I'm little bit confuse.... Sorry

Rgrds

[Joseph W. Doherty]

Why use it? For the reasons Harold noted, i.e. avoiding needing to do both dynamic and static routing.

No, I'm not sure whether you can use it, as you would need to further describe your network topology.

[Richard Burts]

I agree that we need to have a better understanding of the environment to be able to provide good advice. So far I think that all we know is that there is a central router with about 20 remote sites connected in a star topology. And remote sites will have a second link. It would help if we knew what kind of link is the existing link and what kind of link will be the backup link. Also we need to know if the backup link from the remote will connect to the same central router or will it connect to something else?

Based on the little bit that we know it does seem logical that the solution might be to run OSPF on both links and to configure a higher OSPF cost on the backup link.

HTH

Rick 

[Bruno Silva]

Hi guys!

Thanks a lot for your patience...

As well as i can design, here it goes!

I've only a central router... The backbone MW (mini-link) is a private network.

I've got 20 sites like these two... one 3560 L3 switch, connected directly to backbone....

The upgrade that i want to do is install a private 4G VPN with a ISP card on isr4321.

the local lan have MW as main link and 4G as backup link...

i think that another ospf is the best idea... with this explanation, all of you keep with the same idea, no?

kind regards!

[paul driver]

Hello

Does the backup vpn links terminate on the Asa for ospf or the Central rtr?
Are all links in the same area?

Depending of the above my understanding you could utilize different dynamic options -

• interface or area default cost
• define a high max metric on the less preferred ospf rtr towards the central site
• define a non backbone area for the backup links

res
Paul

[Richard Burts]

Thanks for posting the drawing. It answers some questions and raises other questions. It seems to show a layer 2 link between 3560 switches using Alcatel. But it also shows a Cisco 7301 router and ASA5540. How do these relate. Is the OSPF connection from the remote 3560 to the main 3560, to the 7301, or to the 5540?

Also you talk about a private VPN. We do not know how that will work and whether that private VPN would support running OSPF. Can you clarify these things?

HTH

Rick

[Bruno Silva]

Hi Richard...
Yes.. it as a layer 2 link between 3560 switches and central rtr, using Alcatel....

"How do these relate. Is the OSPF connection from the remote 3560 to the main 3560, to the 7301, or to the 5540?"
-> There is no main 3560.... are all at the same level... each site as one 3560 L3 switch.

Paul ask it too... i was thinking finish the backup link at asa, but it could be better terminate it on central 7301 rtr.

The question you made for VPN it´s pertinent... i have to ask it to my collegues too. I don´t know if this vpn supports ospf. i guess so, but...

thanks!