Does floating static route really goes with dynamic routing?

[MikeNY85]

Hello professionals,

My question is "why would we configure a floating static route, if we already using a dynamic routing protocol in the network"?. isn't the dynamic routing protocol has the capability to calculate an alternate path in case of link failure?. Of course, a floating static route works best with static routing.. I am just not convinced with the fact that floating static route works also with dynamic routing.

Any help would be much appreciated..

Thanks in advance!

[MHM Cisco World · Accepted solution]

you have Edge router and dual ISP 
and you need routing 
you can not run routing because not always the ISP side accept run routing with costumer 
so the solution is Static route 
and if you have dual ISP link then you need floating static route for failover.

so you run routing protocol inside your network and config static between your edge router and ISP. 

[MikeNY85]

@MHM Cisco World I really appreciate your help a lot and thanks very very very much for your response. It's always good to learn from real world examples and professionals like you!.

[MHM Cisco World]

You are so so welcome 

[balaji.bandi]

"why would we configure a floating static route, if we already using a dynamic routing protocol in the network"?  - Sure its all depends how you configured and use case.

if this not so big network and not many routers in place , simple static  routing works.

[David Ruess · Accepted solution]

Hello,

With your specific question a scenario could be you lose your OSPF/EIGRP neighborship (for any of 1000 reasons) but still maintain connectivity. Your floating static route (usually default route) will kick in and at least forward most of your traffic out of your network, or wherever your floating static route points.

Is it likely to happen especially with redundancy, probably not. But its also not hurting anything or really taking up resources as it wont be in use unless that scenario happened.

Reasons you can lose neigborship:

-Key rotation (authentication) misconfigured or not enough overlap

-Misconfiguration change on ISP side

-Change in routing table (network/router churn)

-Jr engineer not fully understanding some configurations (personal experience)

And many more.

-David

[MikeNY85]

@David Ruess thanks very much David for you answer and I really appreciate it.

[Joseph W. Doherty]

Possibly the most likely situation where you might see both dynamic routing and static routing especially with a floating static is a case like @MHM Cisco World described.

Basically any case where the "other side" will not or can not do dynamic routing with you.