OSPF reference bandwidth

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Joined: Tue Oct 08, 2019 11:52 am

OSPF reference bandwidth

Post by Felix » Tue Oct 15, 2019 2:11 pm

Hi all,

In a large network with core routers, aggregation and access routers, where is the best place to start deploying the OSPF reference bandwidth?
Core routers - uplink and downlink interfaces are 10G
Aggregation router - uplink int are 10G downlink int 1G
Access routers - uplink & downlink int 1G

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Joined: Thu Oct 03, 2019 12:47 pm

Re: OSPF reference bandwidth

Post by cstizza » Tue Oct 15, 2019 3:49 pm

Hello Felix,

“Best“ is really dependent on the desired end state here. Also without more information about the topology such as area boundaries, summarization etc. it’s really hard to understand or evaluate the impact of a given configuration change.

However having said that, I’m going to take a stab at answering your question anyway.

You need to avoid any situation where a one gig link could potentially become transit and thus oversaturated by an artificially low metric.

This could be avoided by temporarily changing the cost manually on those links before changing the reference bandwidth.

Can you share a network topology diagram that labels the link speed and also the area boundaries?

Take care,


PS - you’re illustrating why the hierarchal design of OSPF is useful!

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