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Using VRF-Lite, EIGRP, and Static Routes

Alexandre Vasseur
Level 1
Level 1

‎02-22-2012 02:38 AM - edited ‎03-07-2019 05:05 AM

Hi all,

I wasn't able to find any answer to my question, so i hope you can help me.

My question is :

Why we always need to define metric when redistributing static routes with VRF-Lite ?

The only information i found is : "Only connected routes can be redistributed without a default metric. The metric of redistributed connected routes is set to 0."

I will appreciate if you have anymore explanations.

Thanks for all.

Best regards,

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Peter Paluch
Cisco Employee
Cisco Employee

‎02-22-2012 03:03 AM

Alexandre,

I do not believe that the requirement for specifying the so-called seed metric is specific for VRF-lite. The following rules apply for all redistributions, both within the global routing table and within VRFs:

  • Directly connected routes can always be redistributed into routing protocols without specifying any seed metric. The routing protocol will use the metric of the interface as the seed metric.
  • Static routes can always be redistributed into routing protocols without specifying any seed metric. The routing protocol will use the metric of the resultant egress interface towards the next hop as the seed metric.
  • Redistributing routes from other IGP routing protocols into a distance-vector routing protocol in particular (i.e. EIGRP, RIP) always requires specifying a seed metric. Otherwise, the distance-vector routing protocol will use the maximum metric as the seed metric and will not advertise the redistributed routes (or it will advertise them as unreachable which is the meaning of the maximum seed metric).
  • Redistributing routes from other IGP routing protocols into a link-state routing protocol in particular (i.e. OSPF, IS-IS) does not require specifying a seed metric. Without specifying seed metric, OSPF will use the default seed metric of 20, and IS-IS will always use the seed metric of 0.

A couple of other rules govern the redistribution that involves BGP either as a source or destination routing protocol, but in order to keep things simple, I am not going to discuss these rules here.

Best regards,

Peter

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