Seed Metrics

Cyanic

Can someone confirm this for me.

In redistribution, the seed-metric is carried over to the next hop without adding anything about the link to the next hop.

For instance:

EIGRP | OSPF
|
192.168.1.0

---

A

---

B---10---C


RouterB
router OSPF 1
redistribute EIGRP 1 subnets metric 20

Router B is performing redistribution into C. The link between B and C has a OSPF metric of 10. C would have a route to 192.168.1.0 with a metric of 20, not 30.

Cyanic

I should state that this is type 1:

redistribute EIGRP 1 subnets metric-type 1 metric 20

Undy

Metric type 1 or E1 routes will include the cost from the router to the ASBR. So the cost on router C to networks redistributed into OSPF on router B should be 30. Type E2 routes will not include the cost to the ASBR, so without the metric-type 1 it would be 20.

Cyanic

Thanks, I just got a chance to test it.

There was something I read in the BSCI SSG that made me think otherwise. Something to the effect that the sending router adds the next hop metric to the route, so the receiving router does not add it. I may be confused, but I don't have the book in front of me so I can't say what it was exactly, but I will look that section over tonight.

Cyanic

OK, I found it. This 'rule' only applies to RIP.

"The seeding router is assumed to have added 1 to the hop count."

BSCI Authorized Self Study Guide pg 392

I read a lot out of that book that day

Undy

Cyanic wrote: »

"The seeding router is assumed to have added 1 to the hop count."

I am assuming it means when you inject routes into RIP? It seems like it could make sense in some way, but I just threw it into a lab and it did not add 1 to the hop count to router C which I thought could go either way. Routers beyond C add hops which is expected. Maybe I am missing something and someone else can chime in

Cheers

Cyanic

This sounds as if this is typical RIP behavior. The sending router adds the next hop to the metric before it sends the update. I will lab this and pull a packet capture to verify.

Cyanic

Yes, RIP's behavior is to add the next hop metric to the route it is sending.