Can anyone tell me why we use a metric when re distributing a protocol into another, say i want to re distribute my eigrp routes into rip, why would a specify a metric in this ? can anyone give me a good example as im stuck on this ?
Any routing protocol have their own way of calculating its metric to reach a destination.
Rip uses hop count
EIGRP uses metric (bandwidth,delay,load,mtu,reliability)
OSPF uses cost
So when you redistribute one routing protocol like rip into another routing protocol like eigrp u have to tell rip to start using metrics in the way eigrp calculates.
I hope this will clear the use of metric in redistribution in a very simple terms.
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Please go through the link below and it will help you:
Lets me try to put in simple terms. Any routing protocol have their own way to calculate which is the best path.
For suppose from a particular source to reach a particular destination there are 2 paths so a routing protocol check which is the best path and to know which is the best path every protocol has its own way.
How RIP will decide which is the best path---it will check how many hops he has to take if he take first path and how many hops it has to take if he chooses second path so the path with minimum hops will be chooses by RIP.
How EIGRP will decide which is the best path---it will calculate the metric using formula (lets not go deep into the formula) it will take into consideration bandwidth , delay by default and calculate the best path and once best path is chooses it will take that into consideration.
Now if you want RIP to be distributed into EIGRP , RIP has to follow the way how EIGRP calculate the best path not its own way. It is same as if you come and stay in your friends house you have to follow some regulation the way your friend stay in his house and not the way you follow in your house.
Same way when RIP is going into the domain where EIGRP is running RIP has to follow the way EIGRP calculates it metric and that is the reason when doing redistribution into any protocol we have to tell the redistributed protocol which is RIP here to follow the way EIGRP is calculating its metric and that is teh reason we use metric command in redistribution.
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To explain this, let us take an example.
You are working with Company A, which has certain policies. There is another company B with come policies as well. Let us say that you have accepted a consultancy job with company B and you are serving both A and B companies.
Now when you will go to company B you have to work according to the policies defined there and you will follow the plocies when you are in company A.
Now company A is RIP with policy (metric = hopcount ) and company B is EIGRP with policy (metric = composite metric ). Now when you want to advertise some RIP routes into EIGRP domain, you have to set the Metric so that they get advertised in the EIGRP domain and vice versa in case of EIGRP routes advertised in RIP domain..
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I read your reply but which best ?
like if I have EIGRP and OSPF then I redistribute in EIGRP or OSPF or in both .
Hi Amit, thanks for the response, I kind of get you but what values do the metrics correspond to, for example my router has eigrp and rip, with have re distributed rip into eigrp, by doing redistribute router rip metric 5, what exactly is the value of 5 saying, eigrp has 5 metrics, is it saying use 5 metrics the same as eigrp ?, can you give me an example ?
thanks a million
Lets me try to clear once again and see if this makes you easy.
First can you confim if you are redistributing RIP into EIGRP or EIGRP into RIP.
As you said you have re-distributed rip into eigrp and you have used a command redistribute router rip metric 5 that is wrong.
You are taking rip into eigrp then you have ask rip to follow the policies followed by eigrp.
It will be something like this
router eigrp 100
redistribute rip metric 100 100 200 1 1500
this will tell rip to start using metric bandwidth ,delay,load,reliability and mtu for calculating the best path when it gies into eigrp domain instead of using hops count which rip uses in general.
Now if you waaan a redistribute eigrp into rip
redistribute eigrp 100 metric 4
now what this will do is tell eigrp to start using metric hop count instead of composite metric to clculate best path when it goes into rip domain.
I hope this will clear everything to you.
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Hi Ankur, thanks for the great reply, Ive taken a look and im redistributing eigrp into rip
, my question still is, what does the metric 4 actually mean ? on mine is says 5 ? what does it go up to and why have you used 4 ?
Metric 4 means hop count 4 (4 routers to be crossed). I just used 4 as an example.
When you redistribute eigrp into rip you say that all the routes which are getting into rip domain now will get a hop count of 4 which means to reach a destination learned via eigrp into rip domain , rip router has to go via 4 routers.
As you have given 5 it is hop count 5 ( 5 routers to be crossed). It all depends upon network admin how he play with the metric values and what metric value he want to asign to redistributed routes and it should be done very carefully.
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So with Rip, I would bascially look at how many routers are in my network here that all run rip, and then say the furthest away was 10 hops, I would just put a metric of 10 in ?