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redistribution of routes

I have a general question: Let say

r1 running ospf and rip or eigrp

r2 is running ospf connected to r1, and (subnet

r3 is running rip or eigrp connected to r1,(subnet

having said that r1 is running two protocols and if i do show ip route at this point, all I will see

directly connected routes on r1, now

I do mutual redistribution on r1, Now I should see route network on r2 as E2 route, and should also see on r3 as R or EX on r3.

My question when redistribution happened on r1, technically r1 should look for either ospf or rip/eigrp networks in its routing table to redistribute, not directly connected networks. How does it pickup the directly connected routes and redistributes in each protocol knowing that one interface is running ospf while the other one is running rip or eigrp.


Re: redistribution of routes

I think what you're saying is that you have this:

interface 1

ip address


router ospf 100

network area 0


router eigrp 100

redistribution ospf 100 metric 1000 1 255 1 1500

Or something close to that, and you want to know why the route shows up in eigrp as an external, since it's a connected route, rather than an ospf route? Because when you put the network statement in ospf, ospf takes "ownership" of the route in the routing table, so eigrp "sees" this route as an ospf route. The "ownership bits" are inclusive, rather than exclusive, so only the existence of the ospf bit is checked when redistributing into eigrp, not the lack of existance of the other bits.

I hope this makes sense.



Re: redistribution of routes

I think its because they use their databases to redistribute not the route table.

Community Member

Re: redistribution of routes

Thanks Russ! Good expalanation. That is what I was looking for. Somebody confused me by saying that when redistribution happens, router looks into the routing table and picks the routes if it sees as an ospf route or eigrp etc. When I did this in the lab I noticed that connected routes in redistrubtion router were also showing on r3 and r2. Now I know why?


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