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eigrp redistribute connected

auosauos Member Posts: 186
in CCNP
Hi,
I am so confused about (eigrp redistribute connected), I have below network

R1 (s1/0)<
>(s0/0) R2

And I configure R1 as below

!
interface Loopback0
ip address 10.10.10.1 255.255.255.0
!
interface Serial1/0
ip address 172.16.1.1 255.255.255.0
clock rate 64000

router eigrp 100
redistribute connected
network 172.16.0.0
auto-summary


And R2 as below

interface Serial0/0
ip address 172.16.1.2 255.255.255.0
!
router eigrp 100
network 172.16.0.0
auto-summary

It is very simple, but when I display the routing table for R2 (show ip route) it is mentioned the network (10.0.0.0) as /24 not as /8, why.

R2 routing table

172.16.0.0/24 is subnetted, 1 subnets
C 172.16.1.0 is directly connected, Serial0/0
10.0.0.0/24 is subnetted, 1 subnets
D EX 10.10.10.0 [170/2297856] via 172.29.1.1, 00:15:05, Serial0/0


R1 routing table

172.16.0.0/24 is subnetted, 1 subnets
C 172.16.1.0 is directly connected, Serial1/0
10.0.0.0/24 is subnetted, 1 subnets
C 10.10.10.0 is directly connected, Loopback0
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    jjbrogjjbrog Member Posts: 149
    I'm still working on CCNA stuff(this being NP forum, seen the post on front page) but I'd imagine its cause you have the address configured as a /24 on the loopback interface?
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    burbankmarcburbankmarc Member Posts: 460
    It's because it's an external route. You're assuming since the autosummarization is enabled, and that it's the classful edge that it should be advertised as 10.0.0.0/8, right?

    Well EIGRP summary routes are trusted and have an AD of 5, external routes have an AD of 170, so external routes are not summarized.

    I'm pretty sure that's why, I'm too lazy to look it up.
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    networker050184networker050184 Mod Posts: 11,962 Mod
    burbankmarc wrote: »
    It's because it's an external route. You're assuming since the autosummarization is enabled, and that it's the classful edge that it should be advertised as 10.0.0.0/8, right?

    Well EIGRP summary routes are trusted and have an AD of 5, external routes have an AD of 170, so external routes are not summarized.

    I'm pretty sure that's why, I'm too lazy to look it up.


    Yep thats it.

    If you use a network statement there instead of the redistribute command you will see your /8 like you are looking for.
    An expert is a man who has made all the mistakes which can be made.
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    auosauos Member Posts: 186
    burbankmarc wrote: »
    Well EIGRP summary routes are trusted and have an AD of 5, external routes have an AD of 170, so external routes are not summarized.

    External routes are not summarized even if I turn on auto-summary.
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    networker050184networker050184 Mod Posts: 11,962 Mod
    auos wrote: »
    External routes are not summarized even if I turn on auto-summary.

    Yes, that is correct.
    An expert is a man who has made all the mistakes which can be made.
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    auosauos Member Posts: 186
    Many thanks to all
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