eigrp redistribute connected

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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Comments

jjbrog

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?

burbankmarc

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.

networker050184

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.

auos

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.

networker050184

auos wrote: »

External routes are not summarized even if I turn on auto-summary.

Yes, that is correct.

auos

Many thanks to all