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arkala anudeep
Beginner

EIGRP summary route AD

Have read this many times, that EIGRP summary route has an AD value of 5 by default,

https://networklessons.com/ip-routing/how-to-configure-administrative-distance/

but in which scenario, do we see it? I have a DMVPN hub-spoke setup, i'm trying to summarize  a default route from HUB, it does send the summarized route, but with an AD value 90, i would like to know, a scenario where we see AD as 5.

Thanks in advance

2 REPLIES 2
Jon Marshall
VIP Community Legend

The AD of 5 is only on the router advertising the summary address.

Any router receiving the summary route advertisement will have an AD of 90 because AD is not passed in routing updates.

The reason for creating an AD of 5 on the local router is to avoid a routing loop ie. it is given a lower AD than EIGRP internal or external so if the router does not have a more specific route the packet is not forwarded.

Jon

Agreed Jon, but here is the ouput:

====

R1(config-if)#do show run int tun 0
Building configuration...

Current configuration : 333 bytes
!
interface Tunnel0
ip address 10.1.0.1 255.255.255.0
no ip redirects
ip nhrp authentication DMVPN
ip nhrp map multicast dynamic
ip nhrp network-id 1
ip nhrp redirect
ip summary-address eigrp 1 10.0.0.0 255.0.0.0

===============

On R1:

10.0.0.0/8 is variably subnetted, 17 subnets, 3 masks
D 10.0.0.0/8 is a summary, 00:04:29, Null0
D 10.1.68.0/24 [90/26880512] via 10.1.0.5, 00:04:28, Tunnel0
D 10.1.221.0/24
[90/3072] via 10.1.12.2, 00:06:03, GigabitEthernet0/0.12
D 10.1.222.0/24
[90/3072] via 10.1.12.2, 00:06:06, GigabitEthernet0/0.12
D 10.1.239.0/24 [90/26880256] via 10.1.0.9, 00:04:28, Tunnel0

---------------

Output from a neighbor, which got the summary route but the AD is 90:

2.0.0.0/32 is subnetted, 1 subnets
D EX 2.2.2.2 [170/27008256] via 10.1.0.1, 00:06:03, Tunnel0
10.0.0.0/8 is variably subnetted, 8 subnets, 3 masks
D 10.0.0.0/8 [90/26880256] via 10.1.0.1, 00:05:30, Tunnel0

am i missing something here?