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EIGRP neighbors

Is it possible to configure eigrp neighbor list with neighbor's loopback interface?

1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Silver

Re: EIGRP neighbors

Hello Fuad,

the answer is no because to build EIGRP adjacency you need to use physical interfaces to communicate with somebody else and the two devices have to share a common IP subnet.

on a multilayer switch you could use an SVI ip address as neighbor but there is a L2 link between the two devices

even if you use overlapping ip addresses

r1

int loop1

ip address 10.10.1.1 255.255.255.0

r2

int loop 2

ip address 10.10.1.2 255.255.255.0

the two ip addresses cannot communicate for each router other router's ip address is out its loopback and this defeats a successful communication between them.

if you use /32 ip addresses then the hellos should go trough another L3 link but:

they have TTL 1

The only exception is if there is a physical link and the interface has ip unnumbered loop1 this could be used

Hope to help

Giuseppe

2 REPLIES
Hall of Fame Super Silver

Re: EIGRP neighbors

Hello Fuad,

the answer is no because to build EIGRP adjacency you need to use physical interfaces to communicate with somebody else and the two devices have to share a common IP subnet.

on a multilayer switch you could use an SVI ip address as neighbor but there is a L2 link between the two devices

even if you use overlapping ip addresses

r1

int loop1

ip address 10.10.1.1 255.255.255.0

r2

int loop 2

ip address 10.10.1.2 255.255.255.0

the two ip addresses cannot communicate for each router other router's ip address is out its loopback and this defeats a successful communication between them.

if you use /32 ip addresses then the hellos should go trough another L3 link but:

they have TTL 1

The only exception is if there is a physical link and the interface has ip unnumbered loop1 this could be used

Hope to help

Giuseppe

New Member

Re: EIGRP neighbors

Thank you!

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