Is EIGRP a layer3 or Layer? does it sit on top of IP layer?

[saishreevj]

Is EIGRP a Layer3 or Layer4 ? Does it sit on top of IP Layer?

[Giuseppe Larosa · Accepted solution]

Hello @saishreevj ,

EIGRP uses IP protocol type 88. OSPF uses IP protocol type 89. RIP uses an UDP port.  BGP uses TCP port 179.

From an encapsulation point of view, or what we can see in a packet capture, EIGRP is at level 4 over IP like TCP and UDP.

If we look at what EIGRP does :  it is a routing protocol of type IGP  that can be used to provide dynamic routing services to the routed protocol IP, all this happens at Layer 3.

Hope to help

Giuseppe

[saishreevj]

@Giuseppe Larosa Thanks for the explanation. 

[Joseph W. Doherty]

Assuming you're referring to the OSI model, I recall (?) reading in the actual OSI documentation, the 7 layer model actually defines routing protocols "outside" it.

Personally, I often consider routing protocols a layer 7 application, which just happens to "adjust" (L3) routing information.

BTW, if both approaches seem odd, what layer is manual static routing?