EIGRP OTP Explained: Enhancing Network Efficiency and Security
EIGRP OTP Introduction
We use EIGRP OTP or EIGRP Over the Top on those routers that are not directly connected. It is used in the situation when your router is connected to the ISP’s routers but you don’t want to involve the service provider’s router in your routing process. Moreover, it is also used when you don’t want to connect your sites with an MPLS VPN. You will not configure anything on the service provider’s routers, but all the configuration will be made on your routers.
EIGRP OTP helps us avoid dependency on ISPs. We can only configure EIGRP OTP in the named mode. The EIGRP classic mode doesn’t support it.
OTP can work with many technologies, like
1) GRE (Generic Routing Encapsulation) Tunnels
2) DMVPN (Dynamic Multipoint Virtual Private Network)
3) IPsec (Internet Protocol SecuriEnc
4) LISP (Locator/ID Separation Protocol)
5) VTI (Virtual Tunnel Interface)
6) FlexVPN
But, here in our lab, we will use a GRE tunnel to connect two disparate EIGRP routes through the OTP process.
GRE tunnel
GRE tunnel encapsulates network layer protocols within virtual point-to-point links. It is lightweight, easy to configure, and capable of carrying multicast traffic. Traditional EIGRP requires all routers to be connected, while EIGRP OTP uses a GRE tunnel to establish neighbors across different ASes or geographical areas. The GRE tunnel will help us to complete this task.
EIGRP OTP Infrastructure
It consists of the following three main components.
1) EIGRP routers: Those EIGRP routers (routes) that you want to connect with other disparate EIGRP routers (routes).
2) GRE Tunnel: The GRE tunnel will encapsulate EIGRP packets and send them over IP internetwork.
3) Overlay Network: We configure the GRE tunnel as an overlay network over the underlying network (Public Internet, Private WAN).
Lab Topology
There are totally four routers in our lab topology, in which R1 and R4 loopback interfaces run EIGRP while all the other interfaces are advertised in RIP version 2. Our aim is to connect R1’s loopback 0 to the R4’s loopback 0 interface.
The network from R1’s fast ethernet 0/0 to R4’s loopback 0 acts as an underlay network. While the GRE tunnel will act as an overlay network.
The basic configuration of all the routers is below, one by one.
First, configure Router R1, in which we will configure its basic IP configuration, running RIP protocol, and at last, configure the named EIGRP.
Configure GRE tunnel on R1
R2 configuration
R3 Basic configuration and routing
R4 RIP and named EIGRP configuration.
Similarly, the R4 GRE tunnel configuration
Check the routing table of R1
Also, check the R4’s routing table
Similarly, check the R2 and R3 routing tables.
Similarly, also ping the GRE tunnel destination IP at R4.
Now, at the last ping, the EIGRP interface on the R4 router.
R1 has successfully ping the R4’s Fast Ethernet 0/1. From, this we can conclude that we connect two separate sites through EIGRP OTP.
