Hi Rahul,
Sorry for my lack of understanding , but is there an option for eigrp to show the next hop as 10.138.128.2 rather than the same next hop ?
EIGRP, like all internal gateway protocols (RIP, OSPF, IS-IS), constructs routing tables using the immediate next hop, unlike BGP in which the next hop is usually a far-end IP address requiring recursive routing lookup. This is the basic principle of all internal routing protocols - the next hops are the immediate neighboring routers, not far-away devices. While there is an option of having EIGRP router A tell router B that the next hop toward a particular network is router C, but even in this case, all routers A, B, and C must be in the same IP network and thus connected on a common network segment.
So, no, in EIGRP, the next hops will always be indicated as the immediate neighbors of your router. The same goes for OSFP, RIP, and IS-IS.
And are there any disadvantages of disabling the Split horizon rule ?
Split Horizon rule was invented to prevent routing loops from occurring. In EIGRP, there are additional checks performed to make sure that a routing loop never occurs, so the loop prevention provided by the Split Horizon is not really useful. However, even so, the Split Horizon helps you optimize the set of routes maintained in EIGRP topology tables. Without Split Horizon, EIGRP topology tables will hold all routes advertised by all neighbors, even by those whose path leads back to us. These entries are not harmful to EIGRP but they are useless, occupy extra memory and require processing whose effort is ultimately wasted. When running EIGRP on Non Broadcast Multi Access (NBMA) networks such as Frame Relay or DMVPN where only a subset of routers has direct visibility to each other, deactivating Split Horizon is often required. However, on all other network types, deactivating Split Horizon is not outspokenly harmful but at the same time, it provides no benefits worth the added effort.
Best regards,
Peter
