Split Horizon and Enhanced IGRP
Recall that a split horizon occurs when a router will not advertise a route on the same interface from which it learned the route. In Figure 8-16, router D1 will advertise network 10.1.4.0 to D2 on serial 2/1, but D1 will not send it back to D4 on serial 2/0 because D1 learned this route from D4 on serial 2/0.
Figure 8-16 shows that the D1 router does not readvertise the route to itself, which assists in preventing routing loops.
Figure 8-16. Split Horizon
By default, split horizon is enabled on all LAN and point-to-point interfaces, but it is disabled on all NBMA networks for all distance-vector protocols, ...
Get Large-Scale IP Network Solutions (CCIE Professional Development) now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.
