The FD is the lowest distance a router has to a specific network. A router may have more than one path to said network, but the lowest distance is FD and it is entered into the routing table. More than one route to said network can still exist and it will be entered in the EIGRP topology table as a back-up route.
Without reading of the examples, I am guesing that a route's metric in the EIGRP topology table has changed. Even if it goes lower than it was previously, if it's not lower than the FD (the route in the routing table) than the FD to that netwtork doesn't change. If it is lower, than it will change the FD as it will become the new FD. -- RFC 1149 Compliant. Get in my head: http://sar.dynu.com ""Hamid Ali Asgari"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Hi, > > Studying EIGRP, I got to a question: When is the Feasible Distance > (FD) for a destination updated. In Jeff Doyles Routing TCP/IP, > chapter 8, it says that as a result of a local computation the > following may occur: > > -If the feasible successor with the lowest distance is different from > the existing successor, the feasible successor will become the > successor. > -If the new distance is lower than the FD, the FD will be updated. > -If the new distance is different from the existing distance, updates > will be sent to all neighbors. > > So I asume that as a result of a local computation the FD may be > updated (reduced). > > Later in this chapter, before figure 8.15 it says: Because the > distance to 10.1.7.0 has increased and the route did not become > active, the FD is unchanged at Lilienthal. > > In EIGRP's White Paper on cisco's web site, after figure 3 it says: > When the link between Routers One and Three goes down, Router One > examines each path it knows to Network A and finds that it has a > feasible successor through Router Four. Router One uses this route, > using the metric through Router Four as the new feasible distance. > > In the book , Network Design and Case Studies by Cisco , Chapter 3 > Designing Large Scale Ip netwoks, Subtitle : Enhanced EIGRP > Convergence , It is mentioned that the > FD can only change during an active-to-passive transition . > > I am totally confused about the FD and what triggers an update for > it. I don't get it. Is a ROUTE ACTIVATION required for a FD update > necessarily? > > If the router receives a better advertisement , and if the FD is > lower , I feel FD can change during a local computation itself . > > Could any one explain? > > Thanks in advance, > > Hamid > > __________________________________________________ > Do You Yahoo!? > Yahoo! Greetings - send holiday greetings for Easter, Passover > http://greetings.yahoo.com/ Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=39954&t=39954 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
