Smoorpo
05-04-2008, 07:31 AM
Hi Todd, and all members; I've got two questions, regarding CCNA 640-802 book; Review Questions, 17 and 20. For me, there are two mistakes, here is what I mean:
20- I could not find ANY feasible answer to this; as Todd says, we know DLCI is local; but we also know that DLCI is a way to identify a circuit- and not a "signaling standard" (that would be the LMI instead!!). I believe there is a typo in answer "A", and it should have been: A- identifies the circuit between Router A and the frame switch.
Besides, willing to be very, very picky, I believe answer B can not be considered wrong; as Todd says in the chapter, the DLCI from router A, coupled with slot/port of the first switch, starts a chain of references: DLCI+SLOT/port at every switch crossed; eventually terminating on the dlci200 (on the router B side), coupled with slot/port of the closest FR switch to router B; so I say, dlci 100 INDIRECTLY means to router A, the link until router B; it's a 1-to-1 correspondence, even though not a directly explicit one.
17- Here the problem should be: there are no RIP updates ("Broadcast" statement missing); therefore, the routing table of one router is more up-to-date than the other router's; therefore A knows how to get to B, but B doesn't know how to get to A; therefore... when A sends a PING to B -remembering that PING is intrinsecally a round-trip packet: goes&comes_back- it should NOT come back!!! I don't think it's possible that Central router can ping to Remote one. It could -at most- deliver the ping packet to Remote_Router, and then it would "die" there, not having a route "back home"... am I right?
After all, the route followed by the returning ICMP packet (from Remote to Central) should be exactly the same followed by the users on Remote, attempting (and failing) to access Central Router...
Regards, and thanks for answer (whoever feels like contacting me, pls feel free) :p; my email: ihatecoldwinter@yahoo.com
Luca
20- I could not find ANY feasible answer to this; as Todd says, we know DLCI is local; but we also know that DLCI is a way to identify a circuit- and not a "signaling standard" (that would be the LMI instead!!). I believe there is a typo in answer "A", and it should have been: A- identifies the circuit between Router A and the frame switch.
Besides, willing to be very, very picky, I believe answer B can not be considered wrong; as Todd says in the chapter, the DLCI from router A, coupled with slot/port of the first switch, starts a chain of references: DLCI+SLOT/port at every switch crossed; eventually terminating on the dlci200 (on the router B side), coupled with slot/port of the closest FR switch to router B; so I say, dlci 100 INDIRECTLY means to router A, the link until router B; it's a 1-to-1 correspondence, even though not a directly explicit one.
17- Here the problem should be: there are no RIP updates ("Broadcast" statement missing); therefore, the routing table of one router is more up-to-date than the other router's; therefore A knows how to get to B, but B doesn't know how to get to A; therefore... when A sends a PING to B -remembering that PING is intrinsecally a round-trip packet: goes&comes_back- it should NOT come back!!! I don't think it's possible that Central router can ping to Remote one. It could -at most- deliver the ping packet to Remote_Router, and then it would "die" there, not having a route "back home"... am I right?
After all, the route followed by the returning ICMP packet (from Remote to Central) should be exactly the same followed by the users on Remote, attempting (and failing) to access Central Router...
Regards, and thanks for answer (whoever feels like contacting me, pls feel free) :p; my email: ihatecoldwinter@yahoo.com
Luca