3Com CoreBuilder 7000 Operation Manual page 70

70 C 4: P
HAPTER RIVATE
N - -N I
ETWORK TO ETWORK NTERFACE
A
X
C
E
Figure 15 Looping in e-IISP
This figure shows a sample network topology, in which the signal is sent
as follows:


Switch E is transmitting to Switch A.


The signal is sent from E to C (see number 1 in Figure 15).


The link from switch C to A goes down (as indicated by an "X").


Switch C knows that the link is down. It cannot send the message
back to Switch E, so it sends the signal to Switch D (see number 2).
(PNNI) V 1.0
ERSION
B
D
2
4
F
Destination
Source