
Configuring IP Services
6-8
Figure 6-3. Neighbor Reachability Exchange Begins between Two EGP
Neighbors
When Router B sends its first Hello message, Router A transitions to the UP State.
Router A responds to the Hello message with an I-H-U; however, Router B does
not yet transition to the UP state. As an active router, it must receive 3
I-H-Us within a specified time (in this case 2.5 minutes, or 5 * 30 seconds) before
transitioning to the UP state. Upon receipt of the third I-H-U within the specified
time interval, Router B transitions to the UP state (see Figure 6-4). At this point,
neighbor reachability is established.
ASN = 50 Hello = 30 Poll = 120
Mode = Passive
Router A
ASN = 51 Hello = 30
Poll = 240
Mode = Active
Router B
State = UP
State = Down
Passive Router A
transitions to the
UP state.
I-H-U
First
Hello Command
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