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Answers to Review Questions
Answers to Review Questions
A, C. Link-state routing protocols use the Hello protocol to establish
adjacencies, and they send updates only when there is a change in the
network topology.
B. BGP is a complex external routing protocol used to advertise and
distribute available networks and paths to those
A. RFC 1930 is the RFC that defines an AS.
C. An IGP is an interior routing protocol that is used to determine the
network topology inside of an AS. RIP, OSPF, and IGRP are all inte-
rior routing protocols. IPv4 is a Layer 3 routed protocol, not a routing
C. Exterior BGP (eBGP) runs outside of an AS to distribute routing
information and AS policies. Interior BGP (iBGP) runs inside the
AS and uses its own route map separate from that used by the IGPs.
B. Interior routing protocols operate at Layer 3 of the OSI Reference
Model, which is called the Network layer.
C. A transit AS is an AS through which data from one AS must travel
to get to another AS.
D. Port 179 is used by BGP to establish a session with another BGP
peer. Ports 20 and 21 are used by FTP, and port 23 is used by Telnet.
B, C. Either a KEEPALIVE message type or an UPDATE message
must be sent in order to keep a session open during the configured
hold time. The Hold Time option can be set to zero in order to disable
it. If it is not disabled, then it can be set to no less than three seconds.
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