Suppose P, Q, and R are network service providers, with respective CIDR address allocations (using the notation of Exercise 45) C1.0.0.0/8, C2.0.0.0/8, and C3.0.0.0/8. Each provider's customers initially receive address allocations that are a subset of the provider's. P has the following customers:
PA, with allocation C1.A3.0.0/16, and
PB, with allocation C1.B0.0.0/12.
Q has the following customers:
QA, with allocation C2.0A.10.0/20, and
QB, with allocation C2.0B.0.0/16.
Assume there are no other providers or customers.
(a) Give routing tables for P, Q, and R, assuming each provider connects to both of the others.
(b) Now assume P is connected to Q and Q is connected to R, but P and R are not directly connected. Give tables for P and R.
(c) Suppose customer PA acquires a direct link to Q, and QA acquires a direct link to P, in addition to existing links. Give tables for P and Q, ignoring R.
Exercise 45
Table 4.16 is a routing table using CIDR. Address bytes are in hexadecimal. The notation "/12" in C4.50.0.0/12 denotes a net mask with 12 leading 1 bits, that is, FF.F0.0.0. Note that the last three entries cover every address and thus serve in lieu of a default route. State to what next hop the following will be delivered.
(a) C4.5E.13.87
(b) C4.5E.22.09
(c) C3.41.80.02
(d) 5E.43.91.12
(e) C4.6D.31.2E
(f) C4.6B.31.2E
