Chapter 5

A1: The new access list causes two hops to be added to every route except 10.33.32.0.
A2: RTB interprets all subnets of 172.16.0.0 according to its misconfigured masks. The consequences, as exhibited in each of the four entries in its route table, are

  • Entry 1: This entry is correct because 172.16.24.0 can be masked with either 22 bits or 23 bits.

  • Entry 2: Subnet 172.16.26.0 is advertised by RTC. Because the 23rd bit of this address is one and RTB is using a 22-bit mask, from RTB's perspective this one appears in the host address space. Therefore, RTB interprets the advertisement of 172.16.26.0 as a host route and marks it with a 32-bit mask in the route table.

  • Entry 3: RTB interprets its interface address 172.16.22.5 as being a member ...

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