Chapter 32 - Implementing IPv6 Routing

Question 1

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A router has been configured with the ipv6 address 2000:1:2:3::1/64 command on its G0/1 interface as shown in the figure. The router creates a link-local address of FE80::FF:FE00:1 as well. The interface is working. Which of the following routes will the router add to its IPv6 routing table?
(Choose two answers.)

a. A route for 2000:1:2:3::/64
b. A route for FE80::FF:FE00:1/64
c. A route for 2000:1:2:3::1/128
d. A route for FE80::FF:FE00:1/128

Answer 1

A and C.

With an IPv6 address on a working interface, the router adds a connected route for the prefix (subnet) implied by the ipv6 address command. It also adds a local host route (with a /128 prefix length) based on the unicast address. The router does not add a route based on the link-local address.

Question 2

A router has been configured with the ipv6 address 3111:1:1:1::1/64 command on its G0/1 interface and ipv6 address 3222:2:2:2::1/64 on its G0/2 interface. Both interfaces are working. Which of the following routes would you expect to see in the output of the show ip route connected command?
(Choose two answers.)

a. A route for 3111:1:1:1::/64
b. A route for 3111:1:1:1::1/64
c. A route for 3222:2:2:2::/64
d. A route for 3222:2:2:2::2/128

Answer 2

A and C.

The two correct answers show the correct subnet ID (prefix) and prefix length for the two connected subnets: 3111:1:1:1::/64 and 3222:2:2:2::/64. The answer with the /128 prefix length is shown in a local route, but those routes are not displayed by the show ipv6 route connected command. The other incorrect answer lists the entire IPv6 address with a /64 prefix length, and the entire address would not be displayed as a prefix when using a /64 prefix.

Question 3

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An engineer needs to add a static IPv6 route for prefix 2000:1:2:3::/64 to Router R5’s configuration, in the figure shown with question 1. Which of the following answers shows a valid static IPv6 route for that subnet, on Router R5?

a. ipv6 route 2000:1:2:3::/64 S0/1/1
b. ipv6 route 2000:1:2:3::/64 S0/1/0
c. ip route 2000:1:2:3::/64 S0/1/1
d. ip route 2000:1:2:3::/64 S0/1/0

Answer 3

A.

All four answers show examples of commands that use an outgoing interface. The two commands that begin with ip route define only IPv4 routes; the commands would be rejected because of the IPv6 prefixes listed in the commands. The two commands that begin with ipv6 route are syntactically correct, but the command should list the local router’s interface (an interface on the router on which the command is being configured). R5 needs to use its local S0/1/1 interface as the outgoing interface.

Question 4

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https://i.postimg.cc/mD2NtTPv/Ch32-1-3-4.png

An engineer needs to add a static IPv6 route for prefix 2000:1:2:3::/64 to Router R5 in the figure shown with question 1. Which of the following answers shows a valid static IPv6 route for that subnet on Router R5?

a. ipv6 route 2000:1:2:3::/64 2000:1:2:56::5
b. ipv6 route 2000:1:2:3::/64 2000:1:2:56::6
c. ipv6 route 2000:1:2:3::/64 FE80::FF:FE00:5
d. ipv6 route 2000:1:2:3::/64 FE80::FF:FE00:6

Answer 4

B.

All four answers show examples of commands that use a next-hop router IPv6 address. Two of the answers list R5’s own IPv6 address (unicast or link-local), which is incorrect; the answer should be an address on the neighboring router, R6 in this case. For the two answers that list addresses on Router R6, the one that lists R6’s global unicast address is correct. The one that lists R6’s link-local address would also require R5’s outgoing interface, so the answer that lists FE80::FF:FE00:6 would be rejected as well.

Question 5

An engineer types the command ipv6 route 2001:DB8:8:8::/64 2001:DB8:9:9::9 129 in configuration mode of Router R1 and presses Enter. Later, a show ipv6 route command does not list any route for subnet 2001:DB8:8:8::/64. Which of the following could have caused the route to not be in the IPv6 routing table?

a. The command should be using a next-hop link-local address instead of a global unicast.
b. The command is missing an outgoing interface parameter, so IOS rejected the ipv6 route command.
c. The router has no routes that match 2001:DB8:9:9::9.
d. A route for 2001:DB8:8:8::/64 with administrative distance 110 already exists.

Answer 5

C.

IOS will add a new static route to the IPv6 routing table if, when using a next-hop global unicast address, the router has a working route to reach that next-hop address and there is no better (lower administrative distance) route for the exact same subnet. So, the correct answer identifies one reason why the route would not appear. The answer that mentions a better route with administrative distance of 110 is a valid reason for the static route to not appear, but the question states that no route for the subnet appears in the routing table, so clearly that competing route does not exist.

The other two answers are incorrect about the ipv6 route command. This command can use a link-local next-hop address but does not have to do so. Also, when using a global unicast address as next-hop, the command does not also require an outgoing interface parameter.

Question 6

The command output shows two routes from the longer output of the show ipv6 route command. Which answers are true about the output?
(Choose two answers.)

R1# show ipv6 route static
! Legend omitted for brevity
S      2001:DB8:2:2::/64 [1/0]
            via 2001:DB8:4:4::4
S      ::/0 [1/0]
            via Serial0/0/1, directly connected

a. The route to ::/0 is added because of an ipv6 route global command.
b. The administrative distance of the route to 2001:DB8:2:2::/64 is 1.
c. The route to ::/0 is added because of an ipv6 address interface subcommand.
d. The route to 2001:DB8:2:2::/64 is added because of an IPv6 routing protocol.

Answer 6

A and B.

The output shows two static routes, as noted with the “S” code on the far left. Both were added to the IPv6 routing table because of ipv6 route commands. Both have an administrative distance of 1, which is listed as the first number in brackets.

For the two incorrect answers, note that the ipv6 address interface subcommand does cause IOS to add connected IPv6 routes to the routing table, and the phrase “directly connected” with one route might make you think this is a connected route, but the “S” in the far left identifies the source of the route. Likewise, the answer that mentions an IPv6 routing protocol is incorrect because both routes have a code of S, meaning static.