CCNA 2 Chapter 3 Exam Answers

Dynamic routing protocols are viewed as less secure than static routing because they commonly forward routing information on the same links that data traffic is crossing.

When a router locates a parent route that matches the destination IP address of a packet, the router will then examine the level 2 child routes contained within it.

A level 2 child route is a route that has a network with a mask that is greater than the classful equivalent. An ultimate route is a route that uses a next-hop IP address or exit interface to forward traffic.

Routers running IOS release 15 have link local routing table entries for both IPv4 and IPv6. The selection of both IPv6 routes and IPv4 routes is based on the longest matching prefix. The routing tables of both IPv6 and IPv4 use directly connected interfaces, static routes, and dynamically learned routes.

The network command is used to advertise the directly connected networks of a router. It enables RIP on the interfaces that belong to the specified network.

When Cisco Express Forwarding (CEF) is not being used on a router, a recursive lookup must be performed when a route using a next-hop IP address is selected as the best pathway to forward data.​

Dynamic routing protocols consume more router resources, are suitable for larger networks, and are more useful on networks that are growing and changing.

By default, dynamic routing protocols forward messages across a network without authenticating the receiver or originator of traffic. Static routes increase in configuration complexity as the network grows larger and are more suitable for smaller networks. Static routes also require manual intervention when a network topology changes or links become disabled.

The router learned, via RIP, that 172.16.0.0 is variably subnetted, and that there are two subnet and mask entries for that network. This means that RIP version 2 is running on both routers and that the command no auto-summary has been applied on the neighbor router. RIPv2 has an administrative distance of 120 and this router will advertise all connected networks to the neighbor via 192.168.1.1.

The RIP protocol was created with a metric that does not support larger networks. Other routing protocols, including OSPF, EIGRP, and IS-IS, scale well and accommodate growth and larger networks.

The three components of dynamic routing protocols include:
Data structures
Routing protocol messages
Algorithm

An ultimate route is a routing table entry that contains either a next-hop IP address (another path) or an exit interface, or both. This means that directly connected and link-local routes are ultimate routes. A default route is a level 1 ultimate route, but not all ultimate routes are default routes. Routing table entries that are subnetted are level 1 parent routes but do not meet either of the two requirements to be ultimate routes. Ultimate routes do not have to be classful network entries.

Even though OSPF has a higher administrative distance value (less trustworthy), the best match is the route in the routing table that has the most number of far left matching bits.

The destination IP address 172.16.0.66 belongs to the network 172.16.0.64/26. In the routing table there is a route learned by EIGRP (identified with code “D”) with 192.168.1.6 as the next-hop address and Serial 0/0/1 as the exiting interface.

Routes in a routing table are manually created or dynamically learned. Letter D indicates that the route was learned dynamically through the EIGRP routing protocol.

BGP is a protocol developed to interconnect different levels of ISPs as well as ISPs and some of their larger private clients.

Before the administrative distance of a route is compared, the route with the most specific best match is utilized. The 192.168.14.0/26 network contains the best match to the destination IP address of 192.168.14.20 and thus the 192.168.14.0/26 RIP route is utilized over the EIGRP and OSFP routes, regardless of administrative distance.

Directly connected networks are identified with a C and are automatically created whenever an interface is configured with an IP address and activated.

The default-information originate command instructs a router to propagate the static default route in RIP or OSPF.

The command being entered by the engineer will cause RIPv2 to activate on the interface for the 192.168.10.0 network. If RIPv1 is configured, the router will send only version 1 updates, but will listen for both version 1 and version 2 updates. If RIPv2 is configured, the router will send and listen to only version 2 updates.