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ICND2 – IP Routing 2

October 15th, 2017 in ICND2 200-105 Go to comments

Question 1

Explanation

Host Z will use ARP to get the MAC address of the interface on R1 that connects to it and use this MAC as the destination MAC address. It use the IP address of the storage server as the destination IP address.

For example in the topology below, host A will use the MAC address of E0 interface of the router as its destination MAC address to reach the Email Server.

destination_addresses.jpg

Question 2

Explanation

Static routes remain in the routing table even if the specified gateway becomes unavailable. If the specified gateway becomes unavailable, you need to remove the static route from the routing table manually. However, static routes are removed from the routing table if the specified interface goes down, and are reinstated when the interface comes back up.

Therefore the static route will only be removed from the routing table if the S0/0 interface on RTA is shutdown.

(Reference: http://www.cisco.com/en/US/docs/security/asa/asa84/configuration/guide/route_static.html)

Question 3

Question 4

Explanation

By default a static route has the Administrative Distance (AD) of 1, which is always preferred to dynamic routing protocols. In some cases we may want to use dynamic routing protocols and set static routes as a backup route when the “dynamic” routes fail -> we can increase the AD of that static route to a higher value than the AD of the dynamic routing protocols.

Question 5

Question 6

Explanation

Discontiguous networks are networks that have subnets of a major network separated by a different major network. Below is an example of discontiguous networks where subnets 10.10.1.0/24 and 10.10.2.0/24 are separated by a 2.0.0.0/8 network.

EIGRP_discontiguous_network_1.jpg

If we configure automatic summarization at classful boundaries, users on network 10.10.1.0/24 cannot communicate with users on network 10.10.2.0/24.

If you are not clear about automatic summarization please read the last part of this tutorial: http://www.9tut.com/eigrp-routing-protocol-tutorial.

Question 7

Explanation

Link-state protocol uses hello packets to discover neighbors and establish adjacencies. After that, the routers begin sending out LSAs to every neighbor (each received LSA is copied and forwarded to every neighbor except the one that sent the LSA)

Question 8

Question 9

Explanation

Static routing can only be configured for each route manually so it is more secure than dynamic routing which only needs to declare which networks to run -> A is correct.

Also static route does not use any complex algorithm to find out the best path so no routing updates need to be sent out -> reduce routing traffic load. Static routing is useful especially in stub network links.

Note: Stub network (or stub router) is used to describe a network (or router) that does not have any information about other networks except a default route. This type of network (or router) usually has only one connection to the outside.

Question 10

Explanation

Host1 can ping the Serial interface of R2 because R1 has the network of 192.168.1.4/30 as directly connected route. But R1 does not know how to route to the network of Host2 (192.168.1.128/26) so R1 will drop that ping without trying to send it out S0/0 interface. To make the ping work, we have to configure a route pointing to that network (for example: ip route 192.168.1.128 255.255.255.192 s0/0 on R1).

Question 11

Explanation

From the CCNA ICND2 Exam book: “Routers decrement the TTL by 1 every time they forward a packet; if a router decrements the TTL to 0, it throws away the packet. This prevents packets from rotating forever.” I want to make it clear that before the router forwards a packet, the TTL is still remain the same. For example in the topology above, pings to S0/1 and S0/0 of Router 2 have the same TTL.

The picture below shows TTL values for each interface of each router and for Host B. Notice that Host A initializes ICMP packet with a TTL of 255:

TTL_ping_detail.jpg

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