Implementing IPv4

Question 1

What are the differences between Routing Protocol and Routed Protocol?

Answer 1

Routing Protocol is the protocol for the purpose of learning routes. Routed protocol refer to packet structure and logical addressing.

Question 2

What is the main functions of Routing Protocol?

Answer 2

1. Learn routing information about IP subnets from other neighboring routers.
2. Advertise routing information about IP subnets to other neighboring routers
3. If more than one possible route exists to reach one subnet, pick the best route based on a metric
4. Advertising that some routes have failed and pick a new currently best rout if network topology changes.

Question 3

______ is a network under the administrative control of a single organization.

Answer 3

Autonomous System(AS)

Question 4

What is the difference between IGP and EGP?

Answer 4

Interior gateway protocol was designed for the use inside a single AS. The exterior gateway protocol was designed and intended for use between different AS.

Question 5

What is LSA and where does it reside?

Answer 5

Link-state Advertisement, it resides in LSDB (Link-state Database) which is collection of LSA known to a router.

Question 6

What are the three IGP are out there?

Answer 6

RIP-2, OSPF(Open Shortest Path First), and EIGRP(Enhanced Internal Gateway Routing Protocol).

Question 7

In what circumstances will a router re-flood its LSA?

Answer 7

when information change: link goes up or down. Also flood when LSA’s separate aging timer.

Question 8

How does an OSPF neighboring relationship developed?

Answer 8

The neighboring relationship develops when two routers are connected within a same VLAN or connected with a serial link. They each sends OSPF Hello messages to introduce themselves to the neighbor. Two must have compatible OSPF parameters.

Question 9

What is the CLI to show OSPF relationship?

Answer 9

“show ip ospf neighbors”

Question 10

How does OSPF solve the long processing time and memory use in a large area with hundreds of routers?

Answer 10

OSPF creates smaller LSDB per area.

Question 11

What is the advantage of using DHCP?

Answer 11

Using Dynamic Host Configuration Protocol enables mobility because mobile devices can move in and out by leasing IP.

Question 12

How does a DHCP client uses DORA to lease an IP address from a DHCP server?

Answer 12

Discover: DHCP client send and find a willing DHCP server. 0.0.0.0 to 255.255.255.255
Offer: DHCP server send to offer to lease IP address to client.
Request: Client ask server to lease the IPv4 listed in the Offer message. Host IP to 255.255.255.255
Acknowledgement: server assign that address and list the mask, default router, and DNS server IP address.

Question 13

In order to lease an IPv4 address from the DHCP server, the client has to send message to the local subnet without an assigned IP address?. What are the two IP address does the subnet use for this initial communication?

Answer 13

0. 0.0.0 reserved for use as a source IPv4 address for hosts that do not yet have an IP address
1. 255.255.255 reserved as a local subnet broadcast address(discover).

Question 14

When DHCP client sits in a different subnet than the DHCP server it uses “IP helper-address server_ip” CLI on its interface to transmit the broadcast through its local router. This process is called the _________.

Answer 14

DHCP Relay

Question 15

In DHCP Relay, the local router with the client is refer to as a ______.

Answer 15

relay agent

Question 16

When a relay agent sends a discover message, it will use its own address. When it received the offer from a server reside in another subnet it then _______ to its own subnet including the DHCP client.

Answer 16

Broadcast to 255.255.255.255

Question 17

How does routers use Time To Live (TTL) to avoid looping?

Answer 17

Routers use TTL to set a time value and every a router sends the packet that is looping, it reduce the value by one. When the value reaches 0 then they know the packet is just looping around. They will send a message to the sender TTL Exceed.

Question 18

How does Traceroute command uses TTL?

Answer 18

The command sets TTL to 1 so when it reaches a router, it will show the TTL Exceed mesasge. TTL is set to 2, 3, or 4 and so on to identify multiple hops.

Question 19

What are the advantages of using SSH or Telnet than ping and traceroute?

Answer 19

Engineers can use their own pc to connect to multiple devices using suspend feature to make concurrent connections.

Question 20

When transferring packet, only routers and hosts will have ________________ so they can route the packet, switches and hubs do not have to have those.

Answer 20

destination/source MAC addresses

Question 21

How can we place a valid route into the routing table of a Cisco IOS router?

Answer 21

1. Use OSPF with more than one router
2. Configure Static routes
3. Add an IP address to an up/up interface

Question 22

What is the metric of OSPF measures?

Answer 22

The sum of all bandwidth of interfaces in the path toward the destination network.

Question 23

When PC1 pings PC3 with a router and switch in between them, PC1 sends an ICMP Echo Request with destination MAC address of ______, then it will send the packet with its own MAC address as source MAC address.

Answer 23

R1