Understanding Network Topology and Routing Protocols

SIT202: COMPUTER NETWORKS TRISEMISTER 2, 2018
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Course Unit

QUESTION 1:
On this sample topology there are 6 hosts each having a unique ip address, 2 switches and a
router that connects to the internet then to the remote server. To demonstrate how both switches
and routers cross this network will look at the table which they maintain. ARP Table mapping of
ip address to Mac address, Mac Address Table which maps switches to the mac address. As
traffic goes through the switch, devices that are connected to each port by Mac Address are
identified and are recorded by the Mac Address table. Routing Table maps the ip network to
interfaces.
PC-1 has the data that needs to be conveyed across the network and to the destination that is the
remote server. It also has the ip address of the remote server so PC-1 creates an L3 header that
basically consists a few pieces of information (Doeppner, 2010). Mainly, Source ip address
(SRC) and Destination ip address that is 192.168.10.8/24 and destination ip address (DST) which
in this case is the remote server. PC-1 then compares the destination ip address on its own
network to determine that it’s a full network. PC-1 will then create a layer 2 to take the packet to
the router and since it doesn’t have the mac address it will need to use the ARP to discover its
default gateway’s Mac address. The host then sends the ARP request 192.168.10.0/24 to the
router. ARP request is a frame that literally asks if the ip address is there then sends to the mac
address. First of all the switch will basically learn the address and broadcast the ARP request to
the entire network and both the router and the Human Resource pc will receive the request and
since the Human Resource Machine doesn’t have the response to the request it will discard it.
The router on the other hand generates the response. The switch receives the response and
automatically learns the mac address of the respondent which was received on one of the port
that was connected to the router then forward the response to the host which in this case is PC-1
(Jimmei, 2008). This entire time the data is held by the host while waiting for the address
resolution to be processed to complete.
Since PC-1 has the Mac Address it can finally sends data to the remote server. The host creates
an L2 header that sends the packet. L2 is made up of the source and destination address of the
router. L3 contains Source ip address and the destination ip address of the remote server. L3’s
main work is to send data from the sender to the receiver while L2 basically gets the data from

hop to hop within the network. The frame arrives on the switch which already has the entry Mac
address table on that port. The switch then forwards the frame to the Ethernet connected to the
router. On the other end the router receives the frame then withdraws the L2. The frame consist
of the data, L3 and L2 and since L2 basically consists of hops from the PC-1 to the router, it’s
withdrawn. The router then looks at the destination which in this case is the remote server that is
connected to the internet (Kerman, 2014).
In this part the router then determines the dynamic routing protocol that is going to use to convey
the frame. Routing protocol determines the best path to each network, which is then added to the
routing table which is one of the primary table. This trade enables switches to consequently find
out about new systems and furthermore to discover interchange ways if there is interface
inability to the present system. Contrasted with static steering, dynamic directing requires less
managerial overhead. For this situation there two kinds of dynamic steering convention that is,
Distance Vector Routing protocol and Link State Routing Protocol. Distance Vector Routing
Protocol routes are advertised as vectors of distance and direction. It is determined by the
number of hop counts and direction to the next hop router and exit interface. It basically uses a
signpost to the next router. Link-State Routing Protocol on the other hand creates a complete
view of the network by gathering information from all other routers. In contrast to distance
vector, this determines the connectivity of the network and does not utilize intermittent updates
of their routing information data to the neighbors. Since the frame needs to reach to the
destination and we basically don’t know which geographical area the server is located. The
router will be promoted to use the link state routing protocol which is determined by the strength
of the connectivity of the network.
Router will send an ARP response which will be broadcasted to request for the mac address of
the remote server (Ooka, 2013). On the other end, the request is received through the entire
network and since it is the stitch, it is connected to the remote server then it generates a response.
The router then attains the mac address and since it already has the ip address of the remote
server then the frame is received and before the withdrawal of the data, L3 is first eliminated
since it has confirmed the destination ip address. And now since it has received the data the
server has to respond to pc-1 that the data sent has been received. The whole process then is done
for the response.