Microsoft Word – quiz6.docx
CMPT 471 Quiz 6 solution
1) [9 points] Consider the routing table from host A shown below.
Entry number
(for reference)
network gateway Netmask Interface
1 196.168.1.0 196.168.0.2 255.255.255.128 eth1
2 196.168.0.0 * 255.255.255.0 eth1
3 172.17.0.0 172.32.0.3 255.255.0.0 eth2
4 172.18.0.0 * 255.255.0.0 eth3
5 172.32.0.0 * 255.248.0.0 eth2
Consider packets with destination addresses 172.17.55.92, 172.51.1.253 and 196.168.1.132.
For each address indicate which row in the routing table is used to forward the packet,
which interface the packet will be forwarded through, and the IP address of the host the
packet will be sent to in the Ethernet layer.
172.17.55.92 line 3 eth2 172.32.0.3
172.51.1.253 No line
matches
The packet will be
dropped
Because there is not default in
the routing table
196.168.1.132 no line
matches –
the packet will be
dropped
because there is no default entry
in the routing table
(1 point for each for each of the items shown in blue in the table above)
2) [4 points] Is RIP a link-state or distance vector type protocol?
Consider triggered updates within the RIP protocol. Explain how triggered updates
are used to mitigate slow convergence.
RIP is a distance vector protocol (1 point)
RIP uses triggered updates to help increase the speed of convergence. When an
updated routing table is calculated, and the calculation results in changes in the
distance vector (1 point), this will cause RIP to send a ‘triggered update (1 point)
A normal update will wait until the T seconds between successive transmissions of
updates has expired. A triggered update is sent almost immediately. (1 point)
It does not wait for the next periodic update an additional ‘triggered’ update is sent to
increase the speed that the update travels through the network.
3) Consider an AS which is running OSPF as its internal routing protocol.
a. Based on the the AS illustrated below the following questions
(-½ point each for each missing or extra router, maximum deduction n
umber of points for each part)
i. (2 point) Which routers are area border routers
R1, R4, R6, R7
ii. (1 point) Which routers are border routers
R0, R9
iii. (2 points) Which routers are part of the backbone area
R0, R1, R2, R3, R4, R6, R7, R9
iv. (2 point) Which networks are stub networks
N6, N3, N4, N8
4) [2 points] Which protocol is used to keep track of which hosts on a network are
members of which multicast group In IPv6? in IPv4?
IPv6 MLD (1 point)
IPv4 IGMP (1 point)
5) [3 points] Which multicast routing protocol is running in the virtual lab?
PIM-S (1 point)
Is RIP running in the virtual lab?
NO (1 point)
Is static routing being used for unicast routing in the virtual lab?
YES (1 point