Computer Networks Cs 6250 test baNk –
100% aCCurate QuestioNs & aNswers
guaraNteed a
◉ BGP Paper:
Local Preference. Answer: Influences which BGP route will be chosen for each
destination prefix.
Done by adding / deleting / modifying route attributes in BGP advertiesments.
◉ BGP Paper:
Locally-Controlled Attributes for BGP Decision Process (2). Answer: 1. Local
preference
2. Lowest IGP cost to border router
◉ BGP Paper:
Neighbor-Controlled Attributes for BGP Decision Process (2). Answer: 1. AS
path length
2. MED
,◉ BGP Paper:
Filtering. Answer: Eliminates certain routes from consideration and controls
who they will be exported to.
May be applied before preference (inbound filtering) and/or after preference
(outbound filtering).
Done by instructing routers to ignore advertisements with attributes matching
certain values or ranges.
◉ BGP Paper:
Tagging. Answer: Allows an operator to associate additional state with a route,
which can be used to coordinate decisions made by a group of routers in an
AS, or to share context across AS boundaries.
The key mechanism is the community attribute.
◉ BGP Paper:
Community Attribute. Answer: A variable-length string used to tag routes.
, One community value might affect how the receiving router sets local
preference, while another might cause the route to be filtered at another
router.
Community attribute usage is not standardized, which gives potential for
misconfiguration.
◉ ARP (process). Answer: 1. Host queries with IP address - broadcast.
2. Host with IP address responds with MAC address - unicast.
3. When host receives reply, adds to ARP table.
4. To send packets, host puts IP packet inside Ethernet frame using MAC address
destination.
◉ Hubs vs. Switches. Answer: Hub: Broadcast medium where all packets on the
network are seen everywhere.
Switch: Partitions LAN into separate broadcast domains / LAN segments. Frames
bound for a host in the same segment aren't forwarded to other segments.
◉ Switch Table (definition). Answer: Maps destination MAC address to switch
output ports
100% aCCurate QuestioNs & aNswers
guaraNteed a
◉ BGP Paper:
Local Preference. Answer: Influences which BGP route will be chosen for each
destination prefix.
Done by adding / deleting / modifying route attributes in BGP advertiesments.
◉ BGP Paper:
Locally-Controlled Attributes for BGP Decision Process (2). Answer: 1. Local
preference
2. Lowest IGP cost to border router
◉ BGP Paper:
Neighbor-Controlled Attributes for BGP Decision Process (2). Answer: 1. AS
path length
2. MED
,◉ BGP Paper:
Filtering. Answer: Eliminates certain routes from consideration and controls
who they will be exported to.
May be applied before preference (inbound filtering) and/or after preference
(outbound filtering).
Done by instructing routers to ignore advertisements with attributes matching
certain values or ranges.
◉ BGP Paper:
Tagging. Answer: Allows an operator to associate additional state with a route,
which can be used to coordinate decisions made by a group of routers in an
AS, or to share context across AS boundaries.
The key mechanism is the community attribute.
◉ BGP Paper:
Community Attribute. Answer: A variable-length string used to tag routes.
, One community value might affect how the receiving router sets local
preference, while another might cause the route to be filtered at another
router.
Community attribute usage is not standardized, which gives potential for
misconfiguration.
◉ ARP (process). Answer: 1. Host queries with IP address - broadcast.
2. Host with IP address responds with MAC address - unicast.
3. When host receives reply, adds to ARP table.
4. To send packets, host puts IP packet inside Ethernet frame using MAC address
destination.
◉ Hubs vs. Switches. Answer: Hub: Broadcast medium where all packets on the
network are seen everywhere.
Switch: Partitions LAN into separate broadcast domains / LAN segments. Frames
bound for a host in the same segment aren't forwarded to other segments.
◉ Switch Table (definition). Answer: Maps destination MAC address to switch
output ports
