CCNP EXAM QUESTIONS AND
CORRECT ANSWERS ALREADY
PASSED
What is the hop-by-hop routing paradigm of BGP? - Answer-BGP specifies that it can
advertise to its peers in neighboring AS's only routes that it uses.<br />BGP cannot
influence how a neighboring AS will route your traffic BUT it can influence how your
traffic gets to the neighboring AS. <br /> BGP
What are the 4 categories of BGP attributes and what do they mean? - Answer-Well-
known Mandatory - Must be supported and propagated.<br />Well-known Discretionary
- Must be supported; propagation optional.<br />Optional Transitive - Marked as partial
if unsupported by neighbor.<br />Option Nontransitive - Deleted is unsupported by
neighbor. <br /> BGP
What are the administrative distances of eBGP and iBGP? - Answer-eBGP = 20<br
/>iBGP = 200<br /> BGP
What is the BGP Synchronization requirement and what does is prevent? When should
it be left disabled? When should it be enabled? - Answer-Rule: Router must be known
by an IGP before it may be advertised by BGP peers.<br />Prevents "blackholes" when
AS is a transit network and not all speaker are running BGP<br />Should be left on it AS
is a transit AS and not all routers run BGP.<br /> BGP
What are the 3 BGP tables and what is in them? - Answer-BGP Table - BGP topology
database, information <br />BGP Neighbor Table - list of connected neighbors<br />IP
Routing Table - Duh.<br /> BGP
What is the difference between iBGP and eBGP? - Answer-eBGP is an adjacency
between BGP peers in different AS; iBGP peers are in same AS. BGP
What are the 4 BGP packet types? What do they contain? - Answer-Open - Version,
AS, Hold Time, BGP Router ID, Optional Parameters<br />Keepalive - Sent every 60
seconds by default; hold time 180 Seconds.<br />Update - Information on only ONE
path; <br />Notification - When error condition detected<br /> BGP
What are the 6 BGP Neighbor states? - Answer-Idle - Router looking in routing table to
see if route exists to neighbor. <br /><br />[Active - When no response to Open
message] <br /><br />Connect - Router found route to neighbor and has performed the
, TCP three-way handshake<br /><br />Open Sent - Open message sent with BGP
parameters for the BGP session.<br /><br />Open Confirm - Router recieved agreement
on parameters for establishing the session. (If no response to open message, routers
goes to "Active.")<br /><br />Established - Only now are update, keepalive and
notification messages sent.<br /> BGP
What does BGP use for communication? What advantage does it offer? - Answer-TCP
port 179<br />Reliability; uses sliding window<br />Triggered, incremental updates
made very efficient<br /> BGP
What is the full mesh versus partial mesh IBGP and what are the implications of each? -
Answer-Partial mesh iBPG is where not all BGP speaks within and AS have an
established neighbor relationship. <br />Full mesh is every BGP speaker has a neighbor
(peer) with each other. <br />Routing updates are not replcated in iBPG the peers do
not pass it down 2nd hand.<br /> BGP
After the path selection process, what does BGP do with the route? - Answer-Places it
in the routing table. BGP
Explain the Next-Hop attribute. How does this differ from IGP's? In what environment
might this be problematic? - Answer-WM<br />Next hop address is entry point into the
next AS along the path to that destination network. It does a recursive lookup to the
routing table which should have learned the route from its IGP.<br />in IBGP the next
hop advertised by EBGP should be carried into IBGP.<br />In NBMA if the peer does
not have direction communication with the address it is a problem.<br /> BGP
Explain the Origin attribute. - Answer-WM<br />One of three values: <br />IGP - Route
is interior to the originating AS. (BGP table shows "i")<br />EGP - Route learned via
EGP. (BGP table shows "e")<br />Incomplete - Routes origin is unknown, usually when
redistributed. (BGP table shows "?")<br /> BGP
Explain the Local Preference attribute.<br /> - Answer-WD<br />Dictates which path is
preferred to exit the AS.<br />Higher is is preferred, default is 100 on Cisco.<br
/>Obviously for this to be relevant there must be multiple exit points for the route.<br
/>"Influences outbound traffic for an AS"<br /> BGP
Explain the Community attribute. - Answer-OT<br />Allows the router to "tag" and thus
implement policy based on this tag.<br /> BGP
Explain the MED attribute. - Answer-ON<br />Displayed as metric in Cisco IOS; lower is
preferred. Default is 0. Indicated to external AS the preferred path into the AS.<br
/>"Influence inbound traffic to an AS"<br />By default ONLY compares if neighbors AS
is same for all routes being considered unless the bgp always-compare-med command
is configured.<br /> BGP
CORRECT ANSWERS ALREADY
PASSED
What is the hop-by-hop routing paradigm of BGP? - Answer-BGP specifies that it can
advertise to its peers in neighboring AS's only routes that it uses.<br />BGP cannot
influence how a neighboring AS will route your traffic BUT it can influence how your
traffic gets to the neighboring AS. <br /> BGP
What are the 4 categories of BGP attributes and what do they mean? - Answer-Well-
known Mandatory - Must be supported and propagated.<br />Well-known Discretionary
- Must be supported; propagation optional.<br />Optional Transitive - Marked as partial
if unsupported by neighbor.<br />Option Nontransitive - Deleted is unsupported by
neighbor. <br /> BGP
What are the administrative distances of eBGP and iBGP? - Answer-eBGP = 20<br
/>iBGP = 200<br /> BGP
What is the BGP Synchronization requirement and what does is prevent? When should
it be left disabled? When should it be enabled? - Answer-Rule: Router must be known
by an IGP before it may be advertised by BGP peers.<br />Prevents "blackholes" when
AS is a transit network and not all speaker are running BGP<br />Should be left on it AS
is a transit AS and not all routers run BGP.<br /> BGP
What are the 3 BGP tables and what is in them? - Answer-BGP Table - BGP topology
database, information <br />BGP Neighbor Table - list of connected neighbors<br />IP
Routing Table - Duh.<br /> BGP
What is the difference between iBGP and eBGP? - Answer-eBGP is an adjacency
between BGP peers in different AS; iBGP peers are in same AS. BGP
What are the 4 BGP packet types? What do they contain? - Answer-Open - Version,
AS, Hold Time, BGP Router ID, Optional Parameters<br />Keepalive - Sent every 60
seconds by default; hold time 180 Seconds.<br />Update - Information on only ONE
path; <br />Notification - When error condition detected<br /> BGP
What are the 6 BGP Neighbor states? - Answer-Idle - Router looking in routing table to
see if route exists to neighbor. <br /><br />[Active - When no response to Open
message] <br /><br />Connect - Router found route to neighbor and has performed the
, TCP three-way handshake<br /><br />Open Sent - Open message sent with BGP
parameters for the BGP session.<br /><br />Open Confirm - Router recieved agreement
on parameters for establishing the session. (If no response to open message, routers
goes to "Active.")<br /><br />Established - Only now are update, keepalive and
notification messages sent.<br /> BGP
What does BGP use for communication? What advantage does it offer? - Answer-TCP
port 179<br />Reliability; uses sliding window<br />Triggered, incremental updates
made very efficient<br /> BGP
What is the full mesh versus partial mesh IBGP and what are the implications of each? -
Answer-Partial mesh iBPG is where not all BGP speaks within and AS have an
established neighbor relationship. <br />Full mesh is every BGP speaker has a neighbor
(peer) with each other. <br />Routing updates are not replcated in iBPG the peers do
not pass it down 2nd hand.<br /> BGP
After the path selection process, what does BGP do with the route? - Answer-Places it
in the routing table. BGP
Explain the Next-Hop attribute. How does this differ from IGP's? In what environment
might this be problematic? - Answer-WM<br />Next hop address is entry point into the
next AS along the path to that destination network. It does a recursive lookup to the
routing table which should have learned the route from its IGP.<br />in IBGP the next
hop advertised by EBGP should be carried into IBGP.<br />In NBMA if the peer does
not have direction communication with the address it is a problem.<br /> BGP
Explain the Origin attribute. - Answer-WM<br />One of three values: <br />IGP - Route
is interior to the originating AS. (BGP table shows "i")<br />EGP - Route learned via
EGP. (BGP table shows "e")<br />Incomplete - Routes origin is unknown, usually when
redistributed. (BGP table shows "?")<br /> BGP
Explain the Local Preference attribute.<br /> - Answer-WD<br />Dictates which path is
preferred to exit the AS.<br />Higher is is preferred, default is 100 on Cisco.<br
/>Obviously for this to be relevant there must be multiple exit points for the route.<br
/>"Influences outbound traffic for an AS"<br /> BGP
Explain the Community attribute. - Answer-OT<br />Allows the router to "tag" and thus
implement policy based on this tag.<br /> BGP
Explain the MED attribute. - Answer-ON<br />Displayed as metric in Cisco IOS; lower is
preferred. Default is 0. Indicated to external AS the preferred path into the AS.<br
/>"Influence inbound traffic to an AS"<br />By default ONLY compares if neighbors AS
is same for all routes being considered unless the bgp always-compare-med command
is configured.<br /> BGP
