CCIE - BGP
What does the ORIGIN attribute tell you? correct answersWhether the
router was via redistribution or the network
originated
statement
what is the private ASN range? correct
answers64512-65535
what is the new ASN type byte njumber? correct answers4 (4
OCTET)
a 4 byte number, as an example, is dentoed by what? correct
answers1.1 (=256)
What port does BGP use for transport? correct
answersTCP 179
what tells you what address a BGP router is listening for BGP requests
on? correct
answersshow control-plane host open-
ports
where there is a multiple connections to a neighbour, what interface
would be
easiest tothe
peer against? correct answersthe
loopback
what is the TTL value of a eBGP peering? correct
answers1
what is the TTL value of an iBGP peering? correct
answers255
what determines becomes the TCP client? correct answersThe higher
router-id
Do you have to set the update-source on both sides? correct
answersNo,
should. but
If you youyou are forcing what is the
dont
TCP client
What is the driving motivation to use a loopback for iBGP peering? correct
be able to route around interface
answersTo
failures
What is the iBGP loop prevention mechanism? correct answersiBGP learned
routes are
not advertised to another iBGP
peer
What is the eBGP llop prevention mechanism? correct answersIt checks the
and if its AS_PATH is in the path it
AS_PATH
drops it
For iBGP peers, what are two mechnisms to allow iBGP learned routes to
be shared
with other iBGP peers? correct answerseither route reflectors /
mesh of iBGP or a full
confederations
peers.
,what 3 things does the BGP NLRI information contain? correct
Attributes, Next-
answersPrefix,
hop
What is a consequence of BGP not knowing the outgoing interface to the
next-hop?
correct answersIts able to route to it, and therefore there is no best path
selection, the
therefore andnext hop cannot be installed in the
routing table
Does iBGP processing updates change the next-hop value? correct
answersNo
What does eBGP have by default for the next hop value? correct
answersthe local
update-source for the neighbour (e.g.
loopback)
what one tool can we use to make full mesh config quicker? correct
group
answerspeer
s
What is the main disadvantage of full iBGP meshing? correct answersThe
control
scalin plane
g
what best path does a route reflector reflect to its peers? correct
answersIts own best
pat
h
What does a route reflector do when it recieves routes in with its own
cluster-id
correct in it?
answersIt drops the routes as this is a loop prevention
mechnism
What does the RR set the Originator-ID to? correct answersThe route
reflector client
Can a reflector reflect the non-client routes from non-client to non-
clients? correct
answersN
o
What two attributes in confederations prevent loops?
correct answersAS_CONFED_SEQUENCE and
AS_CONFED_SET
What is a hitless and easier to change, to RR or confed? correct
Confederations are a distruptive
answersRR.
change
Do you have to configure reflector details on both sides or just
one? correct one on the RR itself - client needs no special
answersJust
config
Wha are the three steps for confederation configuration? correct
answersEnable the BGP process, Specify the main AS number, Speify
other sub-AS that you peer with.
Are confederation AS considered in the ASP_PATH for path selection?
correct
answersYes, but only in that all the confederations in the path (in brackets)
a single
are seen as
AS
, What is an external confed peer? correct answersA poeer that is in the same
global
but in aAS,
different
confed AS
Can you use RR in a Confed? correct answersYes and this is recommended in
order toall routers in the confed are recieveing all the routes without using
ensure
a full mesh
At the end of the day, what is it that BGP tells you, or advertises to
you? correct IPv4 prefix, the prefix length, the attributes and the next-hop.
answersThe
Its up you
HOW to you
get TO the next
hop.
What is checked forst before a route is installed in the RIB? correct
answersCan
to the next- we get
hop?
What is one of the three solutions to resolve next-hop reachability
issues? correct
answersuse the next-hop self command. This done to the RR if this is
in the AS
What is the second of the three solutions to resolve next-hop
correct answersManually
reachability issues? change the next-hop using a route-map with
neighbor x.x.x.x
route-map yy in|
out
What is the third of the three solutions to resolve next-hop reachability
answersThird
issues? correctparty next hop, when routers are on the same IP subnet (like
DMVPN).
Acts like a route reflector, but for eBGP. Counfigure with "bgp next-hop route-
map XXX"
WHy do we use next-hop tracking? correct answersNext-hop tracking
makes BGP a function of IGP convergence, otherwise a failure of the
convergence
nexthop
take would
3 mins to converge while BGP keepalives withdraw the
next-hop
What is ways to provide NLRI origination? correct answersUsing the network
redistribution, aggregation, bgp
statement,
inject-map
Can you redistribute OSPF external routes? correct
answersNo
What weight and ORIGIN code does the network set the NLRI to?
correct
answers32768 and Origin
of i
What ORIGIN code does BGP create if the redistribute command is
used? correct
answersINCOMPLETE
(?)
If you use the network statement and I use the redistribute statement
what correct
win? path willanswersI will due to the locally
generated
In BGP redistrubtion what is automatically copied to BGP MED? correct
IGP
answersThe
metric
What does the ORIGIN attribute tell you? correct answersWhether the
router was via redistribution or the network
originated
statement
what is the private ASN range? correct
answers64512-65535
what is the new ASN type byte njumber? correct answers4 (4
OCTET)
a 4 byte number, as an example, is dentoed by what? correct
answers1.1 (=256)
What port does BGP use for transport? correct
answersTCP 179
what tells you what address a BGP router is listening for BGP requests
on? correct
answersshow control-plane host open-
ports
where there is a multiple connections to a neighbour, what interface
would be
easiest tothe
peer against? correct answersthe
loopback
what is the TTL value of a eBGP peering? correct
answers1
what is the TTL value of an iBGP peering? correct
answers255
what determines becomes the TCP client? correct answersThe higher
router-id
Do you have to set the update-source on both sides? correct
answersNo,
should. but
If you youyou are forcing what is the
dont
TCP client
What is the driving motivation to use a loopback for iBGP peering? correct
be able to route around interface
answersTo
failures
What is the iBGP loop prevention mechanism? correct answersiBGP learned
routes are
not advertised to another iBGP
peer
What is the eBGP llop prevention mechanism? correct answersIt checks the
and if its AS_PATH is in the path it
AS_PATH
drops it
For iBGP peers, what are two mechnisms to allow iBGP learned routes to
be shared
with other iBGP peers? correct answerseither route reflectors /
mesh of iBGP or a full
confederations
peers.
,what 3 things does the BGP NLRI information contain? correct
Attributes, Next-
answersPrefix,
hop
What is a consequence of BGP not knowing the outgoing interface to the
next-hop?
correct answersIts able to route to it, and therefore there is no best path
selection, the
therefore andnext hop cannot be installed in the
routing table
Does iBGP processing updates change the next-hop value? correct
answersNo
What does eBGP have by default for the next hop value? correct
answersthe local
update-source for the neighbour (e.g.
loopback)
what one tool can we use to make full mesh config quicker? correct
group
answerspeer
s
What is the main disadvantage of full iBGP meshing? correct answersThe
control
scalin plane
g
what best path does a route reflector reflect to its peers? correct
answersIts own best
pat
h
What does a route reflector do when it recieves routes in with its own
cluster-id
correct in it?
answersIt drops the routes as this is a loop prevention
mechnism
What does the RR set the Originator-ID to? correct answersThe route
reflector client
Can a reflector reflect the non-client routes from non-client to non-
clients? correct
answersN
o
What two attributes in confederations prevent loops?
correct answersAS_CONFED_SEQUENCE and
AS_CONFED_SET
What is a hitless and easier to change, to RR or confed? correct
Confederations are a distruptive
answersRR.
change
Do you have to configure reflector details on both sides or just
one? correct one on the RR itself - client needs no special
answersJust
config
Wha are the three steps for confederation configuration? correct
answersEnable the BGP process, Specify the main AS number, Speify
other sub-AS that you peer with.
Are confederation AS considered in the ASP_PATH for path selection?
correct
answersYes, but only in that all the confederations in the path (in brackets)
a single
are seen as
AS
, What is an external confed peer? correct answersA poeer that is in the same
global
but in aAS,
different
confed AS
Can you use RR in a Confed? correct answersYes and this is recommended in
order toall routers in the confed are recieveing all the routes without using
ensure
a full mesh
At the end of the day, what is it that BGP tells you, or advertises to
you? correct IPv4 prefix, the prefix length, the attributes and the next-hop.
answersThe
Its up you
HOW to you
get TO the next
hop.
What is checked forst before a route is installed in the RIB? correct
answersCan
to the next- we get
hop?
What is one of the three solutions to resolve next-hop reachability
issues? correct
answersuse the next-hop self command. This done to the RR if this is
in the AS
What is the second of the three solutions to resolve next-hop
correct answersManually
reachability issues? change the next-hop using a route-map with
neighbor x.x.x.x
route-map yy in|
out
What is the third of the three solutions to resolve next-hop reachability
answersThird
issues? correctparty next hop, when routers are on the same IP subnet (like
DMVPN).
Acts like a route reflector, but for eBGP. Counfigure with "bgp next-hop route-
map XXX"
WHy do we use next-hop tracking? correct answersNext-hop tracking
makes BGP a function of IGP convergence, otherwise a failure of the
convergence
nexthop
take would
3 mins to converge while BGP keepalives withdraw the
next-hop
What is ways to provide NLRI origination? correct answersUsing the network
redistribution, aggregation, bgp
statement,
inject-map
Can you redistribute OSPF external routes? correct
answersNo
What weight and ORIGIN code does the network set the NLRI to?
correct
answers32768 and Origin
of i
What ORIGIN code does BGP create if the redistribute command is
used? correct
answersINCOMPLETE
(?)
If you use the network statement and I use the redistribute statement
what correct
win? path willanswersI will due to the locally
generated
In BGP redistrubtion what is automatically copied to BGP MED? correct
IGP
answersThe
metric
