CCNP encore Exam Questions with Correct Answers| New Update Guaranteed Success
What are are the 32 bits contained in the vlan header? TPID tag protocol identifier - 16 bits
of 0x8100 to identify packet is an 802.1q packet
PCP priority code point - 3 bit field indicates a class of service as a part of layer 2 qos between
switches
DEI drop eligible indicator - 1 bit field indicates whether packet can be dropped when there is
bandwidth contention
VLAN ID - 12 bits that indicate the vlan
command to flush mac address table clear mac-address table dynamic
What is the CAM? content addressable memory - where the mac address table resides
What is the RIB? Routing information Base - table that contains the routing table; interfaces
with an up status and an IP auto inject their ip address in here
What is process switching? Where a general purpose CPU on a router is in charge of packet
switching; this is the fallback for CEF
What packets generally require process switching? packets sourced or destined to the
router, packets that are too complex for the hardware (such as an IP packet with IP options) or
packets that require extra information that is currently not known
What is the CEF? Cisco express forwarding - cisco proprietary switching mechanism using
application specific integrated circuits (ASICs) and network processing units (NPUs) for high
packet throughput; essentially hardware based router
What is TCAM? ternary content addressable memory - allows matching and evaluation of a
packet on more than one field. An extension of the CAM, it can idneitfy layer 2/3
source/destination addresses, protocol, QoS markins and so on. The CAM is binary, but the
TCAM is ternary, allowing for true, false, and don't care search results.
,How are TCAM entries stored? Value, mask and result format. Value indicates fields that
should be searched, mask indicates the field is of interest and should be queried, and result
indicates action that should be taken on match
What is centralized forwarding architecture? A route processor engine being equipped with
a forwarding engine so that it can make all the packet switching decisions.
What is distributed forwarding architecture? When the line cards contain the forwarding
engines; when a line card determines traffic should be sent out of a different interface, it will
send the data over a backplane switch fabric bypassing the RP.
What is the software FIB? a software CEF that contains the forwarding information base and
the adjacency table
What is the FIB? forwarding information base - built from the routing table, contains the
next hop ip for each network destination; used to make IP destination prefix based switching
decisions
What is the adjacency table? contains the directly connection next hop IP addresses and
their corresponding next hop mac addresses, as well as the egress interfaces mac address.
Populated from the ARP table
What is the hardware CEF? utilizes dCEF (distributed CEF) to have the line cards make the
forwarding decisions
what is the switching database manager allow you to do? modify ratios between tcam
tables (macs stored vs ips stored) with SDM templates
802.1D port states? disabled - admin off
,blocking - port is enabled but not forwarding; switch does not modify mac table, can only
receive BPDUs from other switches
listening - send or receive BPDUs but cannot forward other network traffic; duration of state is
STP forwarding time
learning - can now modify mac table with network traffic, cannot send other network traffic;
duration is STP forwarding time
forwarding - do everything
broken - discards packets due to detected issue
802.1D port types? root port - network port that connects to the root bridge or an upstream
switch; only one root port per vlan on switch
designated port - receives and forwards BPDU frames to other switches; provide connectivity
downstream; only one active designated port per link
blocking port - network port taht cannot forward traffic
802.1D root bridge top of STP path, all ports are designated
802.1D BPDU network packet used for network switches to identify and notify of changes in
topology
configuration BPDU - identifies root bridge, root ports, DPs and BPs.
topology change notification - communicates changes in layer 2 topology
802.1D root path cost combined cost for a specific path toward the root switch
802.1D system priority - 4 bit value indicates preference for switch t obe root bridge, default
is 32768
802.1d system id extension 12 bit value indicates the vlan that the BPDU correlates to.
System priority and system ID extension are combined as part of the switch's id of a bridge
, 802.1Droot bridge ID combination of the root bridge system mac address, system id
extension and system priority of root bridge
802.1D local bridge id combo of system mac, system id extension and system priority
802.1D max age max length of time a bridge port stores its BPDU info; default is 20 seconds
802.1D hello time interval that a BPDU is advertised out of a port, default is 2 seconds
forward delay amount of time a port stays in listening and learning mode; default is 15
seconds
802.1D default port costs 10 mb - 100 - 2000000
100 mb - 19 - 200000
1 gb - 4 - 20000
10 gb - 2 - 2000
20 gb - 1 - 1000
100 gb - 1 - 200
1 tb - 1 - 20
10 tb - 1 - 2
How 802.1D selects root bridge? looks at neighbor BPDU config, prefers lower bridge
identifier or lower system mac
how to select root port? lowest path cost, interface associated to lowest system priority of
advertising switch, int associated to lowest system mac, (when multiple links to same switch)
lowest port priority from advertising switch, (when multiple links to same switch) lower port
number from advertising switch
What are are the 32 bits contained in the vlan header? TPID tag protocol identifier - 16 bits
of 0x8100 to identify packet is an 802.1q packet
PCP priority code point - 3 bit field indicates a class of service as a part of layer 2 qos between
switches
DEI drop eligible indicator - 1 bit field indicates whether packet can be dropped when there is
bandwidth contention
VLAN ID - 12 bits that indicate the vlan
command to flush mac address table clear mac-address table dynamic
What is the CAM? content addressable memory - where the mac address table resides
What is the RIB? Routing information Base - table that contains the routing table; interfaces
with an up status and an IP auto inject their ip address in here
What is process switching? Where a general purpose CPU on a router is in charge of packet
switching; this is the fallback for CEF
What packets generally require process switching? packets sourced or destined to the
router, packets that are too complex for the hardware (such as an IP packet with IP options) or
packets that require extra information that is currently not known
What is the CEF? Cisco express forwarding - cisco proprietary switching mechanism using
application specific integrated circuits (ASICs) and network processing units (NPUs) for high
packet throughput; essentially hardware based router
What is TCAM? ternary content addressable memory - allows matching and evaluation of a
packet on more than one field. An extension of the CAM, it can idneitfy layer 2/3
source/destination addresses, protocol, QoS markins and so on. The CAM is binary, but the
TCAM is ternary, allowing for true, false, and don't care search results.
,How are TCAM entries stored? Value, mask and result format. Value indicates fields that
should be searched, mask indicates the field is of interest and should be queried, and result
indicates action that should be taken on match
What is centralized forwarding architecture? A route processor engine being equipped with
a forwarding engine so that it can make all the packet switching decisions.
What is distributed forwarding architecture? When the line cards contain the forwarding
engines; when a line card determines traffic should be sent out of a different interface, it will
send the data over a backplane switch fabric bypassing the RP.
What is the software FIB? a software CEF that contains the forwarding information base and
the adjacency table
What is the FIB? forwarding information base - built from the routing table, contains the
next hop ip for each network destination; used to make IP destination prefix based switching
decisions
What is the adjacency table? contains the directly connection next hop IP addresses and
their corresponding next hop mac addresses, as well as the egress interfaces mac address.
Populated from the ARP table
What is the hardware CEF? utilizes dCEF (distributed CEF) to have the line cards make the
forwarding decisions
what is the switching database manager allow you to do? modify ratios between tcam
tables (macs stored vs ips stored) with SDM templates
802.1D port states? disabled - admin off
,blocking - port is enabled but not forwarding; switch does not modify mac table, can only
receive BPDUs from other switches
listening - send or receive BPDUs but cannot forward other network traffic; duration of state is
STP forwarding time
learning - can now modify mac table with network traffic, cannot send other network traffic;
duration is STP forwarding time
forwarding - do everything
broken - discards packets due to detected issue
802.1D port types? root port - network port that connects to the root bridge or an upstream
switch; only one root port per vlan on switch
designated port - receives and forwards BPDU frames to other switches; provide connectivity
downstream; only one active designated port per link
blocking port - network port taht cannot forward traffic
802.1D root bridge top of STP path, all ports are designated
802.1D BPDU network packet used for network switches to identify and notify of changes in
topology
configuration BPDU - identifies root bridge, root ports, DPs and BPs.
topology change notification - communicates changes in layer 2 topology
802.1D root path cost combined cost for a specific path toward the root switch
802.1D system priority - 4 bit value indicates preference for switch t obe root bridge, default
is 32768
802.1d system id extension 12 bit value indicates the vlan that the BPDU correlates to.
System priority and system ID extension are combined as part of the switch's id of a bridge
, 802.1Droot bridge ID combination of the root bridge system mac address, system id
extension and system priority of root bridge
802.1D local bridge id combo of system mac, system id extension and system priority
802.1D max age max length of time a bridge port stores its BPDU info; default is 20 seconds
802.1D hello time interval that a BPDU is advertised out of a port, default is 2 seconds
forward delay amount of time a port stays in listening and learning mode; default is 15
seconds
802.1D default port costs 10 mb - 100 - 2000000
100 mb - 19 - 200000
1 gb - 4 - 20000
10 gb - 2 - 2000
20 gb - 1 - 1000
100 gb - 1 - 200
1 tb - 1 - 20
10 tb - 1 - 2
How 802.1D selects root bridge? looks at neighbor BPDU config, prefers lower bridge
identifier or lower system mac
how to select root port? lowest path cost, interface associated to lowest system priority of
advertising switch, int associated to lowest system mac, (when multiple links to same switch)
lowest port priority from advertising switch, (when multiple links to same switch) lower port
number from advertising switch
