CertBus 2018 Hottest Cisco 400-101 CCIE Exam VCE and PDF Dumps for Free Download!
☆ 400-101 CCIE Exam PDF and VCE Dumps : 1379QAs Instant Download: https://www.certbus.com/400-101.html [100% 400-101 Exam Pass Guaranteed or Money Refund!!]
☆ Free view online pdf on CertBus free test 400-101 PDF: https://www.certbus.com/online-pdf/400-101.pdf
☆ CertBus 2018 Hottest 400-101 CCIE exam Question PDF Free Download from Google Drive Share: https://drive.google.com/file/d/0B_3QX8HGRR1mdEpkTFZvSDJDc2c/view?usp=sharing
Following 400-101 1379QAs are all new published by Cisco Official Exam Center
Do not worry about your CCIE Jul 22,2018 Latest 400-101 pdf exam preparation? Hand over your problems to CertBus in change of the CCIE Latest 400-101 QAs CCIE Routing and Switching Written v5.0 certifications! CertBus provides the latest Cisco CCIE Latest 400-101 vce exam preparation materials with PDF and VCEs. We CertBus guarantees you passing CCIE Latest 400-101 study guide exam for sure.
400-101 vce exams | 400-101 vce certification software, 400-101 download vce dumps. pass 400-101 exams with CertBus exam files. CertBus – 100% real 400-101 certification exam questions and answers. easily pass with a high score. CertBus – find all popular 400-101 exam certification study materials here. our expert team is ready to help you to get your certification easily.
We CertBus has our own expert team. They selected and published the latest 400-101 preparation materials from Cisco Official Exam-Center: https://www.certbus.com/400-101.html
Which two commands are required to enable multicast on a router, knowing that the receivers only
support IGMPv2? (Choose two.)
A. ip pim rp-address
B. ip pim ssm
C. ip pim sparse-mode
D. ip pim passive
Sparse mode logic (pull mode) is the opposite of Dense mode logic (push mode), in Dense mode
it is supposed that in every network there is someone who is requesting the multicast traffic so
PIM-DM routers begin by flooding the multicast traffic out of all their interfaces except those from
where a prune message is received to eliminate the
Refer to the exhibit.
R1 has an EBGP session to ISP 1 and an EBGP session to ISP 2. R1 receives the same prefixes
through both links.
Which configuration should be applied so that the link between R1 and ISP 2 will be preferred for
outgoing traffic (R1 to ISP 2)?
A. Increase local preference on R1 for received routes
B. Decrease local preference on R1 for received routes
C. Increase MED on ISP 2 for received routes
D. Decrease MED on ISP 2 for received routes
Local preference is an indication to the AS about which path has preference to exit the AS in order
to reach a certain network. A path with higher local preference is preferred more. The default value
of preference is 100.
Why would a rogue host that is running a DHCP server on a campus LAN network present a
A. It may allocate IP addresses from an unknown subnet to the users.
B. All multicast traffic can be sniffed by using the DHCP multicast capabilities.
C. The CPU utilization of the first hop router can be overloaded by exploiting DHCP relay open
D. A potential man-in-the-middle attack can be used against the clients.
Which statement is true about TCN propagation?
A. The originator of the TCN immediately floods this information through the network.
B. The TCN propagation is a two step process.
C. A TCN is generated and sent to the root bridge.
D. The root bridge must flood this information throughout the network.
New Topology Change Mechanisms
When an 802.1D bridge detects a topology change, it uses a reliable mechanism to first notify the
This is shown in this diagram:
Once the root bridge is aware of a change in the topology of the network, it sets the TC flag on the
BPDUs it sends out, which are then relayed to all the bridges in the network. When a bridge
receives a BPDU with the TC flag bit set, it reduces its bridging-table aging time to forward delay
seconds. This ensures a relatively quick flush of stale information. Refer to Understanding
Spanning-Tree Protocol Topology Changes for more information on this process. This topology
change mechanism is deeply remodeled in RSTP. Both the detection of a topology change and its
propagation through the network evolve.
Topology Change Detection
In RSTP, only non-edge ports that move to the forwarding state cause a topology change. This
means that a loss of connectivity is not considered as a topology change any more, contrary to
802.1D (that is, a port that moves to blocking no longer generates a TC). When a RSTP bridge
detects a topology change, these occur:
It starts the TC While timer with a value equal to twice the hello-time for all its non-edge
designated ports and its root port, if necessary.
It flushes the MAC addresses associated with all these ports.
Note: As long as the TC While timer runs on a port, the BPDUs sent out of that port have the TC
BPDUs are also sent on the root port while the timer is active.
Topology Change Propagation
When a bridge receives a BPDU with the TC bit set from a neighbor, these occur:
It clears the MAC addresses learned on all its ports, except the one that receives the topology
It starts the TC While timer and sends BPDUs with TC set on all its designated ports and root port
(RSTP no longer uses the specific TCN BPDU, unless a legacy bridge needs to be notified).
This way, the TCN floods very quickly across the whole network. The TC propagation is now a one
step process. In fact, the initiator of the topology change floods this information throughout the
network, as opposed to 802.1D where only the root did. This mechanism is much faster than the
802.1D equivalent. There is no need to wait for the root bridge to be notified and then maintain the
topology change state for the whole network for seconds.
In just a few seconds, or a small multiple of hello-times, most of the entries in the CAM tables of
the entire network (VLAN) flush. This approach results in potentially more temporary flooding, but
on the other hand it clears potential stale information that prevents rapid connectivity restitution.
Which statement is true about loop guard?
A. Loop guard only operates on interfaces that are considered point-to-point by the spanning tree.
B. Loop guard only operates on root ports.
C. Loop guard only operates on designated ports.
D. Loop guard only operates on edge ports.
Understanding How Loop Guard Works
Unidirectional link failures may cause a root port or alternate port to become designated as root if
BPDUs are absent. Some software failures may introduce temporary loops in the network. Loop
guard checks if a root port or an alternate root port receives BPDUs. If the port is receiving
BPDUs, loop guard puts the port into an inconsistent state until it starts receiving BPDUs again.
Loop guard isolates the failure and lets spanning tree converge to a stable topology without the
failed link or bridge.
You can enable loop guard per port with the set spantree guard loop command.
Note When you are in MST mode, you can set all the ports on a switch with the set spantree
global-defaults loop-guard command.
When you enable loop guard, it is automatically applied to all of the active instances or VLANs to
which that port belongs. When you disable loop guard, it is disabled for the specified ports.
Disabling loop guard moves all loop-inconsistent ports to the listening state.
If you enable loop guard on a channel and the first link becomes unidirectional, loop guard blocks
the entire channel until the affected port is removed from the channel. Figure 8-6 shows loop
guard in a triangle switch configuration.
Figure 8-6 Triangle Switch Configuration with Loop Guard
Figure 8-6 illustrates the following configuration:
Switches A and B are distribution switches.
Switch C is an access switch.
Loop guard is enabled on ports 3/1 and 3/2 on Switches A, B, and C.
Use loop guard only in topologies where there are blocked ports. Topologies that have no blocked
ports, which are loop free, do not need to enable this feature. Enabling loop guard on a root switch
has no effect but provides protection when a root switch becomes a nonroot switch.
Follow these guidelines when using loop guard:
Do not enable loop guard on PortFast-enabled or dynamic VLAN ports.
Do not enable PortFast on loop guard-enabled ports.
Do not enable loop guard if root guard is enabled.
Do not enable loop guard on ports that are connected to a shared link.
Note: We recommend that you enable loop guard on root ports and alternate root ports on access
Loop guard interacts with other features as follows:
Loop guard does not affect the functionality of UplinkFast or BackboneFast.
Root guard forces a port to always be designated as the root port. Loop guard is effective only if
the port is a root port or an alternate port. Do not enable loop guard and root guard on a port at the
PortFast transitions a port into a forwarding state immediately when a link is established. Because
a PortFast-enabled port will not be a root port or alternate port, loop guard and PortFast cannot be
configured on the same port. Assigning dynamic VLAN membership for the port requires that the
port is PortFast enabled. Do not configure a loop guard-enabled port with dynamic VLAN
If your network has a type-inconsistent port or a PVID-inconsistent port, all BPDUs are dropped
until the misconfiguration is corrected. The port transitions out of the inconsistent state after the
message age expires. Loop guard ignores the message age expiration on type-inconsistent ports
and PVID-inconsistent ports. If the port is already blocked by loop guard, misconfigured BPDUs
that are received on the port make loop guard recover, but the port is moved into the type-
inconsistent state or PVID-inconsistent state.
In high-availability switch configurations, if a port is put into the blocked state by loop guard, it
remains blocked even after a switchover to the redundant supervisor engine. The newly activated
supervisor engine recovers the port only after receiving a BPDU on that port.
Loop guard uses the ports known to spanning tree. Loop guard can take advantage of logical ports
provided by the Port Aggregation Protocol (PAgP). However, to form a channel, all the physical
ports grouped in the channel must have compatible configurations. PAgP enforces uniform
configurations of root guard or loop guard on all the physical ports to form a channel.
These caveats apply to loop guard:
Which command is used to enable EtherChannel hashing for Layer 3 IP and Layer 4 port-based
A. mpls ip cef
B. port-channel ip cef
C. mpls ip port-channel cef
D. port-channel load balance
E. mpls ip load-balance
F. ip cef EtherChannel channel-id XOR L4
G. ip cef connection exchange
Which two options does Cisco PfR use to control the entrance link selection with inbound
optimization? (Choose two.)
A. Prepend extra AS hops to the BGP prefix.
B. Advertise more specific BGP prefixes (longer mask).
C. Add (prepend) one or more communities to the prefix that is advertised by BGP.
D. Have BGP dampen the prefix.
Explanation: PfR Entrance Link Selection Control Techniques
The PfR BGP inbound optimization feature introduced the ability to influence inbound traffic. A
network advertises reachability of its inside prefixes to the Internet using eBGP advertisements to
its ISPs. If the same prefix is advertised to more than one ISP, then the network is multihoming.
PfR BGP inbound optimization works best with multihomed networks, but it can also be used with
a network that has multiple connections to the same ISP. To implement BGP inbound
optimization, PfR manipulates eBGP advertisements to influence the best entrance selection for
traffic bound for inside prefixes. The benefit of implementing the best entrance selection is limited
to a network that has more than one ISP connection.
To enforce an entrance link selection, PfR offers the following methods:
BGP Autonomous System Number Prepend When an entrance link goes out-of-policy (OOP) due
to delay, or in images prior to Cisco IOS Releases 15.2(1) T1 and 15.1(2)S, and PfR selects a
best entrance for an inside prefix, extra autonomous system hops are prepended one at a time (up
to a maximum of six) to the inside prefix BGP advertisement over the other entrances. In Cisco
IOS Releases 15.2(1)T1, 15.1(2)S, and later releases, when an entrance link goes out-of policy
(OOP) due to unreachable or loss reasons, and PfR selects a best entrance for an inside prefix,
six extra autonomous system hops are prepended immediately to the inside prefix BGP
advertisement over the other entrances. The extra autonomous system hops on the other
entrances increase the probability that the best entrance will be used for the inside prefix. When
the entrance link is OOP due to unreachable or loss reasons, six extra autonomous system hops
are added immediately to allow the software to quickly move the traffic away from the old entrance
link. This is the default method PfR uses to control an inside prefix, and no user configuration is
BGP Autonomous System Number Community Prepend
When an entrance link goes out-of-policy (OOP) due to delay, or in images prior to Cisco IOS
(1)T1 and 15.1(2)S, and PfR selects a best entrance for an inside prefix, a BGP prepend
community is attached one at a time (up to a maximum of six) to the inside prefix BGP
advertisement from the network to another autonomous system such as an ISP. In Cisco IOS
Releases 15.2(1)T1, 15.1(2)S, and later releases, when an entrance link goes out-of-policy (OOP)
due to unreachable or loss reasons, and PfR selects a best entrance for an inside prefix, six BGP
prepend communities are attached to the inside prefix BGP advertisement. The BGP prepend
community will increase the number of autonomous system hops in the advertisement of the
inside prefix from the ISP to its peers. Autonomous system prepend BGP community is the
preferred method to be used for PfR BGP inbound optimization because there is no risk of the
local ISP filtering the extra autonomous system hops. There are some issues, for example, not all
ISPs support the BGP prepend community, ISP policies may ignore or modify the autonomous
system hops, and a transit ISP may filter the autonomous system path. If you use this method of
inbound optimization and a change is made to an autonomous system, you must issue an
outbound reconfiguration using the “clear ip bgp” command.
What action will a BGP route reflector take when it receives a prefix marked with the community
attribute NO ADVERTISE from a client peer?
A. It will advertise the prefix to all other client peers and non-client peers.
B. It will not advertise the prefix to EBGP peers.
C. It will only advertise the prefix to all other IBGP peers.
D. It will not advertise the prefix to any peers.
Refer to the exhibit.
R1 is not learning about the 172.16.10.0 subnet from the BGP neighbor R2 (220.127.116.11).
What can be done so that R1 will learn about this network?
A. Disable auto-summary on R2.
B. Configure an explicit network command for the 172.16.10.0 subnet on R2.
C. Subnet information cannot be passed between IBGP peers.
D. Disable auto-summary on R1.
By default, BGP does not accept subnets redistributed from IGP. To advertise and carry subnet
routes in BGP, use an explicit network command or the no auto-summary command. If you disable
auto-summarization and have not entered a network command, you will not advertise network
routes for networks with subnet routes unless they contain a summary route.
Refer to the exhibit.
Why is AS 65333 in parentheses?
A. It is an external AS.
B. It is a confederation AS.
C. It is the AS of a route reflector.
D. It is our own AS.
E. A route map has been applied to this route.
F. The BGP next hop is unreachable.
CertBus exam braindumps are pass guaranteed. We guarantee your pass for the 400-101 exam successfully with our Cisco materials. CertBus CCIE Routing and Switching Written v5.0 exam PDF and VCE are the latest and most accurate. We have the best Cisco in our team to make sure CertBus CCIE Routing and Switching Written v5.0 exam questions and answers are the most valid. CertBus exam CCIE Routing and Switching Written v5.0 exam dumps will help you to be the Cisco specialist, clear your 400-101 exam and get the final success.
400-101 Latest questions and answers on Google Drive(100% Free Download): https://drive.google.com/file/d/0B_3QX8HGRR1mdEpkTFZvSDJDc2c/view?usp=sharing
400-101 Cisco exam dumps (100% Pass Guaranteed) from CertBus: https://www.certbus.com/400-101.html [100% Exam Pass Guaranteed]
Why select/choose CertBus?
Millions of interested professionals can touch the destination of success in exams by certbus.com. products which would be available, affordable, updated and of really best quality to overcome the difficulties of any course outlines. Questions and Answers material is updated in highly outclass manner on regular basis and material is released periodically and is available in testing centers with whom we are maintaining our relationship to get latest material.