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Exam Code: 400-101 (Practice Exam Latest Test Questions VCE PDF)
Exam Name: CCIE Routing and Switching (v5.0)
Certification Provider: Cisco
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2021 Jul ccie 400 101:
Q301. Which two options are contained in the MSG part of a syslog message? (Choose two.)
A. TAG field
B. CONTENT field
C. three-digit priority value
D. IP address of the sending device
E. TLS port number
Answer: A,B
Q302. What is a reason for 6PE to use two MPLS labels in the data plane instead of one?
A. 6PE allows penultimate hop popping and has a requirement that all P routers do not have to be IPv6 aware.
B. 6PE does not allow penultimate hop popping.
C. It allows MPLS traffic engineering to work in a 6PE network.
D. It allows 6PE to work in an MPLS network where 6VPE is also deployed.
Answer: A
Explanation:
Q. Why does 6PE use two MPLS labels in the data plane?
A. 6PE uses two labels:
. The top label is the transport label, which is assigned hop-by-hop by the Label Distribution Protocol (LDP) or by MPLS traffic engineering (TE).
. The bottom label is the label assigned by the Border Gateway Protocol (BGP) and advertised by the internal BGP (iBGP) between the Provider Edge (PE) routers.
When the 6PE was released, a main requirement was that none of the MPLS core routers (the P routers) had to be IPv6-aware. That requirement drove the need for two labels in the data plane. There are two reasons why the 6PE needs both labels.
PHP Functionality
If only the transport label were used, and if penultimate hop popping (PHP) were used, the penultimate hop router (the P router) would need to understand IPv6.
With PHP, this penultimate hop router would need to remove the MPLS label and forward the packet as an IPv6 packet. This P router would need to know that the packet is IPv6 because the P router would need to use the correct Layer 2 encapsulation type for IPv6. (The encapsulation type is different for IPv6 and IPv4; for example, for Ethernet, the encapsulation type is 0x86DD for IPv6, while it is 0x0800 for IPv4.) If the penultimate hop router is not IPv6-capable, it would likely put the Layer 2 encapsulation type for IPv4 for the IPv6 packet. The egress PE router would then believe that the packet was IPv4. There is time-to-live (TTL) processing in both the IPv4 and IPv6 headers. In IPv6, the field is called Hop Limit. The IPv4 and IPv6 fields are at different locations in the headers. Also, the Header Checksum in the IPv4 header would also need to be changed; there is no Header Checksum field in IPv6. If the penultimate hop router is not IPv6-capable, it would cause the IPv6 packet to be malformed since the router expects to find the TTL field and Header Checksum field in the header. Because of these differences, the penultimate hop router would need to know it is an IPv6 packet. How would this router know that the packet is an IPv6 packet, since it did not assign a label to the IPv6 Forwarding Equivalence Class (FEC), and there is no encapsulation field in the MPLS header? It could scan for the first nibble after the label stack and determine that the packet is IPv6 if the value is 6. However, that implies that the penultimate hop router needs to be IPv6-capable. This scenario could work if the explicit null label is used (hence no PHP). However, the decision was to require PHP.
Load Balancing
Typical load balancing on a P router follows this process. The P router goes to the end of the label stack and determines if it is an IPv4 packet by looking at the first nibble after the label stack.
. If the nibble has a value of 4, the MPLS payload is an IPv4 packet, and the P router load balances by hashing the source and destination IPv4 addresses.
. If the P router is IPv6-capable and the value of the nibble is 6, the P router load balances by hashing the source and destination IPv6 addresses.
. If the P router is not IPv6-capable and the value of the nibble is not 4 (it could be 6 if the packet is an IPv6 packet), the P router determines it is not an IPv4 packet and makes the load balancing decision based on the bottom label. In the 6PE scenario, imagine there are two egress PE routers advertising one IPv6 prefix in BGP towards the ingress PE router. This IPv6 prefix would be advertised with two different labels in BGP. Hence, in the data plane, the bottom label would be either of the two labels. This would allow a P router to load balance on the bottom label on a per-flow basis. If 6PE used only the transport label to transport the 6PE packets through the MPLS core, the P routers would not be able to load balance these packets on a per-flow basis unless the P routers were IPv6-capable. If the P routers were IPv6-capable, they could use the source and destination IPv6 addresses in order to make a load balancing decision.
Reference: http://www.cisco.com/c/en/us/support/docs/multiprotocol-label-switching-mpls/mpls/116061-qa-6pe-00.html
Q303. Which technology facilitates dynamic tunnel establishment in DMVPN?
A. CEF
B. mGRE
C. a dynamic routing protocol
D. NHRP
Answer: D
Q304. Refer to the exhibit.
If EIGRP is configured between two routers as shown in this output, which statement about their EIGRP relationship is true?
A. The routers will establish an EIGRP relationship successfully.
B. The routers are using different authentication key-strings.
C. The reliability metric is enabled.
D. The delay metric is disabled.
Answer: C
Explanation:
The 5 K values used in EIGRP are:
K1 = Bandwidth modifier
K2 = Load modifier
K3 = Delay modifier
K4 = Reliability modifier
K5 = Additional Reliability modifier
However, by default, only K1 and K3 are used (bandwidth and delay). In this output we see that K1, K3, and K4 (Reliability) are all set.
Q305. Which additional feature must be enabled on a switch to allow PIM snooping to function correctly?
A. IGMP snooping
B. port security
C. storm control
D. dynamic ARP inspection
Answer: A
Up to the immediate present ccie written dumps 400-101:
Q306. Which statement is true about trunking?
A. Cisco switches that run PVST+ do not transmit BPDUs on nonnative VLANs when using a dot1q trunk.
B. When removing VLAN 1 from a trunk, management traffic such as CDP is no longer passed in that VLAN.
C. DTP only supports autonegotiation on 802.1q and does not support autonegotiation for ISL.
D. DTP is a point-to-point protocol.
Answer: D
Explanation:
Ethernet trunk interfaces support different trunking modes. You can set an interface as trunking or nontrunking or to negotiate trunking with the neighboring interface. To autonegotiate trunking, the interfaces must be in the same VTP domain. Trunk negotiation is managed by the Dynamic Trunking Protocol (DTP), which is a Point-to-Point Protocol. However, some internetworking devices might forward DTP frames improperly, which could cause misconfigurations.
Reference: http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750/software/release/12-2_55_se/configuration/guide/scg3750/swvlan.html
Q307. Which component of the BGP ORF can you use to permit and deny routing updates?
A. match
B. action
C. AFI
D. SAFI
E. ORF type
Answer: A
Q308. Refer to the exhibit.
Which configuration is missing that would enable SSH access on a router that is running Cisco IOS XE Software?
A. int Gig0/0/0
management-interface
B. class-map ssh-class
match access-group protect-ssh
policy-map control-plane-in
class ssh-class
police 80000 conform transmit exceed drop
control-plane
service-policy input control-plane-in
C. control-plane host
management-interface GigabitEthernet0/0/0 allow ssh
D. interface Gig0/0/0
ip access-group protect-ssh in
Answer: C
Explanation:
The feature Management Plane Protection (MPP) allows an administrator to restrict on which interfaces management traffic can be received by a device. This allows the administrator additional control over a device and how the device is accessed. This example shows how to enable the MPP in order to only allow SSH and HTTPS on the GigabitEthernet0/1 interface:
!
control-plane host
management-interface GigabitEthernet 0/1 allow ssh https
!
Reference: http://www.cisco.com/c/en/us/support/docs/ip/access-lists/13608-21.html
Q309. MPLS LDP IGP synchronization is configured on a link. The OSPF adjacency on that link is UP but MPLS LDP synchronization is not achieved. Which statement about this scenario is true?
A. The router excludes the link from its OSPF LSA type 1.
B. The router flushes its own router LSA.
C. The router advertises the link in its router LSA with max-metric.
D. The router advertises an LSA type 2 for this link, with the metric set to max-metric.
E. The router advertises the link and OSPF adjacency as it would when the synchronization is achieved.
Answer: C
Explanation:
To enable LDP-IGP Synchronization on each interface that belongs to an OSPF or IS-IS process, enter the mpls ldp sync command. If you do not want some of the interfaces to have LDP-IGP Synchronization enabled, issue the no mpls ldp igp sync command on those interfaces. If the LDP peer is reachable, the IGP waits indefinitely (by default) for synchronization to be achieved. To limit the length of time the IGP session must wait, enter the mpls ldp igp sync holddown command. If the LDP peer is not reachable, the IGP establishes the adjacency to enable the LDP session to be established. When an IGP adjacency is established on a link but LDP-IGP Synchronization is not yet achieved or is lost, the IGP advertises the max-metric on that link.
Reference: http://www.cisco.com/c/en/us/td/docs/ios/12_0s/feature/guide/fsldpsyn.html
Q310. Refer to the exhibit.
R3 prefers the path through R1 to reach host 10.1.1.1.
Which option describes the reason for this behavior?
A. The OSPF reference bandwidth is too small to account for the higher speed links through R2.
B. The default OSPF cost through R1 is less than the cost through R2.
C. The default OSPF cost through R1 is more than the cost through R2.
D. The link between R2 and R1 is congested.
Answer: A
Explanation:
The default formula to calculate OSPF bandwidth is BW = Bandwidth Reference / interface
bandwidth [bps] = 10^8 / / interface bandwidth [bps]
BW of the R1-R3 link = 10^8 / 100Mbps = 10^8 / 10^8 = 1
BW of the R2-R3 link = 10^8 / 1Gbps = 10^8 / 10^9 = 1 (round up)
Therefore OSPF considers the two above links have the same Bandwidth -> R3 will go to 10.1.1.1 via the R1-R3 link. The solution here is to increase the Bandwidth Reference to a higher value using the “auto-cost reference-bandwidth” command under OSPF router mode. For example: Router(config)#router ospf 1 Router(config-router)#auto-cost reference-bandwidth 10000 This will increase the reference bandwidth to 10000 Mbps which increases the BW of the R2-R3 link to 10^10 / 10^8 = 100.