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2021 Dec 400-101 ccie written exam number:
Q121. Refer to the exhibit.
Which statement is true?
A. R1 routes this pseudowire over MPLS TE tunnel 1 with transport label 20.
B. The default route 0.0.0.0/0 is available in the IPv4 routing table.
C. R1 is using an MPLS TE tunnel for this pseudowire, because the IP path is not available.
D. R1 has preferred-path configured for the pseudowire.
Answer: D
Explanation:
Verifying the Configuration: Example In the following example, the show mpls l2transport vc command shows the following information (in bold) about the VCs:
. VC 101 has been assigned a preferred path called Tunnel1. The default path is disabled because the preferred path specified that the default path should not be used if the preferred path fails.
. VC 150 has been assigned an IP address of a loopback address on PE2. The default path can be used if the preferred path fails.
Router# show mpls l2transport vc detail
Local interface. Gi0/0/0.1 up, line protocol up, Eth VLAN 222 up
Destination address: 10.16.16.16, VC ID. 101, VC status: up
Preferred path: Tunnel1, active
Default path: disabled
Tunnel label: 3, next hop point2point
Output interfacE. Tu1, imposed label stack {17 16}
Create timE. 00:27:31, last status change timE. 00:27:31
Signaling protocol: LDP, peer 10.16.16.16:0 up
MPLS VC labels: local 25, remote 16
Group ID. local 0, remote 6
MTU: local 1500, remote 1500
Remote interface description:
Sequencing: receive disabled, send disabled
VC statistics:
packet totals: receive 10, send 10
byte totals: receive 1260, send 1300
packet drops: receive 0, send 0
Reference: http://www.cisco.com/c/en/us/td/docs/ios/12_2sr/12_2sra/feature/guide/srtunsel.html#wp10 57815
Q122. What is a disadvantage of using aggressive mode instead of main mode for ISAKMP/IPsec establishment?
A. It does not use Diffie-Hellman for secret exchange.
B. It does not support dead peer detection.
C. It does not support NAT traversal.
D. It does not hide the identity of the peer.
Answer: D
Explanation:
IKE phase 1's purpose is to establish a secure authenticated communication channel by using the Diffie–Hellman key exchange algorithm to generate a shared secret key to encrypt further IKE communications. This negotiation results in one single bi-directional ISAKMP Security Association (SA). The authentication can be performed using either pre-shared key (shared secret), signatures, or public key encryption.Phase 1 operates in either Main Mode or Aggressive Mode. Main Mode protects the identity of the peers; Aggressive Mode does not.
Reference: http://en.wikipedia.org/wiki/Internet_Key_Exchange
Q123. Which three statements describe the characteristics of a VPLS architecture? (Choose three.)
A. It forwards Ethernet frames.
B. It maps MAC address destinations to IP next hops.
C. It supports MAC address aging.
D. It replicates broadcast and multicast frames to multiple ports.
E. It conveys MAC address reachability information in a separate control protocol.
F. It can suppress the flooding of traffic.
Answer: A,C,D
Explanation:
As a VPLS forwards Ethernet frames at Layer 2, the operation of VPLS is exactly the same as that found within IEEE 802.1 bridges in that VPLS will self learn source MAC address to port associations, and frames are forwarded based upon the destination MAC address. Like other 802.1 bridges, MAC address aging is supported.
Reference: http://www.cisco.com/en/US/products/hw/routers/ps368/products_white_paper09186a0080 1f6084.shtml
Q124. DRAG DROP
Drag and drop the RIP configuration command on the left to the function it performs on the right.
Answer:
Q125. Which three modes are valid PfR monitoring modes of operation? (Choose three.)
A. route monitor mode (based on BGP route changes)
B. RMON mode (based on RMONv1 and RMONv2 data)
C. passive mode (based on NetFlow data)
D. active mode (based on Cisco IP SLA probes)
E. fast mode (based on Cisco IP SLA probes)
F. passive mode (based on Cisco IP SLA probes)
Answer: C,D,E
Explanation:
Modes are:
Mode monitor passive
Passive monitoring is the act of PfR gathering information on user packets assembled into flows by Netflow. Passive monitoring is typically only recommended in Internet edge deployments because active probing is ineffective because of security policies that block probing. PfR, when enabled, automatically enables Netflow on the managed interfaces on the Border Routers. By aggregating this information on the Border Routers and periodically reporting the collected data to the Master Controller, the network prefixes and applications in use can automatically be learned.
Mode monitor active
Active monitoring is the act of generating Cisco IOS IP Service Level Agreements (SLAs) probes to generate test traffic for the purpose of obtaining information regarding the characteristics of the WAN links. PfR can either implicitly generates active probes when passive monitoring has identified destination hosts, or the network manager can explicitly configured probes in the PfR configuration. When jitter probes are used (common use case), Target Discovery is used to learn the respond address and to automatically generate the probes.
Mode monitor Fast
This mode generates active probes through all exists continuously at the configured probe frequency. This differs from either active or both modes in that these modes only generate probes through alternate paths (exits) in the event the current path is out-of-policy.
Reference: http://docwiki.cisco.com/wiki/PfR:Technology_Overview#Mode_monitor_passive
Most up-to-date ccie pdf download:
Q126. Which statement about VRRP is true?
A. It supports load balancing.
B. It can be configured with HSRP on a switch or switch stack.
C. It supports IPv4 and IPv6.
D. It supports encrypted authentication.
Answer: B
Explanation:
VRRP Limitations
. You can configure both HSRP and VRRP on a switch or switch stack. However, you cannot add a switch model that supports only one protocol to a stack that is configured for both protocols.
. The VRRP implementation on the switch does not support the MIB specified in RFC 2787.
. The VRRP implementation on the switch supports only text -based authentication.
. The switch supports VRRP only for IPv4.
Reference: http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750x_3560x/software/release/1 2-2_58_se/configuration/guide/3750xscg/swhsrp.html#pgfId-1107127
Q127. Refer to the exhibit.
R1, R2, and R3 have full network connectivity to each other, but R2 prefers the path through R3 to reach network 172.17.1.0/24. Which two actions can you take so that R2 prefers the path through R1 to reach 172.17.1.0/24? (Choose two.)
A. Set the reference bandwidth to 10000 on R1, R2, and R3.
B. Configure the cost on the link between R1 and R3 to be greater than 100 Mbps.
C. Set the reference bandwidth on R2 only.
D. Configure a manual bandwidth statement with a value of 1 Gbps on the link between R1 and R3.
E. Modify the cost on the link between R1 and R2 to be greater than 10 Gbps.
F. Configure a manual bandwidth statement with a value of 100 Mbps on the link between R1 and R2.
Answer: A,B
Explanation:
By default, the reference bandwidth used in Cisco routers is 100Mbps, so FastEthernet and above will have a cost of 1, so a gigabit interface and 10GE interface will be equal with a fastethernet. This is not ideal. If we change the reference bandwidth to 100000 then the faster links will be used. Changing the reference bandwidth needs to be done on all routers in the OSPF network. Increasing the cost on the R1-R3 link will also cause the traffic to take the more direct route.
Q128. How does having an EIGRP feasible successor speed up convergence?
A. EIGRP sends queries only if there is a feasible successor, which decreases the number of routers that are involved in convergence.
B. EIGRP sends queries only if there is not a feasible successor, which causes less control traffic to compete with data.
C. EIGRP immediately installs the loop-free alternative path in the RIB.
D. EIGRP preinstalls the feasible successor in the RIB in all cases, which causes traffic to switch more quickly.
Answer: C
Explanation:
Feasible Successor
. A next-hop router that serves as backup to the current successor.
. The condition is that the said router’s AD (or RD) is less than the FD of the current successor route.
. Once the feasible successor is selected, they are placed in the topology table. If a change in topology occurs which requires a new route, DUAL looks for the feasible successor and uses it as new route immediately, resulting in fast convergence.
Reference: http://routemyworld.com/2008/07/page/2/
Q129. Which two 802.1D port states are expected in a stable Layer 2 network? (Choose two.)
A. forwarding
B. learning
C. listening
D. blocking
E. disabled
Answer: A,D
Q130. Which option describes what the default RT filter indicates when you implement the BGP RT constrained route distribution feature?
A. A peer receives only a default route for each VRF.
B. A peer receives all routes, regardless of the RT value.
C. A peer receives routes only for RTs that are used on that router.
D. A peer receives no routes, regardless of the RT value.
Answer: B