Cisco 400-101 CCIE Routing and Switching Written Exam Online Training
Cisco 400-101 Online Training
The questions for 400-101 were last updated at Sep 15,2025.
- Exam Code: 400-101
- Exam Name: CCIE Routing and Switching Written Exam
- Certification Provider: Cisco
- Latest update: Sep 15,2025
What are two conditions that can cause UDLD to move an interface into the errdisable state? (Choose two.)
- A . A switch receives its own UDLD message on the same port it has sent it from.
- B . UDLD detects a mismatch between timer settings on neighboring switches.
- C . The list of detected neighbors in a received UDLD message is missing the receiving switch ID and port ID combination.
- D . An ACL denying all IP traffic is applied to a switchport.
- E . A port in normal UDLD mode fails to receive a UDLD message for a prolonged time period.
Which two statements about STP are true? (Choose two)
- A . To support load-balancing across redundant paths, the VAN-to-instance mapping must match on all
- B . switches in each path
- C . MST configurations are propagated throughout the VTP domain
- D . Only one version of STP can be active on a device at one time
- E . Rapid PVST+ and MST can be active on a device simultaneously
- F . MST supports up to four MST instances, including instance 0
Refer to the exhibit.
Your network uses an MPLS VPN backbone with OSPF routing between all PE and CE routers and on the 10Mb backup Inks between the CE routers. You notice that traffic from CE3 to CE2 and CE4 is flowing over the backup links instead of the higher-bandwidth MPLS VPN backbone even when the
is up.
What change can you make to ensure that traffic uses the MPLS VPN backbone instead?
- A . Configure a 1GB sham link between PE2 and PE4.
- B . Configure a lower cost metric on the provider network’s OSPF-to-BGP redistribution.
- C . Configure internal BGP on PE2, PE3 and PE4.
- D . Configure 1Gb sham links between PE3 and PE4 and between PE3 and PE2.
What is a potential effect of combining TCP traffic and UDP traffic in a single traffic queue?
- A . UDP traffic can start dominating over TCP traffic.
- B . UDP starvation can occur.
- C . This configuration will be rejected as invalid.
- D . TCP and UDP flows would be scheduled fairly.
Which two statements about Cisco HDLC are true? (Choose two)
- A . Cisco HDLC is the preferred protocol in multivendor environments.
- B . Cisco routers can carry multiple network-layer protocols simultaneously over the same HDLC link
- C . Cisco HDLC supports authentication of peering routers on the same HDLC link
- D . Cisco HDLC is the default encapsulation on Serial and Dialer interfaces.
- E . Cisco HDLC allows routers to negotiate the supported network-layer protocols before sending their packets over an HDLC link
- F . Cisco HDLC allows bundling of multiple links between the same pair of routers into a faster communication channel
Refer to the exhibit.
All routers have FULL OSPF adjacencies
Which reason is likely that R3 is missing the 2001:DB8:100:/64 route?
- A . R1 has prefix suppression configured
- B . R1 has an incorrect area number configured
- C . R1 has loop-free alternate routing configured
- D . R1 has LSA throttling configured
Refer to the exhibit.
You notice that neighboring RIP IPv6 routers cannot reach OSPFv3 routes on R1.
Which reason for the problem is most likely true?
- A . The IPv6 RIP process is missing a redistribution route map.
- B . The redistribution command under the OSPF process is missing.
- C . The redistribution metric is too large.
- D . The IPv6 process is missing an IPv6 RIP default metric.
Which interface configuration task enables MLD on the interface?
- A . enabling SSM
- B . setting an IPv6 address
- C . enabling IGMPv3
- D . configuring PIM6
How is the TCAM on a Catalyst switch used when VRF-Lite is configured?
- A . Each configured VRF receives its own Layer 3 TCAM.
- B . Each configured routing protocol receive its own Layer 3 TCAM.
- C . All configured VRFs share the Layer 3 TCAM.
- D . Layer 3 TCAM is not used in VRF-Lite configurations.
Which keychain cryptographic algorithm is supported by the IS-IS routing protocol?
- A . HMAC-SHA1-20
- B . HMAC-SHA1-12
- C . HMAC-MD5
- D . MD5
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