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Q1. Which three routing protocols utilize TLVs? (Choose three.)
A. BGP
B. IS-IS
C. ODR
D. OSPF
E. EIGRP
F. RIP
Answer: A,B,E
Explanation:
IS-IS, originally designed for Open System Interconnection (OSI) routing, uses TLV parameters to carry information in Link State Packets (LSPs). The TLVs make IS-IS extendable. IS-IS can therefore carry different kinds of information in the LSPs. Several routing protocols use TLVs to carry a variety of attributes. Cisco Discovery Protocol (CDP), Label Discovery Protocol (LDP), and Border Gateway Protocol (BGP) are examples of protocols that use TLVs. BGP uses TLVs to carry attributes such as Network Layer Reachability Information (NLRI), Multiple Exit Discriminator (MED), and local pReference: The IP header of the EIGRP packet specifies IP protocol number 88 within it, and the maximum length of the packet will be the IP MTU of the interface on which it is transmitted, most of the time 1500 octets. Following the IP header is the various Type/Length/Value (TLV) triplets. These TLVs will not only carry the route entries but also provide fields for the management of the DUAL process, multicast sequencing, and IOS software versions from the router.
References: http://www.cisco.com/c/en/us/support/docs/ip/integrated-intermediate-system-to-intermediate-system-is-is/5739-tlvs-5739.html http://ericleahy.com/index.php/eigrp-packets-neighborships/
Q2. Which two statements about SNMP are true? (Choose two.)
A. SNMPv3 provides privacy and access control.
B. All SNMP versions use get, getNext, and getBulk operations.
C. SNMPv3 uses encrypted community strings.
D. SNMPv1 and SNMPv2c use plaintext community strings.
E. All SNMP versions support bulk retrieval and detailed error messages.
Answer: A,B
Q3. Refer to the exhibit.
Which IP packets will be accepted from EBGP neighbor 10.1.1.1?
A. IP packets with a TTL count in the header that is equal to or greater than 253
B. IP packets with a TTL count in the header that is equal to 253
C. IP packets with a TTL count in the header that is equal to or greater than 2
D. IP packets with a TTL count in the header that is equal to 2
Answer: A
Explanation:
neighbor ip-address ttl-security hops hop-count
ExamplE.
Router(config-router)# neighbor 10.1.1.1 ttl-security hops 2
Configures the maximum number of hops that separate two peers.
. The hop-count argument is set to number of hops that separate the local and remote peer.
If the expected TTL value in the IP packet header is 254, then the number 1 should be configured for the hop-count argument. The range of values is a number from 1 to 254.
. When this feature is enabled, BGP will accept incoming IP packets with a TTL value that is
equal to or greater than the expected TTL value. Packets that are not accepted are silently discarded.
. The example configuration sets the expected incoming TTL value to at least 253, which is 255 minus the TTL value of 2, and this is the minimum TTL value expected from the BGP peer. The local router will accept the peering session from the 10.1.1.1 neighbor only if it is 1 or 2 hops away.
Reference: http://www.cisco.com/c/en/us/td/docs/ios/12_2s/feature/guide/fs_btsh.html
Q4. Which two statements about the BGP community attribute are true? (Choose two.)
A. Routers send the community attribute to all BGP neighbors automatically.
B. A router can change a received community attribute before advertising it to peers.
C. It is a well-known, discretionary BGP attribute.
D. It is an optional transitive BGP attribute.
E. A prefix can support only one community attribute.
Answer: B,D
Explanation:
A community is a group of prefixes that share some common property and can be configured with the BGP community attribute. The BGP Community attribute is an optional transitive attribute of variable length. The attribute consists of a set of four octet values that specify a community. The community attribute values are encoded with an Autonomous System (AS) number in the first two octets, with the remaining two octets defined by the AS. A prefix can have more than one community attribute. A BGP speaker that sees multiple community attributes in a prefix can act based on one, some or all the attributes. A router has the option to add or modify a community attribute before the router passes the attribute on to other peers.
Reference:
http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/28784-bgp-community.html
Q5. DRAG DROP
Drag and drop the OTV component on the left to the function it performs on the right.
Answer:
Q6. Which statement about passive interfaces is true?
A. The interface with the OSPF passive interface configuration appears as a not-so-stubby network.
B. The interface with the EIGRP passive interface configuration ignores routes after the exchange of hello packets.
C. The interface with the IS-IS passive interface configuration sends the IP address of that interface in the link-state protocol data units.
D. Passive interface can be configured on the interface for IS-IS.
Answer: C
Explanation:
With IS-IS, passive interfaces are used to prevent unnecessary LSA packets out that interface, but the IP address of passive interfaces are still included in updates going out the other interfaces. This behavior is what enables the best practice of configuring loopback interfaces as passive, but still having the loopback be reachable.
Q7. In which way does the Bridge Assurance mechanism modify the default spanning-tree behavior in an effort to prevent bridging loops?
A. Received BPDUs are looped back toward the sender to ensure that the link is bidirectional.
B. If BPDUs are no longer received on a port, the switch immediately sends out a TCN BPDU.
C. Extended topology information is encoded into all BPDUs.
D. BPDUs are sent bidirectional on all active network ports, including blocked and alternate ports.
Answer: D
Q8. Which statement about MSS is true?
A. It is negotiated between sender and receiver.
B. It is sent in all TCP packets.
C. It is 20 bytes lower than MTU by default.
D. It is sent in SYN packets.
E. It is 28 bytes lower than MTU by default.
Answer: D
Explanation:
The maximum segment size (MSS) is a parameter of the Options field of the TCP header that specifies the largest amount of data, specified in octets, that a computer or communications device can receive in a single TCP segment. It does not count the TCP header or the IP header. The IP datagram containing a TCP segment may be self-contained within a single packet, or it may be reconstructed from several fragmented pieces; either way, the MSS limit applies to the total amount of data contained in the final, reconstructed TCP segment. The default TCP Maximum Segment Size is 536. Where a host wishes to set the maximum segment size to a value other than the default, the maximum segment size is specified as a TCP option, initially in the TCP SYN packet during the TCP handshake. The value cannot be changed after the connection is established.
Reference: http://en.wikipedia.org/wiki/Maximum_segment_size
Q9. How does MSTP provide backward compatibility with RSTP?
A. It uses the hop count variable as a TTL counter.
B. It transmits all spanning-tree information in one BPDU.
C. It supports up to 128 MSTI messages.
D. It encodes the MSTP-specific region information before the legacy RSTP BPDU.
Answer: D
Q10. When BGP route reflectors are used, which attribute ensures that a routing loop is not created?
A. weight
B. local preference
C. multiexit discriminator
D. originator ID
Answer: D
Explanation:
As the iBGP learned routes are reflected, routing information may loop. The route reflector model has the following mechanisms to avoid routing loops:
. Originator ID is an optional, nontransitive BGP attribute. It is a 4-byte attributed created by a route reflector. The attribute carries the router ID of the originator of the route in the local autonomous system. Therefore, if a misconfiguration causes routing information to come back to the originator, the information is ignored.
. Cluster-list is an optional, nontransitive BGP attribute. It is a sequence of cluster IDs that the route has passed. When a route reflector reflects a route from its clients to nonclient peers, and vice versa, it appends the local cluster ID to the cluster-list. If the cluster-list is empty, a new cluster-list is created. Using this attribute, a route reflector can identify if routing information is looped back to the same cluster due to misconfiguration. If the local cluster ID is found in the cluster-list, the advertisement is ignored.
Reference: http://www.cisco.com/c/en/us/td/docs/ios/12_2/ip/configuration/guide/fipr_c/1cfbgp.html