Q1. Which object tracking function tracks the combined states of multiple objects?
A. application
B. interface
C. stub-object
D. list
Answer: D
Q2. Refer to the exhibit.
All switches are Cisco switches. Assume that Cisco Discovery Protocol is enabled only on switches A and C.
Which information is returned when you issue the command show cdp neighbors on switch C?
A. a limited amount of information about switch B
B. no neighbor details will be returned
C. neighbor details for switch B
D. neighbor details for switch A
E. neighbor details for switch C
Answer: B
Explanation:
CDP is used to discover information on directly connected neighbors only, so in this case SwitchC would only be able to obtain CDP information from SwitchB. However, since SwitchB is not running CDP then no neighbor information will be seen on SwitchC. Same goes for Switch A also in this topology.
Q3. Which statement is true about LLDP?
A. LLDP provides VTP support.
B. LLDP does not use a multicast address to communicate.
C. LLDP can indicate only the duplex setting of a link, and not the speed capabilities.
D. LLDP does not support native VLAN indication.
Answer: D
Explanation:
Cisco Discovery Protocol Versus LLDP-MED TLV Comparison
TLV Function
LLDP TLV
Cisco Discovery Protocol TLV
Native VLAN support-Indicates the native VLAN
No
Native VLAN TLV
Reference: http://www.cisco.com/en/US/technologies/tk652/tk701/technologies_white_paper0900aecd 804cd46d.html
Q4. Refer to the exhibit.
Why is the prefix 1.1.1.1/32 not present in the routing table of R1?
A. There is a duplicate router ID.
B. There is a subnet mask mismatch on Ethernet0/0.
C. The router LSA has an invalid checksum.
D. There is an OSPF network type mismatch that causes the advertising router to be unreachable.
Answer: D
Explanation:
A common problem when using Open Shortest Path First (OSPF) is routes in the database don't appear in the routing table. In most cases OSPF finds a discrepancy in the database so it doesn't install the route in the routing table. Often, you can see the Adv Router is not-reachable message (which means that the router advertising the LSA is not reachable through OSPF) on top of the link-state advertisement (LSA) in the database when this problem occurs. Here is an example:
Adv Router is not-reachable
LS agE. 418
Options: (No TOS-capability, DC)
LS TypE. Router
Links Link State ID. 172.16.32.2
Advertising Router: 172.16.32.2
LS Seq Number: 80000002
Checksum: 0xFA63
Length: 60
Number of Links: 3
There are several reasons for this problem, most of which deal with mis-configuration or a broken topology. When the configuration is corrected the OSPF database discrepancy goes away and the routes appear in the routing table.
Reason 1: Network Type Mismatch
Let's use the following network diagram as an example:
R4-4K
R1-7010
interface Loopback0
ip address 172.16.33.1 255.255.255.255
interface Serial2
ip address 172.16.32.1 255.255.255.0
ip ospf network broadcast
router ospf 20
network 172.16.0.0 0.0.255.255 area 0
interface Loopback0
ip address 172.16.30.1 255.255.255.255
!
interface Serial1/0
ip address 172.16.32.2 255.255.255.0
clockrate 64000
router ospf 20
network 172.16.0.0 0.0.255.255 area 0
R4-4K(4)# show ip ospf interface serial 2
Serial2 is up, line protocol is up
Internet Address 172.16.32.1/24, Area 0
Process ID 20, Router ID 172.16.33.1, Network Type BROADCAST, Cost: 64
Transmit Delay is 1 sec, State DR, Priority 1
Designated Router (ID) 172.16.33.1, Interface address 172.16.32.1
Backup Designated router (ID) 172.16.32.2, Interface address 172.16.32.2
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 00:00:08
Neighbor Count is 1, Adjacent neighbor count is 1
Adjacent with neighbor 172.16.32.2 (Backup Designated Router)
Suppress hello for 0 neighbor(s)
R1-7010(5)# show ip ospf interface serial 1/0
Serial1/0 is up, line protocol is up
Internet Address 172.16.32.2/24, Area 0
Process ID 20, Router ID 172.16.32.2, Network Type POINT_TO_POINT, Cost: 64
Transmit Delay is 1 sec, State POINT_TO_POINT,
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 00:00:02
Neighbor Count is 1, Adjacent neighbor count is 1
Adjacent with neighbor 172.16.33.1
Suppress hello for 0 neighbor(s)
As you can see above, Router R4-4K is configured for broadcast, and Router R1-7010 is configured for point-to-point. This kind of network type mismatch makes the advertising router unreachable.
R4-4K(4)# show ip ospf database router 172.16.32.2
Adv Router is not-reachable
LS agE. 418
Options: (No TOS-capability, DC)
LS TypE. Router Links
Link State ID. 172.16.32.2
Advertising Router: 172.16.32.2
LS Seq Number: 80000002
Checksum: 0xFA63
Length: 60
Number of Links: 3
Link connected to: another Router (point-to-point)
(Link ID) Neighboring Router ID. 172.16.33.1
(Link Data) Router Interface address: 172.16.32.2
Number of TOS metrics: 0
TOS 0 Metrics: 64
Link connected to: a Stub Network
(Link ID) Network/subnet number: 172.16.32.0
(Link Data) Network Mask: 255.255.255.0
Number of TOS metrics: 0
TOS 0 Metrics: 64
R1-7010(5)# show ip ospf database router 172.16.33.1
Adv Router is not-reachable
LS agE. 357
Options: (No TOS-capability, DC)
LS TypE. Router Links
Link State ID. 172.16.33.1
Advertising Router: 172.16.33.1
LS Seq Number: 8000000A
Checksum: 0xD4AA
Length: 48
Number of Links: 2
Link connected to: a Transit Network
(Link ID) Designated Router address: 172.16.32.1
(Link Data) Router Interface address: 172.16.32.1
Number of TOS metrics: 0
TOS 0 Metrics: 64
You can see that for subnet 172.16.32.0/24, Router R1-7010 is generating a point-to-point link and Router R4-4K is generating a transit link. This creates a discrepancy in the link-state database, which means no routes are installed in the routing table.
R1-7010(5)# show ip route
172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks
C 172.16.32.0/24 is directly connected, Serial1/0
C 172.16.30.1/32 is directly connected, Loopback0
Solution
To solve this problem, configure both routers for the same network type. You can either change the network type of Router R1-7010 to broadcast, or change Router R4-4K's serial interface to point-to-point.
Reference: http://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/7112-26.html
Q5. Which two statements about BGP prefix-based outbound filtering are true? (Choose two.)
A. It must be configured per address family.
B. It can use prefix lists and route maps for filtering.
C. It can be configured under the global BGP routing process.
D. It can be configured for external peering sessions only.
E. It can increase the processing load on the router.
F. It supports IP multicast routes.
Answer: A,D
Q6. Refer to the exhibit.
Which option explains why the forwarding address is set to 0.0.0.0 instead of 110.100.1.1?
A. The interface Ethernet0/1 is in down state.
B. The next-hop ip address 110.100.1.1 is not directly attached to the redistributing router.
C. The next-hop interface (Ethernet0/1) is specified as part of the static route command; therefore, the forwarding address is always set to 0.0.0.0.
D. OSPF is not enabled on the interface Ethernet0/1.
Answer: D
Explanation:
From the output of the “show ip ospf database” command (although this command is not shown) we can conclude this is an ASBR (with Advertising Router is itself) and E0/1 is the ASBR’s next hop interface for other routers to reach network 192.168.10.0.
The Forwarding Address is determined by these conditions:
* The forwarding address is set to 0.0.0.0 if the ASBR redistributes routes and OSPF is not enabled on the next hop interface for those routes.
* These conditions set the forwarding address field to a non-zero address:
+ OSPF is enabled on the ASBR’s next hop interface AND
+ ASBR’s next hop interface is non-passive under OSPF AND
+ ASBR’s next hop interface is not point-to-point AND
+ ASBR’s next hop interface is not point-to-multipoint AND
+ ASBR’s next hop interface address falls under the network range specified in the router ospf command.
* Any other conditions besides these set the forwarding address to 0.0.0.0.
-> We can see E0/1 interface is not running OSPF because it does not belong to network 110.110.0.0 0.0.255.255 which is declared under OSPF process -> F.A address is set to 0.0.0.0.
Reference: http://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/13682-10.html
Q7. Which two loop-prevention mechanisms are implemented in BGP? (Choose two.)
A. A route with its own AS in the AS_PATH is dropped automatically if the route reenters its own AS.
B. A route with its own cluster ID in the CLUSTER_LIST is dropped automatically when the route reenters its own AS.
C. The command bgp allowas-in enables a route with its own AS_PATH to be dropped when it reenters its own AS.
D. The command bgp bestpath as-path ignore enables the strict checking of AS_PATH so that they drop routes with their own AS in the AS_PATH.
E. The command bgp bestpath med missing-as-worst assigns the smallest possible MED, which directly prevents a loop.
Answer: A,B
Explanation:
When dealing with the possibility of routing updates making their way back into an AS, BGP relies on the information in the AS_path for loop detection. An update that tries to make its way back into the AS it was originated from will be dropped by the border router. With the introduction of route reflectors, there is a potential for having routing loops within an AS. A routing update that leaves a cluster might find its way back inside the cluster. Loops inside the AS cannot be detected by the traditional AS_path approach because the routing updates have not left the AS yet. BGP offers two extra measures for loop avoidance inside an AS when route reflectors are configured.
Using an Originator ID
The originator ID is a 4-byte, optional, nontransitive BGP attribute (type code 9) that is created by the route reflector. This attribute carries the router ID of the originator of the route in the local AS. If, because of poor configuration, the update comes back to the originator, the originator ignores it.
Using a Cluster List
The cluster list is an optional, nontransitive BGP attribute (type code 10). Each cluster is represented with a cluster ID.
A cluster list is a sequence of cluster IDs that an update has traversed. When a route reflector sends a route from its clients to nonclients outside the cluster, it appends the local cluster ID to the cluster list. If the route reflector receives an update whose cluster list contains the local cluster ID, the update is ignored. This is basically the same concept as the AS_path list applied between the clusters inside the AS.
Reference: http://borg.uu3.net/cisco/inter_arch/page11.html
Q8. Which two statements are true about a 6to4 tunnel connecting two IPv6 islands over the IPv4 Internet? (Choose two.)
A. It embeds the IPv6 packet into the IPv4 payload with the protocol type set to 51.
B. It works by appending the private IPv4 address (converted into hexadecimal format) to the 2002::/16 prefix.
C. It embeds the IPv6 packet into the IPv4 payload with the protocol type set to 41.
D. It works by appending the public IPv4 address (converted into hexadecimal format) to the 2002::/16 prefix.
Answer: C,D
Explanation:
6to4 embeds an IPv6 packet in the payload portion of an IPv4 packet with protocol type 41. To send an IPv6 packet over an IPv4 network to a 6to4 destination address, an IPv4
header with protocol type 41 is prepended to the IPv6 packet. The IPv4 destination address for the prepended packet header is derived from the IPv6 destination address of the inner packet (which is in the format of a 6to4 address), by extracting the 32 bits immediately following the IPv6 destination address's 2002::/16 prefix. The IPv4 source address in the prepended packet header is the IPv4 address of the host or router which is sending the packet over IPv4. The resulting IPv4 packet is then routed to its IPv4 destination address just like any other IPv4 packet.
Reference: http://en.wikipedia.org/wiki/6to4
Q9. How many hash buckets does Cisco Express Forwarding use for load balancing?
A. 8
B. 16
C. 24
D. 32
Answer: B
Explanation:
In order to understand how the load balance takes place, you must first see how the tables relate. The Cisco Express Forwarding table points to 16 hash buckets (load share table), which point to the adjacency table for parallel paths. Each packet to be switched is broken up into the source and destination address pair and checked against the loadshare table.
Reference: http://www.cisco.com/c/en/us/support/docs/ip/express-forwarding-cef/18285-loadbal-cef.html
Q10. Which three options are sources from which a SPAN session can copy traffic? (Choose three.)
A. ports
B. EtherChannels
C. VLANs
D. subnets
E. primary IP addresses
F. secondary IP addresses
Answer: A,B,C
Explanation:
. SPAN Sources
The interfaces from which traffic can be monitored are called SPAN sources. Sources designate the traffic to monitor and whether to copy ingress, egress, or both directions of traffic. SPAN sources include the following:
. Ethernet ports
. Port channels
. The inband interface to the control plane CPU — You can monitor the inband interface only from the default VDC. Inband traffic from all VDCs is monitored.
. VLANs — When a VLAN is specified as a SPAN source, all supported interfaces in the VLAN are SPAN sources.
. Remote SPAN (RSPAN) VLANs
. Fabric port channels connected to the Cisco Nexus 2000 Series Fabric Extender .
Satellite ports and host interface port channels on the Cisco Nexus 2000 Series Fabric Extender
— These interfaces are supported in Layer 2 access mode, Layer 2 trunk mode, and Layer 3 mode.
Reference: http://www.cisco.com/c/en/us/td/docs/switches/datacenter/sw/5_x/nx-os/system_management/configuration/guide/sm_nx_os_cg/sm_14span.html#wp1239492