Cisco (300-410-ENARSI) Exam Questions And Answers page 26

The correct answer is to use the tunnel mode ipv6ip 6to4 command to complete the configuration of an automatic 6-to-4 tunnel. This command requires the use of IPv6 unicast addresses that have the 2002::/16 prefix.
The types of tunneling mechanisms supported by IPv6 are:
• Automatic 6-to-4 tunnel
• ISATAP tunnel
• Manually configured tunnel
• GRE tunnel
Apart from using a tunneling mechanism, interoperability between IPv4 and IPv6 can be provided by using a dual-stack infrastructure or Network Address Translation-Protocol Translation (NAT-PT). A dual-stack infrastructure allows you to use both IPv4 and IPv6 addresses on the same router/host. NAT-PT is used to translate IPv4 addresses to IPv6 and vice versa.
The tunnel mode ipv6ip command should not be used to complete the configuration because this command specifies IPv6 as the passenger protocol and creates a manually configured tunnel.
The tunnel mode ipv6ip auto-tunnel command is not required to enable automatic 6-to-4 tunneling on the border routers. This command creates an automatic IPv4-compatible IPv6 tunnel between the routers.
The tunnel mode ipv6ip isatap command should not be used because this command creates an ISATAP tunnel.
Objective:
Network Principles
Sub-Objective:
Recognize proposed changes to the network
Cisco IOS IPv6 Configuration Guide; Implementing Tunneling for IPv6 > Configuring Manual IPv6 Tunnels
Cisco > Cisco IOS IPv6 Command Reference > tunnel mode ipv6ip

The effect of the passive-interface command is dependent on the routing protocol. With RIP, the command prevents the sending of route updates, but does not prevent the reception of route updates. With EIGRP, the passive-interface command prevents both the sending and receiving of route updates, and also the sending of hellos. Without hello packets, the routers are unable to maintain the neighbor relationship, upon which all communications including route updates depend.
If the intent was to preventing routing updates from Router 1 to Router 2 while still allowing updates from Router 2 to Router 1, the routing updates must be filtered out and denied on Router 1 with a distribute list, as shown in the following command set:
router1(config)access-list 101 deny any
router1(config)#router eigrp 100
router1(config-router)distribute-list 101 out

Objective:
Layer 3 Technologies
Sub-Objective:
Troubleshoot passive interfaces
Cisco IOS Master Command List, Release 12.4T > p through r > passive-interface
Cisco > Home > Support > Technology Support > IP > IP Routing > Design > Design Technotes > Filtering Routing Updates on Distance Vector IP Routing Protocols

The problem is that the metric was not configured. Some routing protocols require that a metric be provided for the redistributed routing protocol or route redistribution will not occur successfully. RIP and EIGRP both require that a metric be provided. IS-IS and OSPF do not have this requirement.
When you redistribute traffic into EIGRP without specifying a metric, then the default metric applied is zero, the route will be treated as unreachable, and the route will not be advertised. The addition of the metric parameter as shown below would solve this issue:
Router9(config)# router eigrp 100
Router9(config-router)# redistribute ospf 20 metric 10000 100 255 1 1500

In this example, 1000 is the bandwidth, 100 is the delay, 255 is the reliability, 1 is the load, and 1500 is the MTU.
The process IDs are correct in the original scenario, and the command was executed in the correct context.
Objective:
Layer 3 Technologies
Sub-Objective:
Configure and verify redistribution between any routing protocols or routing sources
Cisco > Home > Support > Technology Support > IP > IP Version 6 > Configure > Configuration Examples and Technotes > Redistributing Routing Protocols

This behavior is caused by asymmetric routing. This is quite common in a routed network and usually is not a problem. It can, however, become an issue when firewalls reside in a routed path. Firewalls can cause problems when they maintain state information about connections. State information is used to determine if return connection is allowed. If the return path is routed through a different firewall, it will not have the correct state information for the connection, and the return will be disallowed.
It is not caused by windowing. This is a technique used to adjust the number of packets that can be acknowledged at once by a receiving computer in a transmission. In times of congestion, the window or number of packets that can be acknowledged at a time will be small. Later, when congestion goes down, the window size can be increased.
The behavior is not caused by the maximum segment size (MSS). This value specifies the largest amount of data, in octets, that a computer or communications device can receive in a single TCP segment. This will not cause a packet to take a different path in the return than it did on its way to the destination.
The behavior is not caused by global synchronization. This occurs when congestion on the network causes all devices to reduce their transmission rates at the same time. The result is the network cycling between sharp increases and sharp decreases in traffic.
Objective:
Network Principles
Sub-Objective:
Explain TCP operations
Home > Services > Technical services newsletter > Tech insights > Chalk talk > Asymmetric Routing and Firewalls

The two commands that must have been executed to produce output in that format are logging console level notifications and service timestamps log datetime msec.
The logging console level notifications command species that all messages at level 5 (notifications and above) will be sent to the console. This is not entered by the number of the message type, but the name of the message type.
The service timestamps log datetime msec command specifies that a timestamp up to the millisecond should be included in all messages that include the time.
While the logging console level command can be used with a level number on some devices, notifications are level 5, not 4.
The service timestamps log datetime command specifies that a timestamp should be included in all messages, but it will not include the millisecond. Better logging functionality can be achieved by using the msec keyword to help organize tightly spaced events.
The logging history command can specify the proper level of messages to reduce unnecessary messages.
Objective:
Infrastructure Services
Sub-Objective:
Configure and verify logging
Catalyst 2960 and 2960-S Software Configuration Guide, 12.2(55)SE > Configuring System Message Logging
Cisco > Cisco IOS Embedded Syslog Manager Command Reference > logging console
Cisco > Cisco IOS Configuration Fundamentals Command Reference > R through setup > service timestamps

The given set of commands creates a static default route on RouterA and redistributes this route into the EIGRP company network. The ip route 0.0.0.0 0.0.0.0 S0/0 command executed in the global configuration mode creates a static default route on the router. The ip route command allows you to specify a static route. The redistribute static metric 1000 1 255 1 1500 command then redistributes the static default route into the EIGRP autonomous system (AS) 200. This implies that the EIGRP network identifies the default route as an external route, and traffic to all unknown destination subnets will be diverted to the default route.
Alternatively, default routes can be advertised into EIGRP networks by either of the following methods:
• Using the network 0.0.0.0 command on the router
• Using the ip summary-address eigrp 200 0.0.0.0 0.0.0.0 command on the router
A summary default route is not created on RouterA in the scenario. If the ip summary-address eigrp 200 0.0.0.0 0.0.0.0 command was used on RouterA, then a summary default route would be created. The summary default route points to the 0.0.0.0 network with the null0 interface as the next-hop interface. Summary default routes are helpful for providing remote networks with a default route.
The default route is advertised to the EIGRP network because the redistribute command was executed. This command is used to advertise the default route to the EIGRP network.
Objective:
Layer 3 Technologies
Sub-Objective:
Configure and verify default routing
Cisco > Support > Technology Support > IP > IP Routing > Design > Design TechNotes > Configuring a Gateway of Last Resort Using IP Commands
Cisco > Support > Technology Support > IP > IP Routing > Technology Information > Technology White Paper > Enhanced Interior Gateway Routing Protocol

The eigrp router-id command should be executed in router configuration mode to fix the issue. This command specifies a fixed router IPv4 address to the router. If this command is missing or incorrectly configured on the router, EIGRP for IPv6 will not run properly.
Another command that you should perform so that EIGRP for IPv6 runs on the routers is the no shutdown command. You should execute this command in interface configuration mode. The no shutdown command is necessary because all the interfaces with EIGRP for IPv6 enabled on them are in a shutdown state by default.
A sample configuration to implement EIGRP for IPv6 on a router is as follows:
rtrA(config)# ipv6 unicast-routing
rtrA(config) # interface Fa0/1
rtrA(config-if) # ipv6 enable
rtrA(config-if) # ipv6 eigrp 355
rtrA(config-if)# no shutdown
rtrA(config-if) # exit
rtrA(config)# ipv6 router eigrp 355
rtrA(config-rtr)# eigrp router-id 1.1.1.1

The two options stating that the ipv6 address command should be executed on the routers are incorrect. EIGRP for IPv6 can be configured on router interfaces without explicitly specifying a global unicast IPv6 address. If you specify the ipv6 enable command, as in this scenario, then the ipv6 address command is not required.
The option stating that the eigrp router-id command should be executed in interface configuration mode is incorrect. This command should be executed in router configuration mode instead of interface or global configuration modes.
Objective:
Layer 3 Technologies
Sub-Objective:
Identify IPv6 addressing and subnetting
Cisco IPv6 Implementation Guide, Release 15.2M&T > Implementing EIGRP for IPv6 > How to Implement EIGRP for IPv6 > Enabling EIGRP for IPv6 on an Interface

The following command sequence is correct:
Router1(config)# service dhcp
Router1(config)# ip dhcp pool IPPool
Router1(dhcp-config)# network 10.10.0.0 255.255.0.0
Router1(dhcp-config)# domain-name Cisco
Router1(dhcp-config)# dns-server 10.10.0.1
Router1(dhcp-config)# default-router 10.10.0.1
Router1(dhcp-config)# exit
Router1(config)# ip dhcp excluded-address 10.10.0.20 10.10.0.25
The Router1(config)# service dhcp command enables the DHCP process. It is enabled by default, but this command may be needed if it has been disabled.
The Router1(config)# ip dhcp pool IPPool command creates a DHCP pool named IPPool.
The Router1(dhcp-config)# network 10.10.0.0 255.255.0.0 command specifies the subnet and mask for which the DHCP process will be handing out IP addresses. Unless otherwise specified, it is assumed that the assignment will start with the first address on the subnet and end with the last address on the subnet; in this case, 10.10.0.1 through 10.10.0.255.
The Router1(dhcp-config)# domain-name Cisco command sets the domain name for the clients to "Cisco."
The Router1(dhcp-config)# dns-server 10.10.0.1 command sets the DNS server IP address for the clients to 10.10.0.1.
The Router1(dhcp-config)# default-router 10.10.0.1 command sets the default gateway for the clients to 10.10.0.1.
The Router1(dhcp-config)# exit command exits back to global config mode.
The Router1(config)# ip dhcp excluded-address 10.10.0.20 10.10.0.25 command configures the DHCP process not to hand out addresses 10.10.0.20 through 10.10.0.25 so that there is no conflict with the print servers. This command is technically not a dhcp-config command, but if it is issued in the dhcp-config mode, the router will exit to global config mode and invoke the command.
The other options are incorrect due to incorrect syntax or command mode.
Objective:
Infrastructure Services
Sub-Objective:
Configure and verify IPv4 and IPv6 DHCP
Cisco > Cisco IOS IP Addressing Services Configuration Guide, Release 12.4 > Part 3: DHCP > DHCP Overview

The following command set would NOT be used because it only applies the access list route-map change_parameters inbound instead of outbound, as would be required:

The ACL 1 allows the 192.168.58.0/24 and the 192.168.127.0/24 subnets, while the ACL 2 allows the 172.161.94.0/24 subnet. The neighbor route-map command specifies a route-map named change_parameters for the 201.60.3.1 BGP peer. The out keyword at the end of the command indicates that the route-map is applied only to the updates sent by rtrB, and not received by rtrB.
In the following command, the route map change_parameters is defined with the permit keyword. The permit keyword indicates that if a match occurs, the actions specified in the set sub-command are executed:
route-map change_parameters permit 10
match ip-address 2
set metric 500
In this case, this command checks if the IP address of the subnets advertised to rtrA is in the 172.161.94.0/24 subnet (specified by ACL 2). If the IP address matches, then the metric of those routes are set to 500.
In the following command, the route map change_parameters is defined with the permit keyword:
route-map change_parameters permit 20
match ip-address 1
set metric 300
In this case, this command checks if the IP address of the subnets advertised to rtrA is in the 192.168.58.0/24 or the 192.168.127.0/24 subnets (specified by ACL 1) If the IP address matches, then the metric of those routes are set to 300.
Objective:
Layer 3 Technologies
Sub-Objective:
Configure and verify eBGP (IPv4 and IPv6 address families)
Cisco > Home > Support > Technology Support > IP > IP Routing > Design > Design Technotes > BGP Case Studies > Route Maps
Cisco > Cisco IOS IP Routing: Protocol-Independent Command Reference > route-map

The FE80::260:3EFF:FE11:6770/10 address can be assigned to an interface of the IPv6-enabled router. This address is a link-local address as it has the prefix FE80::/10. Link-local addresses can be configured for an interface either automatically or manually.
Link-local addresses are IPv6 unicast addresses that are configured on the interfaces of an IPv6-enabled router. With link-local addresses, the nodes can connect to a network (local link) and communicate with other nodes. In addition, these addresses participate in the neighbor discovery protocol and the stateless auto-configuration process.
The FEC0:0:0:1::1/64 address should not be used for the interfaces because this address is a site-local address. Site-local addresses are IPv6 equivalent addresses to IPv4's private address classes. These addresses are available only within a site or an intranet, which typically is made of several network links.
You should not use the 2001:0410:0:1:0:0:0:1/64 and 2002:500E:2301:1:20D:BDFF:FE99:F559 addresses for the interfaces. These two addresses are global unicast addresses as they fall in the range from 2000::/3 and to E000::/3. A global address is used on links that connect organizations to the Internet service providers (ISPs).
Objective:
Layer 3 Technologies
Sub-Objective:
Identify IPv6 addressing and subnetting
Cisco > Understanding IPv6 Link Local Address