642-813 Q&A – Implement High Availability (11-15)

Section 5 – Implement High Availability, given a network design and a set of requirements

QUESTION NO: 11
On a 3550 EMI switch, which three types of interfaces can be used to configure HSRP? (Choose three.)
A.loopback interface
B.SVI interface
C.routed port
D.access port
E.EtherChannel port channel
F.BVI interface
Answer: B C E

Explanation:
This Hot Standby Router Protocol (HSRP) provides routing redundancy for routing IP traffic without being dependent on the availability of any single router. To use this feature, you must have the enhanced multilayer software image installed on your switch. All Catalyst 3550 Gigabit Ethernet switches ship with the enhanced multilayer software image (EMI) installed. Catalyst 3550
Fast Ethernet switches can be shipped with either the standard multilayer software image (SMI) or EMI pre-installed. You can order the Enhanced Multilayer Software Image Upgrade kit to upgrade Catalyst 3550 Fast Ethernet switches from the SMI to the EMI.
Only routed interfaces that provide access to hosts can be configured for HSRP. These interfaces include: routed Ethernet, routed fast Ethernet, routed Gigabit Ethernet, SVI, and EtherChannel.

QUESTION NO: 12
Refer to the exhibit. Based upon the debug output that is shown, which three statements about HSRP are true? (Choose three.)

A.The final active router is the router with IP address 172.16.11.111.
B.The router with IP address 172.16.11.111 has preempt configured.
C.The priority of the router with IP address 172.16.11.112 is preferred over the router with IP address 172.16.11.111.
D.The IP address 172.16.11.115 is the virtual HSRP IP address.
E.The router with IP address 172.16.11.112 has nonpreempt configured.
F.The router with IP address 172.16.11.112 is using default HSRP priority.
Answer: A B D
Explanation:
Each router in an HSRP group has its own unique IP address assigned to an interface. This address is used for all routing protocol and management traffic initiated by or destined to the router. In addition, each router has a common gateway IP address, the virtual router address, that is kept alive by HSRP. This address is also referred to as the HSRP address or the standby address . Clients can point to that virtual router address as their default gateway, knowing that a router always keeps that address active. Keep in mind that the actual interface address and the virtual (standby) address must be configured to be in the same IP subnet. You can assign the HSRP address with the following interface command:

Switch(config-if)# standby group ip ip-address [secondary]

When HSRP is used on an interface that has secondary IP addresses, you can add the secondary keyword so that HSRP can provide a redundant secondary gateway address.
You can configure a router to preempt or immediately take over the active role if its priority is the highest at any time. Use the following interface configuration command to allow preemption:
Switch( config-if)# standby group preempt [delay seconds]
By default, the router can preempt another immediately, without delay. You can use the delay keyword to force it to wait for seconds before becoming active. This is usually done if there are routing protocols that need time to converge.

QUESTION NO: 13
Which router redundancy protocol cannot be configured for interface tracking?
A. HSRP
B. GLBP
C. VRRP
D. SLB
E. RPR
F. RPR+
Answer: C
Explanation:
The Virtual Router Redundancy Protocol (VRRP) is a standards-based alternative to HSRP, defined in IETF standard RFC 2338. VRRP is so similar to HSRP that you need to learn only slightly different terminology and a couple of slight functional differences. VRRP provides one redundant gateway address from a group of routers. The active router is called the master router , while all others are in the backup state . The master router is the one with the highest router priority in the VRRP group. VRRP group numbers range from 0 to 255; router priorities range from 1 to 254 (254 is the highest; 100 is the default). The virtual router MAC address is of the form 0000.5e00.01 xx , where xx is a two-digit hex VRRP group number. VRRP advertisements are sent at 1-second intervals. Backup routers can optionally learn the advertisement interval from the master router. By default, all VRRP routers are configured to preempt the current master router, if their priorities are greater. VRRP has no mechanism for tracking interfaces to allow more capable routers to take over the master role.

QUESTION NO: 14
Refer to the exhibit. Based on the debug standby output in the exhibit, which HSRP statement is true?

A. DSW111 is the active router because it is the only HRSP-enabled router on that segment.
B. DSW111 is the active router because the standby timer has been incorrectly configured.
C. DSW111 is the active router because it has a lower priority on that VLAN.
D. DSW111 is the active router because it has a lower IP address than the tying priority router on that VLAN.
E. DSW111 is the active router and is advertising the virtual IP address 10.10.10.111 on VLAN 11.
Answer: A
Explanation:
In the output shown, it can be seen that the standby router is unknown, and the active timer is expired meaning that this router was unable to locate any other HSRP enabled routers on the LAN. It then became the active router, with no standby router.

QUESTION NO: 15
You have configured router R1 with HSRP, using the standard defaults. Which three statements are true of a default HSRP configuration? (Select three)
A. The Standby hello time is 2 seconds.
B. Two HSRP groups are configured.
C. The Standby track interface priority is 10.
D. The Standby hold time is 10 seconds
E. The Standby priority is 100.
F. The Standby delay is 3 seconds.
Answer: CDE
Explanation:
HSRP uses a priority scheme to determine which HSRP-configured router is to be the default active router. To configure a router as the active router, you assign it a priority that is higher than the priority of all the other HSRP-configured routers. The default priority is 100, so if you configure just one router to have a higher priority, that router will be the default active router.
For both HSRP and MHSRP, you can use the tracking feature to adjust the Hot Standby priority of a router based on whether certain of the router’s interfaces are available. When a tracked interface becomes unavailable, the HSRP priority of the router is decreased. The default decrement value is 10.
The standby timers interface configuration command sets the interval in seconds between hello messages (called the hello time ) to five seconds and sets the duration in seconds that a router waits before it declares the active router to be down (called the hold time ) to eight seconds. (The defaults are three and 10 seconds, respectively.) If you decide to modify the default values, you must configure each router to use the same hello time and hold time.