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642-813 Q&A – Implement High Availability (41-45)

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

Which statement best describes Cisco supervisor engine redundancy using Stateful Switchover?
A. Redundancy provides fast supervisor switchover for all Cisco Catalyst 6500 series switches.
B. Switchover ensures that Layer 2 through Layer 4 traffic is not interrupted.
C. Switchover can be caused by clock synchronization failure between supervisors.
D. Redundancy requires BGP, OSPF, EIGRP, or IS-IS.
Answer: C

What multicast address is used by GLBP?
Answer: E
The Gateway Load Balancing Protocol feature provides automatic router backup for IP hosts configured with a single default gateway on an IEEE 802.3 LAN. GLBP members communicate between each other through hello messages sent every 3 seconds to the multicast address, User Datagram Protocol (UDP) port 3222 (source and destination).

Which protocol specified by RFC 2281 provides network redundancy for IP networks, ensuring that user traffic immediately and transparently recovers from first-hop failures in network edge devices or access circuits?
Answer: D
HSRP is a Cisco-proprietary protocol developed to allow several routers (or multilayer switches) to appear as a single gateway address. RFC 2281 describes this protocol in more detail. Basically, each of the routers that provides redundancy for a given gateway address is assigned to a common HSRP group. One router is elected as the primary, or active, HSRP router, another is elected as the standby HSRP router, and all the others remain in the listen HSRP state. The routers exchange HSRP hello messages at regular intervals, so they can remain aware of each other’s existence, as well as that of the active router.
An HSRP group can be assigned an arbitrary group number, from 0 to 255. If you configure HSRP groups on several VLAN interfaces, it can be handy to make the group number the same as the VLAN number. However, most Catalyst switches support only up to 16 unique HSRP group numbers. If you have more than 16 VLANs, you will quickly run out of group numbers. An alternative is to make the group number the same (that is, 1) for every VLAN interface. This is perfectly valid because the HSRP groups are only locally significant on an interface. HSRP Group 1 on interface VLAN 10 is unique from HSRP Group 1 on interface VLAN 11.

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
B.The router with IP address has preempt configured.
C.The priority of the router with IP address is preferred over the router with IP address
D.The IP address is the virtual HSRP IP address.
E.The router with IP address has nonpreempt configured.
F.The router with IP address is using default HSRP priority.
Answer: A B D
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.

In the hardware address 0000.0c07.ac0av, what does 07.ac represent?
A. HSRP well-known physical MAC address
B. Vendor code
C. HSRP router number
D. HSRP group number
E. HSRP well-known virtual MAC address
Answer: E
HSRP code (HSRP well-known virtual MAC address) – The fact that the MAC address is for an HSRP virtual router is indicated in the next two bytes of the address. The HSRP code is always 07.ac. The HSRP protocol uses a virtual MAC address, which always contains the 07.ac numerical value.

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