Home » SWITCH 642-813 Q&As » Section 5 - High Availability » 642-813 Q&A – Implement High Availability (26-30)

642-813 Q&A – Implement High Availability (26-30)

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

QUESTION NO: 26
Refer to the exhibit. Both routers are configured for the Gateway Load Balancing Protocol (GLBP). Which statement is true?

28

In this network segment, the two routers on the network are configured for GLBP (Gateway Load Balancing Protocol). What can be said about this?
A. The hosts will have different default gateway IP addresses and different MAC addresses for each rtouter. B. The default gateway address of each host should be set to the virtual IP address.
C. The hosts will learn the proper default gateway IP address from Router Pass4sure1.
D. The default gateway address of each host should be set to the real IP address of the router.
Answer: B
Explanation:
GLBP performs a similar, but not identical, function for the user as the HSRP and VRRP. Both HSRP and VRRP protocols allow multiple routers to participate in a virtual router group configured with a virtual IP address. One member is elected to be the active router to forward packets sent to the virtual IP address for the group. The other routers in the group are redundant until the active router fails. With standard HSRP and VRRP, these standby routers pass no traffic in normal operation – which is wasteful. Therefore the concept cam about for using multiple virtual router groups, which are configured for the same set of routers. But to share the load, the hosts must be configured for different default gateways, which results in an extra administrative burden of going around and configuring every host and creating 2 or more groups of hosts that each use a different default gateway.
GLBP is similar in that it provides load balancing over multiple routers (gateways) – but it can do this using only ONE virtual IP address!!! Underneath that one virtual IP address is multiple virtual MAC addresses, and this is how the load is balanced between the routers. Instead of the hassle of configuring all the hosts with a static Default Gateway, you can lket them use ARP’s to find their own. Multiple gateways in a “GLBP redundancy group” respond to client Address Resolution Protocol (ARP) requests in a shared and ordered fashion, each with their own unique virtual MAC addresses. As such, workstation traffic is divided across all possible gateways. Each host is configured with the same virtual IP address, and all routers in the virtual router group participate in forwarding packets.

QUESTION NO: 27
Refer to the exhibit. Which three statements accurately describe this GLBP topology? (Choose three.)

26
A. Router A is responsible for answering ARP requests sent to the virtual IP address.
B. If Router A becomes unavailable, Router B will forward packets sent to the virtual MAC address of Router A.
C. Router A alternately responds to ARP requests with different virtual MAC addresses.
D. Router B will transition from blocking state to forwarding state when it becomes the AVG.
E. If another router were added to this GLBP group, there would be two backup AVGs.
F. Router B is in GLBP listen state.
Answer: A,B,C
Explanation:
With GLBP the following is true:
With GLBP, there is 1 AVG and 1 standby VG. In this case Company1 is the AVG and Company2 is the standby. Company2 would act as a VRF and would already be forwarding and routing packets. Any additional routers would be in a listen state.
As the role of the Active VG and load balancing, Company1 responds to ARP requests with different virtual MAC addresses.
In this scenario, Company2 is the Standby VFfor the VMAC 0008.b400.0101 and would become the Active VF if Company1 were down.
As the role of the Active VG, the primary responsibility is to answer ARP requests to the virtual IP address.
As an AVF router Company2 is already forwarding/routing packets

QUESTION NO: 28
Refer to the exhibit. What statement is true based upon the configuration of router R1 and router R2?

27
A.Router R1 will become the active virtual gateway.
B.Router R2 will become the active virtual gateway.
C.The hello and hold timers are incompatible with multi-homed BGP.
D.The hello and hold timers are incompatible with OSPF type 5 LSAs.
E.Router R1 will become the master for Virtual Router 1, and router R2 will become the backup for Virtual Router 2.
F.Router R2 will become the master for Virtual Router 1, and router R1 will become the backup for Virtual Router 2.
Answer: A
Explanation:
GLBP gateway priority determines the role that each GLBP gateway plays and what happens if the AVG fails.
Priority also determines if a GLBP router functions as a backup virtual gateway and the order of ascendancy to becoming an AVG if the current AVG fails. You can configure the priority of each backup virtual gateway with a value of 1 through 255 using the glbp priority command. The default priority value is 100. In this case, since router Company1 has a configured priority of 150, it will become the active gateway.

QUESTION NO: 29
Refer to the exhibit. Host A has sent an ARP message to the default gateway IP address
10.10.10.1. Which statement is true?

29
A. DSw2 will reply with the IP address of the next AVF.
B. DSw1 will reply with the MAC address of the next AVF.
C. Because of the invalid timers that are configured, DSw1 will not reply.
D. DSw1 will reply with the IP address of the next AVF.
E. Because of the invalid timers that are configured, DSw2 will not reply.
F. DSw2 will reply with the MAC address of the next AVF.
Answer: F
Explanation:
The Gateway Load Balancing Protocol (GLBP) is a Cisco-proprietary protocol designed to overcome the limitations of existing redundant router protocols. Some of the concepts are the same as with HSRP/VRRP, but the terminology is different and the behavior is much more dynamic and robust.
The trick behind this load balancing lies in the GLBP group. One router is elected the active virtual gateway (AVG). This router has the highest priority value, or the highest IP address in the group, if there is no highest priority. The AVG answers all ARP requests for the virtual router address.
Which MAC address it returns depends on which load-balancing algorithm it is configured to use.
In any event, the virtual MAC address supported by one of the routers in the group is returned.
According to exhibit, Router Company2 is the Active Virtual Gateway (AVG) router because it has highest IP address even having equal priority. When router Company1 sends the ARP message to 10.10.10.1 Router Company2 will reply to Company1 as a Active Virtual Router.

QUESTION NO: 30
Which command will need to be added to External_A to ensure that it will take over if serial 0/0 on External_B fails?

30
A. standby 1 preempt
B. standby 1 track 10.10.10.1
C. standby 1 priority 130
D. standby 1 track fastethernet 0/0
Answer: A
Explanation:
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

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