Understand and implement: GLBP (new test site for ccna200-120)

Understanding and implementation: new test site for GLBPccna200-120)

GLBPGateway Load Balancing Protocol) The Gateway Load Balancing Protocol, which belongs to Cisco and is more advanced than HSRP and VRRP in terms of redundancy and Load Balancing, simply put, multiple available gateway routers are automatically selected and used at the same time, and can be switched to the redundant path in case of a fault to make full use of resources. HSRP and VRRP cannot achieve this. To support load balancing in HSRP and VRRP, you must configure and manage multiple heat capacity groups. But GLBP does not. However, GLBP has limits. It can only support collaboration between up to four routers.

To successfully understand GLBP, you must clarify the following knowledge objectives:

Ü GLBP virtual MAC formation and allocation methods

Ü GLBP role

Ü GLBP load balancing method

Understanding the form and allocation of GLBP virtual MAC

The virtual IP addresses in HSRP and VRRP correspond to the same virtual MAC. In GLBP, to achieve automatic load balancing, its virtual IP addresses correspond to multiple virtual MAC addresses, as shown in figure 9.133, if host A forwards data through R1 during Automatic Server Load balancer, host A receives the MAC address of 192.168.2.100 as 2.16.0000.0001; host B forwards data through R2, host B will get the MAC corresponding to 192.168.2.100 as 2.16.0000.0002; of course, both MAC are virtual. The question that needs to be further considered is: Since GLBP generates different virtual MAC addresses for different senders, What Is ARP request and sending during communication, who uses these different virtual MAC for ARP response?

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Understand the role of GLBP

There are two roles in GLBP: activevirtual gateway (vroactive), also known as AVG, and activevirtual forworders (also known as AVF). As shown in Figure 9.134, AVG is responsible for determining who will forward the traffic in the GLBP group and uniformly responding to the MAC address of the virtual IP address 192.168.2.100 requested by the client. How does AVG determine who will forward the traffic, how to uniformly respond to ARP for the client? These two processes complement each other.

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Specifically, AVG is responsible for determining who will forward the traffic in the GLBP group, which is determined by the GLBP load balancing method. Different Load Balancing methods will be described later, when the AVG determines who will forward the traffic, the gateway used for traffic Forwarding is called an active forwarder, that is, AVF. Of course, the client can only see one default gateway IP address, that is, the GLBP virtual IP address, which is 192.168.2.100 in this instance. Then the client will request the MAC address corresponding to 192.168.2.100, at this time, AVG will use the virtual MAC of the AVF to complete ARP response after a certain AVF forwards traffic. Note that the client's ARP request will be uniformly responded by AVG, the AVF does not respond to the forwarded traffic, so AVG wants to be the manager in the GLBP group. Generally, in a GLBP group, a vro is both AVG and AVF, and other vrouters in the group are AVF. Since AVG is so important, who in the GLBP group will be AVG?

Who will be the AVG gateway in the GLBP group?

A router with a high GLBP priority will become AVG. By default, the GLBP priority is 100. If the priority is the same, the router with a high IP address on the physical interface will become AVG, it is not hard to see that this election process is the same as HSRP, so it is very important to reasonably plan the priority of GLBP.

Understand GLBP Load Balancing Methods

In a GLBP group, automatic traffic load balancing is the biggest feature of GLBP, and HSRP and VRRP cannot be achieved. What load balancing solutions will GLBP provide?

Host-dependent ):This scheme will always allow a host to use the same AVF for traffic forwarding. It depends on determining the MAC address of the source host, only the source MAC address is the same, this indicates that the traffic is from the same host, and the same AVF and traffic forwarding are always used. If the traffic is from another host, another AVF will be used for traffic forwarding.

Round robin (round robin ):In turn, each AVF in GLBP is used for traffic forwarding. This is the default load balancing method of GLBP.

Weight-Based Load Balancing weighted ):The higher the weight, the more likely it is to be elected as a forwarder.

Configure different load balancing methods as follows:

R1 (config-if) # glbp 100 load-balancing?

Host-dependentLoad balance equally, source MAC determinesforwarder choice

Round-robinLoad balance equally using each forwarderin turn

WeightedLoad balance in proportion to forwarderweighting

Demonstration: Implementation of GLBP

Demonstration objectives:Implement GLBP and analyze the management data frame of AVG.

Demo environment:Figure 9.135.

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Demonstration Background:Configure GLBP on routers R1 and R2 to achieve traffic load balancing and fault redundancy.

Demo steps:

Step 1:Configure the GLBP function on routers R1 and R2 as follows:

GLBP of router R1Configuration:

R1 (config) # interfacee1/0

R1 (config-if) # glbp100 ip 192.168.2.100 * configure the virtual IP address of the GLBP group 100

R1 (config-if) # glbp100 priority 120 * configure the GLBP group 100 priority for this interface

R1 (config-if) # glbp100 preempt * configure the AVG role preemption function in GLBP

GLBP of vror2 R2Configuration:

R2 (config) # interfacee1/0

R2 (config-if) # glbp100 ip address 192.168.2.100

R2 (config-if) # glbp 100 priority 110

R2 (config-if) # glbp 100 preempt

Step 2:After completing the above configuration, you can use the command show glbpe1/0 on router R1 to view the interface as shown in Figure 9.136. It is clear that the virtual IP address of GLBP group 100 is 192.168.2.100; the load balancing method is cyclic load balancing round-robin) that uses each AVF in GLBP in turn for traffic forwarding in turn. This is the default load balancing method of GLBP, you can also clearly see the virtual MAC addresses of different AVF.

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Step 3:If the current working status of GLBP is identified, ping192.168.5.2 is performed on the host 192.168.2.4 and 192.168.2.3 respectively. If no configuration error occurs, the two hosts should successfully ping 192.168.5.2, then run the ARP-a command on the two hosts to view the current ARP resolution, as shown in Figure 9.137 and figure 9.138, the same IP address 192.168.2.100 corresponds to two virtual MAC addresses with different AVF addresses. This means that if both R1 and R2 are in good state, GLBP performs traffic load balancing.

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Then, the route forwarding of the target 192.168.5.2 is tracked on the host of 192.168.2.4 and 192.168.2.3 respectively, as shown in Figure 9.139 and 9.140. Different AVF forwarding methods are indeed adopted, and Server Load balancer is executed.

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Step 4:In this case, if the ARP response data frame of the host 192.168.2.4 and 192.168.2.3 is successfully captured by the AVG router R1, as shown in Figure 9.141, it fully proves that the ARP response host in the whole GLBP network is an AVG router. In other words, you can understand that the owner of the GLBP group is determined by the AVG.

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