Demonstration: Non-equivalent Server Load balancer (Fault Analysis and Solution)

Demonstration

Fault Background:In the network environment as shown in Figure 14.20, engineers have completed the startup of the dynamic routing protocol for all router interface addresses in the environment. Currently, the neighbor relationship of each VPN Router is normal, and route learning is normal, to make full use of the non-equivalent Server Load balancer feature, engineers need to generate two routes with non-equivalent overhead to the target subnet 172.17.1.0/24 in the router R1 routing table, when the Engineer wants to adjust the variance on router R1, he finds that there is only one optimal route to the target 172.17.1.0/24 through the next hop R2192.168.1.2 In the router table, as shown in Figure 14.21 below, then, when you run Show ip VPN 2013 topology on router R1 to view the overhead of the standby path in the VPN topology table, as shown in Figure 14.22 in the following figure, it is found that the standby path is not placed in the topology table of the VPN gateway, according to the principle of network replication: in this case, you will not be able to perform the variance value calculation according to the normal steps. The reason is very simple. In the routing table of R1, the Standby path is It usually appears in the routing table only after the variance value is calculated and configured. However, the premise of this process is that if the standby path is not placed in the OSPF topology table, there is no chance for engineers to calculate the variance value. Now we need to solve this problem. First, we need to analyze why the standby path R1 reaches 172.16.1.0/24 through R2. It is not put into the VPN topology of R2, finally, it implements the non-equivalent Server Load balancer.

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Original configuration for fault generation:The original configuration of the fault generation is as follows, which makes it easier for readers to see the current fault situation when restructuring the fault, so as to analyze the fault more scientifically.

Original configuration of router R1:

InterfaceEthernet1/0

Ip address 192.168.1.1 255.255.255.0

Duplex half

!

InterfaceEthernet1/1

Ip address 192.168.2.1 255.255.255.0

Duplex half

!

Router VPN 2013

Network 192.168.1.0

Network 192.168.2.0

Original configuration of vror2 R2:

InterfaceEthernet1/0

Ip address 192.168.1.2 255.255.255.0

Duplex half

!

InterfaceEthernet1/1

Ip address 192.168.3.1 255.255.255.0

Duplex half

!

Router VPN 2013

Network 172.16.0.0

Network 192.168.1.0

Network 192.168.3.0

Router R3Original Configuration:

InterfaceEthernet1/0

Ip address 192.168.3.2 255.255.255.0

Duplex half

!

InterfaceEthernet1/1

Ip address 192.168.2.2 255.255.255.0

Duplex half

!

Router VPN 2013

Network 192.168.2.0

Network 192.168.3.0

Fault analysis:According to the principle of storing the standby path in the topology table: the advertised distance from the neighbor router to the AD must be less than the feasible distance FD, otherwise there may be a routing loop. In the fault environment shown in Figure 14.20, the overhead of router R1 from router R2 to router 172.16.1.0/24 is the FD of router R1; the overhead of router R1 neighbor R3 to 172.16.1.0/24 is the advertised distance of router R1's AD neighbor ); you can run the show ipvpn 2013 topology command on the routers R1 and R3 to view FD and AD, as shown in Figure 14.23.It can be seen that the AD is equal to FD at this time, so the standby path will not be placed in the OSPF topology table of router R1.

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Solution:The above analysis shows the cause of the fault. Now we need to solve this fault. We need to make router R3 the backup path from router R1 to router 172.16.1.0/24, in this case, the Active AD is equal to FD in the current environment, and the active AD must be smaller than FD. To achieve this goal, you can adjust the delay of the E1/0 interface of router R3. Of course, the bandwidth, latency, load, reliability, MTU of multiple composite parameters are used for the calculation of the OSPF route metric value ),However, we recommend that you adjust the latency to a lower latency than the expected Active Directory, so that the FD is smaller than the Active Directory, the standby path R3 will be placed in the router R1 topology table. The following figure shows the configuration for adjusting the router R3 latency. The default latency of the 10 MB Ethernet interface is 1000 microseconds, now use the command delay 50 to change it to 500 microseconds. Because 10 microseconds is a unit, you can configure 50 here.The changes before and after latency adjustment are shown in Figure 14.24. After changing the delay configuration, view FD on router R1 again, and view AD on router R3, as shown in Figure 14.25. At this time, AD is smaller than FD, two routes to the target subnet 172.16.1.0/24 are displayed in the router R1 topology table.

To change the delay configuration of the network replication gateway, run the following command:

R3 (config) # interface e1/0

R3 (config-if) # delay 50

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Now that the non-equivalent load balancing conditions are met, use AD409600 divided by fd0000800 to integer and Add 1 to get 2, and then implement the following configuration. After the configuration is complete, you can view the route table on router R1, as shown in Figure 14.26 below. Two non-equivalent routes have been displayed.

Configure the variance value for non-equivalent load balancing:

R1 (config) # router VPN 2013

R1 (config-router) # variance 2

R1 (config-router) # exit

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