GLBP Gateway Load Balancing Protocol

Transcription

1 GLBP Gateway Load Balancing Protocol By MEDDANE Redouane Cisco Instructor 1

2 How GLBP Works. GLBP works by making use of a single virtual IP address, which is configured as the default gateway on the hosts. The different routers that assume the forwarding role use different virtual MAC addresses for the same virtual IP address which is used to forward packets. Unlike HSRP and VRRP, GLBP does not use a single virtual MAC address for the entire group. Instead, the AVG assigns different virtual MAC addresses to each of the physical routers in the group. There are two types of routers in a GLBP group use in redundancy and load balancing: Active Virtual Gateway(AVG): Within a GLBP group,one virtual router (gateway) is elected as the Active Virtual Gateway(AVG), and its responsible for the operation of the protocol. This AVG router has the highest priority value or IP address in the group, it responds to all ARP requests for MAC addresses which it send to the virtual router IP address. Active Virtual Forwarder (AVF) A router within a GLBP group is elected as Active Virtual Forwarder (AVF) This AVF is responsible for forwarding packets sent to the mac address returned by the AVG router. Multiple active virtual forwarders can exist for each GLBP group. So, when a client needs to send packet to known default gateway (AVG) with configured IP address, it requests for the MAC address by sending an ARP (address resolution protocol) request on the subnet. The AVG will respond to these ARP requests with the virtual MAC address of each "active" virtual forwarders, based on a configured load sharing algorithm. 2

3 Practice Lab GLBP: 3

4 The topology uses The Hosts have two Routers to access the outside network, two hosts in VLAN 10 and two Hosts in VLAN 20. The GLBP protocol will be configured to allow redundancy. The requirements: VLAN 10: -The Group number is 1. -R1 is the Active router. -R2 is the standby router. VLAN 20: -The Group number is 2. -R2 is the Active router. -R1 is the standby router. -The Virtual ip Address is load-balancing is round-robin which means Each AVF in turn is included in address resolution replies for the virtual IP address. R1(config)#interface fastethernet 0/0 R1(config-if)#no shutdown R1(config)#interface fastethernet 0/0.10 R1(config-subif)#encapsulation dot1q 10 R1(config-if)#ip address R1(config-if)#glbp 1 ip R1(config-if)#glbp 1 priority 150 R1(config-if)#glbp 1 preempt R1(config-if)#glbp 1 load-balancing round-robin R2(config)#interface fastethernet 0/0 R2(config-if)#no shutdown R2(config)#interface fastethernet 0/0.10 R2(config-subif)#encapsulation dot1q 10 R2(config-if)#ip address R2(config-if)#glbp 1 ip R2(config-if)#glbp 1 preempt R2(config-if)#glbp 1 load-balancing round-robin 4

5 The Switch SW1 is configured as follow: 5

6 The first Part of the following output dislayed below concerns the AVG R1 So R1 is the AVG and it is in active state because it has a higher priority than R2 which is in the standby state. The second part concerns the AVFs. We can see that there are two AVF: -R1 is the AVF 1 and it has the Active state, R2 is in the Listen state -R2 is the AVF 2 and it has the Active state, R1 is in the Listen state 6

7 R1#show glbp FastEthernet0/ Group 1 State is Active 2 state changes, last state change 00:00:47 Virtual IP address is Hello time 3 sec, hold time 10 sec Next hello sent in secs Redirect time 600 sec, forwarder time-out sec Preemption enabled, min delay 0 sec Active is local Standby is , priority 100 (expires in sec) Priority 150 (configured) Weighting 100 (default 100), thresholds: lower 1, upper 100 Load balancing: round-robin Group members: c ( ) local c ( ) There are 2 forwarders (1 active) Forwarder 1 State is Active 1 state change, last state change 00:00:37 MAC address is 0007.b (default) Owner ID is c Redirection enabled Preemption enabled, min delay 30 sec Active is local, weighting 100 Forwarder 2 State is Listen MAC address is 0007.b (learnt) Owner ID is c Redirection enabled, sec remaining (maximum 600 sec) Time to live: sec (maximum sec) Preemption enabled, min delay 30 sec Active is (primary), weighting 100 (expires in sec) Before doing the test of GLBP operation,we will simulate a hosts with a routers,i disable the routing and i configure the default gateway and the ip addresses of each PC in the VLAN 10 as follow: PC1(config)#no ip routing PC1(config)#ip default-gateway PC1(config)#interface fastethernet 0/0 PC1(config-if)#no shutdown PC1(config-if)#ip address PC2(config)#no ip routing PC2(config)#ip default-gateway PC2(config)#interface fastethernet 0/0 PC2(config-if)#no shutdown PC2(config-if)#ip address

8 Test of the connectivity: ping Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to , timeout is 2 seconds:!!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 24/43/64 ms PC2#ping Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to , timeout is 2 seconds:!!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 28/37/68 ms PC2# Let's verify which AVF is used to forward the ICMP Packets by looking the ARP table: 0007.b is the MAC Address of the AVF 1 (R1) b is the MAC Address if the AVF 2 (R2). show arp include Internet b ARPA FastEthernet0/0 8

9 PC2#show arp include Internet b ARPA FastEthernet0/0 PC2# Let's confirms the result by issuing a telnet from PC1 and PC2 toward the Virtual IP address : We can see that: -R1 responds to the Telnet request of the PC1 -R2 responds to the telnet request of the PC2 telnet Trying Open R1> PC2#telnet Trying Open R2> Before configuring the down test,we need to configure the GLBP for th VLAN 20, R2 is in the Active state (AVG) with the priority 150 while R1 is in Listen state with the default priority 100 as follow: R1(config)#interface fastethernet 0/0.20 R1(config-subif)#encapsulation dot1q 20 R1(config-subif)#ip address R1(config-subif)#glbp 2 ip R1(config-subif)#glbp 2 preempt R2(config)#interface fastethernet 0/0.20 R2(config-subif)#encapsulation dot1q 20 R2(config-subif)#ip address R2(config-subif)#glbp 2 ip R2(config-subif)#glbp 2 priority 150 R2(config-subif)#glbp 2 preempt 9

10 The first Part of the following output dislayed below concerns the AVG R2 So R2 is the AVG and it is in active state because it has a higher priority than R1 which is in the standby state. The second part concerns the AVFs. We can see that there are two AVF: -R1 is the AVF 1 and it has the Active state, R2 is in the Listen state -R2 is the AVF 2 and it has the Active state, R1 is in the Listen state 10

11 R2#show glbp begin FastEthernet0/0.20 FastEthernet0/ Group 2 State is Active 1 state change, last state change 00:04:41 Virtual IP address is Hello time 3 sec, hold time 10 sec Next hello sent in secs Redirect time 600 sec, forwarder time-out sec Preemption enabled, min delay 0 sec Active is local Standby is , priority 100 (expires in sec) Priority 150 (configured) Weighting 100 (default 100), thresholds: lower 1, upper 100 Load balancing: round-robin Group members: c ( ) c ( ) local There are 2 forwarders (1 active) Forwarder 1 State is Listen MAC address is 0007.b (learnt) Owner ID is c Redirection enabled, sec remaining (maximum 600 sec) Time to live: sec (maximum sec) Preemption enabled, min delay 30 sec Active is (primary), weighting 100 (expires in sec) Forwarder 2 State is Active 1 state change, last state change 00:04:29 MAC address is 0007.b (default) Owner ID is c Redirection enabled Preemption enabled, min delay 30 sec Active is local, weighting 100 Let's configure PC3 and PC4: PC3(config)#no ip routing PC3(config)#ip default-gateway PC3(config)#interface fastethernet 0/0 PC3(config-if)#no shutdown PC3(config-if)#ip address PC4(config)#no ip routing PC4(config)#ip default-gateway PC4(config)#interface fastethernet 0/0 PC4(config-if)#no shutdown PC4(config-if)#ip address

12 Let's test the connectivity between the PC1 in the VLAN 10 and the PC3 in the VLAN 20: ping Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to , timeout is 2 seconds:!!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 56/69/92 ms Remember that PC1 uses R1 to forward the traffic therefore it uses the MAC Address of R1 (0007.b ): We can confirm the result by launching a traceroute toward the PC3 from PC1 as follow: Notice that the packets go through R1 ( ): traceroute Type escape sequence to abort. Tracing the route to msec 24 msec 32 msec msec * 48 msec 12

13 Now we launch a ping from PC1 toward PC3 while disabling the interface fa0/0 of R1: R1(config)#int fa0/0 R1(config-if)#shu R1(config-if)#shutdown ping repeat 140 Type escape sequence to abort. Sending 140, 100-byte ICMP Echos to , timeout is 2 seconds:!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!...!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Success rate is 96 percent (135/140), round-trip min/avg/max = 36/53/92 ms Let's verify which Gateway is used by PC1: Now it uses R2 instead of R1 used previously: telnet Trying Open R2> PC1 uses the MAC Address of R2 (0007.b ) but it's R1 which responds to the ARP request of PC1 because it is an AVG: show arp include Internet b ARPA FastEthernet0/0 13

14 The traceroute confirms that the pacet now go through R2( ): traceroute Type escape sequence to abort. Tracing the route to msec 32 msec 28 msec msec * 64 msec Finally PC1 does not see the changes. To reduce the timers in order to have a fastest... R1(config)#interface FastEthernet0/0.10 R1(config-subif)#glbp 1 timers msec 150 msec 500 R1(config-subif)#interface FastEthernet0/0.20 R1(config-subif)#glbp 2 timers msec 150 msec 500 R2(config)#interface FastEthernet0/0.10 R2(config-subif)#glbp 1 timers msec 150 msec 500 R2(config-subif)#interface FastEthernet0/0.20 R2(config-subif)#glbp 2 timers msec 150 msec 500 The timers should be changed on the rwo routers and the two group (1 and 2) 14

15 Now we launch the ping from PC1 toward PC3 while activating the interface fa0/0 of R1: R1(config-subif)#int fa0/0 R1(config-if)#no shu R1(config-if)#no shutdown ping repeat 140 Type escape sequence to abort. Sending 140, 100-byte ICMP Echos to , timeout is 2 seconds:!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Success rate is 99 percent (139/140), round-trip min/avg/max = 40/56/92 ms 15