Introduction
During my university studies I was doing a diploma thesis in field of Redundant and reliable networking. The purpose of itwas to create LAB examples for students, so they can test First Hop Redundancy Protocols (FHRP) , Any Transport over MPLS (AToM) and Border Gateway Protocol (BGP) on Cisco platform. These tasks are created to Virtlab (Virtual lab with physical Cisco routers) however configuration is valid and tested on physical Cisco routers as well.
Each task in the series will have its separate post with brief description of the task and schema. Complete task can be downloaded on My Skydrive
ZIP file contains:
-
*.HTML file – complete step by step guide how to perform the task
- *.PNG – pictures with topology and others
- *_preconf.txt – file with basic configuration of topology to be able to focus on task goal (IP addresses, interfaces and so on)
- *_end.txt – file with complete configuration. Once put to the routers, you will get working task
- *.dia – Topology in free DIA editor
- *.XML – topology in XML format
To complete the task:
-
Connect your environment accorrding the topology
- open the file *_preconf.txt from ZIP file with complete task and configure your environment with basic settings so you can start with the task.
GLBP – Basic – Round Robin
Title: GLBP – Basic – Round Robin
Goal:
- Configure Gateway Load Balancing Protocol on 192.168.1.0/24 network segment. One group of hosts resides on network segment.
- PC1 and PC3 represents group 1, its default gateway address is 192.168.1.1.
- Load balancing is set to round robin by default. Test load balancing functionality.
Required time: 120 minutes
Theoretical background:
Links related to this task:
Topology:
Configuration:
1) Basic IP settings
OSPF will be used for routing.
PC1
pc1:~#ifconfig eth0 192.168.1.20 netmask 255.255.255.0; set IP address for PCx
pc1:~#route add default gw 192.168.1.1; set default gateway to GLBP group 1 virtual address
PC2
pc2:~#ifconfig eth0 20.0.0.2 netmask 255.0.0.0; set IP address for PCx
pc2:~#route add default gw 20.0.0.1; set default gateway to IP address of EDGE router
PC3
pc3:~#ifconfig eth0 192.168.1.120 netmask 255.255.255.0; set IP address for PCx
pc3:~#route add default gw 192.168.1.1; set default gateway to GLBP group 1 virtual address
Router RLB1
RLB1(config)#interface #RLB1:RLB1-SW1#; configure physical interface IP address of GLBP enabled interface
RLB1(config-if)#ip address 192.168.1.251 255.255.255.0; physical IP address of GLBP enabled interface
RLB1(config-if)#no shutdown
RLB1(config)#interface #RLB1:EDGE-RLB1#; configure interface facing to the external network
RLB1(config-if)#ip address 172.16.1.1 255.255.0.0
RLB1(config-if)#no shutdown
RLB1(config-if)#exit
RLB1(config)#router ospf 1 ; configure routing protocol for internal and external network
RLB1(config-router)#network 172.16.1.0 0.0.255.255 area 0
RLB1(config-router)#network 192.168.1.0 0.0.0.255 area 0
Router RLB2
Apply analogical settings for the router RLB2.
RLB2(config)#interface #RLB2:RLB2-SW1#
RLB2(config-if)#ip address 192.168.1.252 255.255.255.0
RLB2(config-if)#no shutdown
RLB2(config)#interface #RLB2:EDGE-RLB2#; configure interface facing to the external network
RLB2(config-if)#ip address 172.17.1.1 255.255.0.0
RLB2(config-if)#no shutdown
RLB2(config-if)#exit
RLB2(config)#router ospf 1
RLB2(config-router)#network 172.17.1.0 0.0.255.255 area 0
RLB2(config-router)#network 192.168.1.0 0.0.0.255 area 0
Router EDGE
EDGE(config)#interface #EDGE:PC2-EDGE# ; this network simulates the Internet
EDGE(config-if)#ip address 20.0.0.1 255.0.0.0
EDGE(config-if)#no shutdown
EDGE(config-if)#exit
EDGE(config)#interface #EDGE:EDGE-RLB2#
EDGE(config-if)#ip address 172.17.1.2 255.255.0.0
EDGE(config-if)#no shutdown
EDGE(config-if)#exit
EDGE(config)#interface #EDGE:EDGE-RLB1#
EDGE(config-if)#ip address 172.16.1.2 255.255.0.0
EDGE(config-if)#no shutdown
EDGE(config-if)#exit
2) PC1,PC3 -> PC2 connectivity test
Use the following command to test connectivity.
pc1:~#ping 20.0.0.2; ping command is unsuccessful - no GW could be found
pc3:~#ping 20.0.0.2; ping command is unsuccessful - no GW could be found
3) GLBP settings
Router RLB1
RLB1(config)#interface #RLB1:RLB1-SW1# ; enter physical internal interface configuration mode
RLB1(config)#glbp 1 ip 192.168.1.1 ; set virtual GLBP address for group 1
RLB1(config)#glbp 1 name GROUP1 ; set name for group 1
RLB1(config)#glbp 1 priority 50 ; configure GLBP priority - higher value means higher priority, RLB1 will be active forwarder for group 1 other
RLB1(config)#glbp 1 forwarder preempt ; allow this router to overthrow lower priority forwarders
RLB1(config)#glbp 1 preempt delay minimum 2 ; set overthrow priority minimum delay for 2 seconds
Router RLB2
RLB2(config)#interface #RLB2:RLB2-SW1#
RLB2(config-if)#glbp 1 ip 192.168.1.1
RLB2(config-if)#glbp 1 name GROUP1
RLB2(config-if)#glbp 1 priority 40
RLB2(config-if)#glbp 1 forwarder preempt
RLB2(config-if)#glbp 1 preempt delay minimum 2
Function test:
1) test ping from PC1,PC3 to PC2
pc1:~#ping 20.0.0.2; ping command is successful - GW could be found as virtual address 192.168.1.1
pc3:~#ping 20.0.0.2; ping command is successful - GW could be found as virtual address 192.168.1.2
2) Display GLBP information
RLB1# sh glbp; this router is Active Virtual Forwarder
RLB1# debug glbp; debug will show GLBP communication between nodes
RLB2# sh glbp; see result, this router is conditional forwarder for group 1
3) Generate traffic to test round robin functionality
Repeat following steps several times to see changes of the route between both nodes.
pc1:~#arp -d 192.168.1.1; remove host record for default GW from ARP table
pc1:~#traceroute 20.0.0.2; trace route to outside host 20.0.0.2
pc3:~#arp -d 192.168.1.1; clean host record for default GW from ARP table
pc3:~#traceroute 20.0.0.2; remove route to outside host 20.0.0.2
4) Change priority of RLB1 (to overthrow AVF to RLB2)
RLB1(config-if)#glbp 1 priority 30
