EIGRP Load Balancing


EIGRP Load Balancing

 

Let’s concentrate on network 200.0.0.1 , we have four options available to us

  • R7(config)#do sh ip route eig
  •      100.0.0.0/24 is subnetted, 3 subnets
  • D       100.100.100.0
  •            [90/2177536] via 150.100.221.6, 00:03:30, FastEthernet0/1
  •            [90/2177536] via 150.100.221.5, 00:03:30, FastEthernet0/1
  •            [90/2177536] via 150.100.220.6, 00:03:30, FastEthernet0/0
  •            [90/2177536] via 150.100.220.5, 00:03:30, FastEthernet0/0
  • D       100.100.200.0 [90/2172416] via 150.100.78.8, 00:03:07, Serial0/0
  • D       100.100.250.0
  •            [90/2174976] via 150.100.221.6, 00:03:30, FastEthernet0/1
  •            [90/2174976] via 150.100.220.6, 00:03:30, FastEthernet0/0
  •      200.0.0.0/32 is subnetted, 8 subnets
  • D       200.0.0.8 [90/2297856] via 150.100.78.8, 00:03:07, Serial0/0
  • D       200.0.0.9 [90/2300416] via 150.100.221.6, 00:03:30, FastEthernet0/1
  •                   [90/2300416] via 150.100.220.6, 00:03:30, FastEthernet0/0
  • D       200.0.0.1 [90/2302976] via 150.100.221.6, 00:03:30, FastEthernet0/1
  •                   [90/2302976] via 150.100.221.5, 00:03:30, FastEthernet0/1
  •                   [90/2302976] via 150.100.220.6, 00:03:31, FastEthernet0/0
  •                   [90/2302976] via 150.100.220.5, 00:03:31, FastEthernet0/0
  • D       200.0.0.2 [90/2300416] via 150.100.221.6, 00:03:31, FastEthernet0/1
  •                   [90/2300416] via 150.100.221.5, 00:03:31, FastEthernet0/1
  •                   [90/2300416] via 150.100.220.6, 00:03:31, FastEthernet0/0
  •                   [90/2300416] via 150.100.220.5, 00:03:31, FastEthernet0/0
  • D       200.0.0.4 [90/2812416] via 150.100.221.6, 00:03:31, FastEthernet0/1
  • The cost on all of those happens to be the same so by default what is have in eigrp is equal cost load balancing , take a look at s hip protocols output and we have maximum paths of 4 :
  • R7(config)#do sh ip prot
  • Routing Protocol is “eigrp 666”
  •   Outgoing update filter list for all interfaces is not set
  •   Incoming update filter list for all interfaces is not set
  •   Default networks flagged in outgoing updates
  •   Default networks accepted from incoming updates
  •   EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0
  •   EIGRP maximum hopcount 100
  •   EIGRP maximum metric variance 1
  •   Redistributing: eigrp 666
  •   EIGRP NSF-aware route hold timer is 240s
  •   Automatic network summarization is not in effect
  •   Maximum path: 4
  •   Routing for Networks:
  •     0.0.0.0
  •   Routing Information Sources:
  •     Gateway         Distance      Last Update
  •     (this router)         90      00:06:19
  •     150.100.220.6         90      00:05:55
  •     150.100.221.6         90      00:05:55
  •     150.100.221.5         90      00:05:54
  •     150.100.220.5         90      00:05:54
  •     150.100.78.8          90      00:05:55
  •   Distance: internal 90 external 170
  • So what options do we have to manipulate that , we can say
  • R7(config)#router eigrp 666
  • R7(config-router)#maxi
  • R7(config-router)#maximum-paths ?
  •   <1-16>  Number of paths
  • Nowadays we have 16 paths ….. so things being equal that’s what we’re gonna do basic load balancing
  • R5#sh ip eigr top | b 200.0.0.1
  • IP-EIGRP Topology Table for AS(666)/ID(200.0.0.5)
  • Codes: P – Passive, A – Active, U – Update, Q – Query, R – Reply,
  •        r – reply Status, s – sia Status
  • P 200.0.0.1/32, 2 successors, FD is 2300416
  •         via 150.100.25.2 (2300416/156160), Serial1/2
  •         via 150.100.100.2 (2300416/156160), Serial0/1
  • we have to path to get to network 200.0.0.1 so  let’s do soma damage
  • R5(config)#int s 0/1
  • R5(config-if)#band
  • R5(config-if)#bandwidth 768
  • R5(config-if)#do sh int s 0/1
  • Serial0/1 is up, line protocol is up
  •   Hardware is GT96K Serial
  •   Internet address is 150.100.100.5/24
  •   MTU 1500 bytes, BW 768 Kbit, DLY 20000 usec,
  •      reliability 255/255, txload 1/255, rxload 1/255
  •   Encapsulation FRAME-RELAY, loopback not set
  • Now we see that we have one path in a routing table and 2 paths in topology table the other being a back up paths
  • R5(config-if)#do sh ip route eigr | be 200.0.0.1
  • D       200.0.0.1 [90/2300416] via 150.100.25.2, 00:00:38, Serial1/2
  • D       200.0.0.2 [90/2297856] via 150.100.25.2, 00:00:38, Serial1/2
  • D       200.0.0.4 [90/2809856] via 150.100.25.2, 00:00:38, Serial1/2
  • D       200.0.0.6 [90/156160] via 150.100.221.6, 00:16:09, FastEthernet0/1
  • R5(config-if)#do sh ip eigrp top | be 200.0.0.1
  • P 200.0.0.1/32, 1 successors, FD is 2300416
  •         via 150.100.25.2 (2300416/156160), Serial1/2
  •         via 150.100.100.2 (3975680/156160), Serial0/1
  • P 200.0.0.2/32, 1 successors, FD is 2297856
  •         via 150.100.25.2 (2297856/128256), Serial1/2
  • now we’ve changed a bandwidth and somewhere along the way during lab we get a question “hey I want you to change load balancing on there” , so the question is how are we going to do this ?
  • well we have variety of things we can use , one of the simplest one is the variance command. So variance is a multiplier for the lowest metric
  •  
  • R5(config)#router eigrp 666
  • R5(config-router)#vari
  • R5(config-router)#variance 2
  • R5(config-router)#do sh ip route eigrp | be 200.0.0.1
  • D       200.0.0.1 [90/3975680] via 150.100.100.2, 00:00:01, Serial0/1
  •                   [90/2300416] via 150.100.25.2, 00:00:01, Serial1/2
  • D       200.0.0.2 [90/3973120] via 150.100.100.2, 00:00:01, Serial0/1
  • R5(config-router)#no variance 2
  • R5(config-router)#do sh ip route eigrp | be 200.0.0.1
  • D       200.0.0.1 [90/2300416] via 150.100.25.2, 00:00:06, Serial1/2
  • D       200.0.0.2 [90/2297856] via 150.100.25.2, 00:00:06, Serial1/2
  • Now after we’ve configured variance of 2 and we do trace we get  :
  • R5(config-router)#do trace 200.0.0.1
  • Type escape sequence to abort.
  • Tracing the route to 200.0.0.1
  •   1 150.100.100.2 12 msec
  •     150.100.25.2 32 msec
  •     150.100.100.2 36 msec
  •   2 150.100.12.1 36 msec *  32 msec
  • We can see it’s load balancing so :
  • R5(config-router)#no variance 2
  • R5(config-router)#do trace 200.0.0.1
  • Type escape sequence to abort.
  • Tracing the route to 200.0.0.1
  •   1 150.100.25.2 28 msec 16 msec 20 msec
  •   2 150.100.12.1 28 msec *  32 msec
  • And we see only one single the best path is now chosen
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About ccie4all
Hello, and welcome to the first post of my CCIE blog This blog has got one simple goal and that is to improve our skills in Cisco Networking field so we can become best engineers on a job market. Wordpress Blog https://ccie4all.wordpress.com/ information about the changes made to Gns3 BGP , MPLS and R&S CCIE labs. In order to access and download all provided materials and receive important updates from Gns3 BGP , MPLS and R&S CCIE labs under GNS3 tab in the main header please go ahead and subscribe to https://ccie4all.wordpress.com/ ! All other posts have not been affected and can be accessed at any given time. Enjoy ! Tom

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