Tag Archives: 3.5f

3.5.f Implement and troubleshoot load-balancing

3.5.f [i] equal-cost

Load balancing is the capability of a router to distribute traffic over all the router network ports that are the same distance from the destination address. Load balancing increases the utilization of network segments, and so increases effective network bandwidth. Equal cost path load balancing is applicable when different paths to a destination network report the same routing metric value. The maximum-paths command determines the maximum number of routes that the routing protocol can use.

Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 3210-3213).  . Kindle Edition.

http://routeswitchlabtips.com/routing/setting-a-preferred-route-with-equal-cost-routes-in-eigrp/

3.5.f Implement and troubleshoot load-balancing

3.5.f [ii] unequal-cost

Unequal cost path load balancing is applicable when different paths to a destination network are of different routing metric values. The variance command determines which of these routes is used by the router.

Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 3215-3217).  . Kindle Edition.

http://www.informit.com/library/content.aspx?b=CCIE_Practical_Studies_I&seqNum=126

3.5.f Implement and troubleshoot load-balancing

3.5.f [iii] add-path

The Add Path feature in EIGRP feature enables hubs in a single Dynamic Multipoint VPN (DMVPN) domain to advertise multiple best paths to connected spokes when the Enhanced Interior Gateway Routing Protocol (EIGRP) is the routing protocol between the hubs and the spokes.

add-paths number command enables EIGRP to advertise multiple paths as best paths to connected spokes in a single Dynamic Multipoint VPN (DMVPN) domain.

Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 3219-3223).  . Kindle Edition.

http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_eigrp/configuration/xe-3s/ire-xe-3s-book/ire-add-path.html

 

3.5.f unequal-cost (EIGRP)

note: the bandwidth of the interfaces have been artificially adjusted for illustration

eigrp_unequal_costs

r1#sh ip proto
Routing Protocol is “eigrp 123”
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 123
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      00:34:41
192.168.2.2           90      00:01:20
192.168.3.2           90      00:01:20
192.168.1.2           90      00:01:20
Distance: internal 90 external 170

r1#sh ip eigrp topo
IP-EIGRP Topology Table for AS(123)/ID(1.1.1.1)

Codes: P – Passive, A – Active, U – Update, Q – Query, R – Reply,
r – reply Status, s – sia Status

P 1.1.1.0/24, 1 successors, FD is 128256
via Connected, Loopback0
P 3.3.3.0/24, 1 successors, FD is 3142400
via 192.168.1.2 (3142400/156160), Serial0/0
via 192.168.2.2 (5642496/156160), Serial0/1
via 192.168.3.2 (20642560/156160), Serial0/2

the feasible distance is established at 3142400, hence s0/0 is the successor route.  for s0/1 the feasible distance is nearly twice that of s0/0.

since the default variance is 1, the ip routing table will only display the successor.

if the variance is doubled (2 X 3142400) the ip routing table will now recognize near equal cost routes:

r1(config-router)#do sh run | b router
router eigrp 123
variance 2
network 0.0.0.0
no auto-summary

r1(config-router)#do sh ip route | b Gate
Gateway of last resort is not set

1.0.0.0/24 is subnetted, 1 subnets
C       1.1.1.0 is directly connected, Loopback0
3.0.0.0/24 is subnetted, 1 subnets
D       3.3.3.0 [90/5642496] via 192.168.2.2, 00:01:06, Serial0/1
                [90/3142400] via 192.168.1.2, 00:01:06, Serial0/0

3.5.f equal-cost (EIGRP)

eigrp_equal_cost

equal cost over two paths from r1 to network 192.168.23.0/24…

r1#sh ip route 192.168.23.0
Routing entry for 192.168.23.0/24
Known via “eigrp 1”, distance 90, metric 30720, type internal
Redistributing via eigrp 1
Last update from 192.168.12.2 on FastEthernet0/0, 00:05:49 ago
Routing Descriptor Blocks:
* 192.168.13.3, from 192.168.13.3, 00:05:49 ago, via FastEthernet1/0
Route metric is 30720, traffic share count is 1
Total delay is 200 microseconds, minimum bandwidth is 100000 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 1
192.168.12.2, from 192.168.12.2, 00:05:49 ago, via FastEthernet0/0
Route metric is 30720, traffic share count is 1
Total delay is 200 microseconds, minimum bandwidth is 100000 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 1/255, Hops 1

this can also be viewed from the topology table…

r1#sh ip eigrp topo 192.168.23.0
IP-EIGRP (AS 1): Topology entry for 192.168.23.0/24
State is Passive, Query origin flag is 1, 2 Successor(s), FD is 30720
Routing Descriptor Blocks:
192.168.12.2 (FastEthernet0/0), from 192.168.12.2, Send flag is 0x0
Composite metric is (30720/28160), Route is Internal
Vector metric:
Minimum bandwidth is 100000 Kbit
Total delay is 200 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 1
192.168.13.3 (FastEthernet1/0), from 192.168.13.3, Send flag is 0x0
Composite metric is (30720/28160), Route is Internal
Vector metric:
Minimum bandwidth is 100000 Kbit
Total delay is 200 microseconds
Reliability is 255/255
Load is 1/255
Minimum MTU is 1500
Hop count is 1

eigrp defaults load sharing across equal cost paths…

r1#sh ip route | b Gate
Gateway of last resort is not set

C    192.168.12.0/24 is directly connected, FastEthernet0/0
1.0.0.0/24 is subnetted, 1 subnets
C       1.1.1.0 is directly connected, Loopback0
C    192.168.13.0/24 is directly connected, FastEthernet1/0
2.0.0.0/24 is subnetted, 1 subnets
D       2.2.2.0 [90/156160] via 192.168.12.2, 00:10:07, FastEthernet0/0
3.0.0.0/24 is subnetted, 1 subnets
D       3.3.3.0 [90/156160] via 192.168.13.3, 00:10:07, FastEthernet1/0
D    192.168.23.0/24 [90/30720] via 192.168.13.3, 00:10:09, FastEthernet1/0
                     [90/30720] via 192.168.12.2, 00:10:09, FastEthernet0/0