To be successful CCNA exam, you should know better what Split Horizon is the way to turn it off and when to turn it off. Knowing when the horizon is in turn cleaved important in production networks, because it spoke network is to have incomplete routing tables on the one-to-hub and spokes.
Split Horizon is available for one simple reason - routing loop prevention. The rule of split horizon states that a router does not send an advertisement for a way out of the same interface arose. Split Horizon is standard on all interfaces running RIP, IGRP, EIGRP, e.
serve this CCNA tutorial, R1 and R2 and R3 as a hub, the spokes will be. We first configure EIGRP on the network 172.16.123.0 / 24, the network between the three routers.
R1 # conf t
R1 (config) # router EIGRP 100
R1 (config-router) # no auto-summary
R1 (config-router) # network 172.12.123.0 0.0.0.255
R2 # conf t
R2 (config) #> Router EIGRP 100
R2 (config-router) # no auto-summary
R2 (config-router) # network 172.12.123.0 0.0.0.255
R3 # conf t
R3 (config) # router EIGRP 100
R3 (config-router) # no auto-summary
R3 (config-router) # network 172.12.123.0 0.0.0.255
Running EIGRP neighbor show ip R1 shows that the districts of R2 and R3 on.
R1 # show ip EIGRP neighbor
IP-EIGRP neighbors process 100
H AddressInterface Hold Uptime SRTT RTO Q Seq Type
(Sec) (ms) Cnt Num
SE0 172.12.123.3 1 / 0 11 00:02:45 1 5000 0 1
SE0 172.12.123.2 0 / 0 161 00:03:01 1 5000 0 1
Each router now advertise its loopback address via EIGRP.
R1 # conf t
R1 (config) # router EIGRP 100
R1 (config-router) # network 1.1.1.00.0.0.255
R2 # conf t
R2 (config) # router EIGRP 100
R2 (config-router) # network 2.2.2.0 0.0.0.255
R3 # conf t
R3 (config) # router EIGRP 100
R3 (config-router) # network 3.3.3.0 0.0.0.255
Running EIGRP show ip route each router shows that R1 has a loopback path for both R2 and R3. R1 R2 and R3 only see the loopback address and not against each other. Why?
R1 # show ip route EIGRP
2.0.0.0/24 is subnetted, 1Subnets
D 2.2.2.0 [90/2297856] via 172.12.123.2, 00:03:19, Serial0 / 0
3.0.0.0/24 is subnetted, 1 subnets
D 3.3.3.0 [90/2297856] via 172.12.123.3, 00:03:04, Serial0 / 0
R2 # show ip route EIGRP
1.0.0.0/24 is subnetted, 1 subnets
D 1.1.1.0 [90/2297856] via 172.12.123.1, 00:03:40, Serial0/0.123
R3 # show ip route EIGRP
1.0.0.0/24 is subnetted, 1 subnets
D 1.1.1.0 [90/2297856] via 172.12.123.1, 00:05:17, Serial0/0.31
EIGRPSplit Horizon default to prevent routing loops. In this laboratory, however, prevents full network access. R2 and R3 both form neighbor relationship with R1 physical serial interface. R2 advertises its loopback address to R1 serial port, as well as R3. Split Horizon is not a return path to receive for the same interface that was advertised to be. This prevents the R1 R2 R3 from advertising to loopback, loopback R3 or R2.
Split Horizon must be disabled to allownetwork to reach full capacity in this workshop. These are not IP split-horizon eigrp 100 on R1 the serial interface. When split horizon is disabled, will result in the nearby
Relationships fail, and then restore. Run route show ip eigrp 100 on both R2 and R3. The appropriate path for the remote loopback address will now appear.
R1 # conf t
R1 (config) # int Serial0
R1 (config-if) # no ip split-horizon eigrp 100
10:02:23:% DUAL-5-NBRCHANGE: IP-EIGRP 100: NeighborAmended Split Horizon: 172.12.123.2 (Serial0 / 0) down
10:02:23:% DUAL-5-NBRCHANGE: IP-EIGRP 100: Neighbor 172.12.123.3 (Serial0 / 0) down: split horizon changed
10:02:27:% DUAL-5-NBRCHANGE: IP-EIGRP 100: Neighbor 172.12.123.3 (Serial0 / 0) ip: new district
10:02:54:% DUAL-5-NBRCHANGE: IP-EIGRP 100: Neighbor 172.12.123.2 (Serial0 / 0) ip: new district
R2 # show ip route EIGRP
1.0.0.0/24 is subnetted, 1 subnets
D 1.1.1.0 [90/2297856] via 172.12.123.1, 00:00:06,Serial0/0.123
3.0.0.0/24 is subnetted, 1 subnets
D 3.3.3.0 [90/2809856] via 172.12.123.1, 00:00:06, Serial0/0.123
R3 # show ip route EIGRP
1.0.0.0/24 is subnetted, 1 subnets
D 1.1.1.0 [90/2297856] via 172.12.123.1, 00:00:12, Serial0/0.31
2.0.0.0/24 is subnetted, 1 subnets
D 2.2.2.0 [90/2809856] via 172.12.123.1, 00:00:12, Serial0/0.31
Disabling split horizon should be done with caution, but know when and where to do, shows thatYou really understand how this technology works - and what a big step on the way to earn your CCNA's!
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