Call Toll-Free 1.888.765.8301
And Speak With A Live Telecom Consultant!
Real-Time Telecom Price Quote Tool:
Service Type:
Your Name:
Company:
Email:
Installation Phone Number: ()-


For HughesNet Satellite Internet Services
Call Toll Free: 1-877-247-5156


Cisco CCNA Exam Tutorial: Split Horizon And Hub-And-Spoke Networks

For CCNA exam success, you had better know what cut up horizon is, tips on how to turn it off, and when to show it off.  Understanding when to turn split horizon off is also necessary in production networks, because it may cause a hub-and-spoke community to have incomplete routing tables on the spokes.

Split horizon exists for a very good purpose – routing loop prevention.  The rule of split horizon states that a router can not ship an commercial for a route out the same interface that it got here in on.  Cut up horizon is on by default on all interfaces working RIP, IGRP, and EIGRP.

In this CCNA tutorial, R1 will serve, because the hub and R2 and R3 would be the spokes.  We’ll first configure EIGRP over the 172.16.123.0 /24 community, the network connecting the three routers.

R1conf t

R1(config)router eigrp a hundred

R1(config-router)no auto-abstract

R1(config-router)network 172.12.123.0 0.0.0.255

R2conf t

R2(config)router eigrp one hundred

R2(config-router)no auto-summary

R2(config-router)community 172.12.123.0 0.0.0.255

R3conf t

R3(config)router eigrp one hundred

R3(config-router)no auto-summary

R3(config-router)community 172.12.123.zero 0.0.0.255

Operating show ip eigrp neighbor on R1 shows that adjacencies to R2 and R3 are up.

R1show ip eigrp neighbor

IP-EIGRP neighbors for course of 100

H   Handle                 Interface   Maintain          Uptime   SRTT       RTO  Q  Seq Kind

                                                (sec)         (ms)       Cnt        Num

1   172.12.123.3            Se0/zero         eleven        00:02:forty five    1         5000  zero        1

0   172.12.123.2            Se0/0        161        00:03:01    1          5000  0        1
 
Every router will now promote its loopback address by way of EIGRP.

R1conf t

R1(config)router eigrp 100

R1(config-router)network 1.1.1.0 0.0.0.255

R2conf t

R2(config)router eigrp 100

R2(config-router)community 2.2.2.0 0.0.0.255
Trust in God – Practical Methods To Develop Trust in God
R3conf t

R3(config)router eigrp one hundred

R3(config-router)community 3.3.3.zero 0.0.0.255

Running present ip eigrp route on each router shows that  R1 has a route for each R2’s and R3’s loopback.  R2 and R3 will solely see R1’s loopback address, and never one another’s.  Why?

R1show ip route eigrp

     2.0.0.zero/24 is subnetted, 1 subnets

D       2.2.2.0 [90/2297856] via 172.12.123.2, 00:03:19, Serial0/0

     3.0.0.zero/24 is subnetted, 1 subnets

D       3.3.3.zero [90/2297856] via 172.12.123.3, 00:03:04, Serial0/0

R2show ip route eigrp

     1.0.0.0/24 is subnetted, 1 subnets

D       1.1.1.0 [90/2297856] by way of 172.12.123.1, 00:03:forty, Serial0/0.123

R3show ip route eigrp

     1.0.0.0/24 is subnetted, 1 subnets

D       1.1.1.0 [90/2297856] through 172.12.123.1, 00:05:17, Serial0/0.31

EIGRP uses Break up Horizon by default to stop routing loops. On this lab, though, it prevents full network reachability.  R2 and R3 each kind neighbor relationships with R1’s Serial bodily interface.  R2 advertises its loopback deal with to R1’s Serial interface, as does R3.  Cut up Horizon doesn’t enable a path to be marketed back out the identical interface it was acquired on.  This prevents R1 from advertising R2’s loopback to R3, or R3’s loopback to R2.

Cut up Horizon have to be disabled to allow full network reachability on this lab.  To take action, run no ip cut up-horizon eigrp a hundred on R1’s Serial interface.  When Split Horizon is disabled, that can cause the neighbor
relationships to fail, and then reestablish.  Run show ip route eigrp a hundred on each R2 and R3. The appropriate route to the remote loopback deal with will now appear.

R1conf t

R1(config)int serial0

R1(config-if)no ip break up-horizon eigrp a hundred

10:02:23: %DUAL-5-NBRCHANGE: IP-EIGRP one hundred: Neighbor 172.12.123.2 (Serial0/zero) down: break up horizon modified

10:02:23: %DUAL-5-NBRCHANGE: IP-EIGRP a hundred: Neighbor 172.12.123.3 (Serial0/zero) down: break up horizon modified

10:02:27: %DUAL-5-NBRCHANGE: IP-EIGRP one hundred: Neighbor 172.12.123.3 (Serial0/0) ip: new adjacency

10:02:54: %DUAL-5-NBRCHANGE: IP-EIGRP a hundred: Neighbor 172.12.123.2 (Serial0/0) ip: new adjacency

R2show ip route eigrp

     1.0.0.zero/24 is subnetted, 1 subnets

D       1.1.1.zero [90/2297856] by way of 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

R3show 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.zero [90/2809856] via 172.12.123.1, 00:00:12, Serial0/0.31

Disabling split horizon needs to be accomplished with care, however knowing when and where to do so reveals that you just actually perceive how this technology works – and that is a big step on the way in which to incomes your CCNA!

Me and you can to  free translate  this page with free translation software