howtonetwork.net

Cisco Certification Training

  • Products
  • CCNA
    • CCNA Videos
    • CCNA Lectures
    • CCNA Practice Exams
    • Challenge Labs
      • Challenge Video Solutions
    • Cisco Commands
  • CCNP ROUTE
    • ROUTE Exams
  • CCNP SWITCH
    • SWITCH Exams
  • CCNP TSHOOT
  • Home
  • Join
  • Downloads
  • About Us
  • Whitepapers
  • Feature Articles
  • Helpdesk
  • FAQ
  • Free Training
You are here: Home / IP Split-Horizon EIGRP

IP Split-Horizon EIGRP

Command

IP Split-Horizon EIGRP

Use

Split Horizon protects against routing loops by not accepting routes on the same interface that a router sends updates out.
This normally has to be turned off in hub and spoke topologies to ensure full reachability.

Syntax

Router(config-router)#network <ip address>
OR
Router(config-router)#network <ip address> <wildcard>

Example

simple

In this example we will configure EIGRP 100 on all routers in the in topology.

R1(config)#router eigrp 100
R1(config-router)#no auto
R1(config-router)#network 10.4.4.0 0.0.0.255
R1(config-router)#network 1.0.0.0

Notice that EIGRP also stripes the network statements back to its classful network boundary.

3(config)#router eigrp 100
R3(config-router)#no auto
R3(config-router)#network 3.0.0.0
R3(config-router)#network 10.4.4.0 0.0.0.255

If we configure the network statement with a wildcard, we can control what interfaces are put into EIGRP.

R4(config)#router eigrp 100
R4(config-router)#no auto
R4(config-router)#network 4.0.0.0
R4(config-router)#network 10.4.4.0 0.0.0.255

Checking the EIGRP routing tables we see that R1 and R3 have not received any routes.

R1(config-router)#do show ip route eigrp
4.0.0.0/32 is subnetted, 1 subnets
D 4.4.4.4 [90/2297856] via 10.4.4.4, 00:02:34, Serial1/0
R1(config-router)#

R3(config)#do show ip route eigrp
4.0.0.0/32 is subnetted, 1 subnets
D 4.4.4.4 [90/2297856] via 10.4.4.4, 00:02:54, Serial1/0
R3(config)#

R4(config-router)#do show ip route eigrp
1.0.0.0/32 is subnetted, 3 subnets
D 1.1.1.1 [90/2297856] via 10.4.4.1, 00:00:20, Serial0/0
D 1.3.3.3 [90/2297856] via 10.4.4.1, 00:00:20, Serial0/0
D 1.2.2.2 [90/2297856] via 10.4.4.1, 00:00:20, Serial0/0
3.0.0.0/32 is subnetted, 1 subnets
D 3.3.3.3 [90/2297856] via 10.4.4.3, 00:00:28, Serial0/0
R4(config-router)#

Now we will disable split-horizon on R4’s frame-relay interface.

R4(config-router)#int s0/0
R4(config-if)#no ip split-horizon eigrp 100
R4(config-if)#
*Mar 1 00:14:05.915: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 10.4.4.1 (Serial0/0) is resync: split horizon changed
*Mar 1 00:14:05.919: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 10.4.4.3 (Serial0/0) is resync: split horizon changed
R4(config-if)#

Now we see all the routes on R1 and R3.

R1(config-router)#do show ip route eigrp
3.0.0.0/32 is subnetted, 1 subnets
D 3.3.3.3 [90/2809856] via 10.4.4.4, 00:00:58, Serial1/0
4.0.0.0/32 is subnetted, 1 subnets
D 4.4.4.4 [90/2297856] via 10.4.4.4, 00:00:07, Serial1/0
R1(config-router)#

R3(config-router)#do show ip route eigrp
1.0.0.0/32 is subnetted, 3 subnets
D 1.1.1.1 [90/2809856] via 10.4.4.4, 00:01:23, Serial1/0
D 1.3.3.3 [90/2809856] via 10.4.4.4, 00:01:23, Serial1/0
D 1.2.2.2 [90/2809856] via 10.4.4.4, 00:01:23, Serial1/0
4.0.0.0/32 is subnetted, 1 subnets
D 4.4.4.4 [90/2297856] via 10.4.4.4, 00:00:32, Serial1/0
R3(config-router)#

Get access to over 5 hours of IT webinar videos as well as regular study tips and ideas when you
join our mailing list

About This Site

We replaced this site some time ago with an upgraded version. Please feel free to enjoy the content and if you like what you see check out our brilliant new site:

howtonetwork.com

Keep In Touch

About Us

This is a free access website which has now been replaced by howtonetwork.com.

Navigation

  • Home
  • Join
  • Downloads
  • About Us
  • Whitepapers
  • Feature Articles
  • Helpdesk
  • FAQ
  • Free Training

Copyright

All content is protected by international copyright laws. Copyright Reality Press Ltd.

Copyright © 2023 · Dynamik Website Builder on Genesis Framework · WordPress · Log in