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Understanding Routing Protocols
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Configuring protocols on the router

To learn how this was done, we’ll need to schedule a meeting with Nanna Spacely, who is now extremely busy at Sprockets as the lead network design engineer. After a discussion with Nanna, we learn she made the following configurations on the manufacturing router and data center router.

Diagram of scenario.
Figure 3. Diagram shows the IP connectivity between the manufacturing floor and the data center.

Nanna has provided us with the following configuration from the manufacturing floor router. Although Nanna is a stickler for fault-tolerant networks, which means there is a second router on the manufacturing floor with similar connections, she only provides the configuration for one of these routers. The routers are Cisco routers running Cisco IOS software. Nanna uses the Cisco IOS exec mode command sh run to display the running configuration in her manufacturing floor router.



manfloor1# sh run 

ip routing 

! 

interface FastEthernet 0 

ip address 123.21.1.11 255.255.255.0 

! 

interface FastEthernet 1 

ip address 123.21.5.11 255.255.255.0 

! 

router eigrp 41 

network 123.0.0.0

Likewise, the data center is fault tolerant and uses two backbone routers. We’ll examine only one configuration here.

datacenter1# sh run 

ip routing 

! 

! 

interface FastEthernet 0 

ip address 123.21.1.21 255.255.255.0 

! 

interface TokenRing 1 

ip address 123.21.3.21 255.255.255.0 

! 

router eigrp 41 

network 123.0.0.0

The key points of the configuration of these two routers are that the interfaces are all configured using an IP address scheme. The routing protocol is EIGRP with an autonomous system number of 41. The autonomous system number is a networking scheme that designates a logical networking domain. Routers inside this domain can only communicate with other routers in the same domain or autonomous system. However, routers can be configured to communicate with other routers outside their domain. An example of this would be the Sprockets’ firewall router Nanna plans to implement to allow access to the World Wide Web.

Diagram of using redundant network connections.
Figure 4. Fault-tolerant corporate networks use redundant network connections.

For the moment, all the routers in the Sprockets’ corporate network only communicate with devices in the autonomous system 41. This is a number Nanna used arbitrarily in her network design to identify her autonomous system. Networked devices inside the Sprockets’ corporate network domain can now communicate with each other using IP addressing schemes. Some of these concepts I have left a bit nebulous, such as IP and IP addressing. This will be the subject of our next installment of Networking as a Second Language.

Michael J. Norton is a software engineer at Cisco Systems.

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