If you ever wanted to set up a network manually, you will quickly find how much overhead is required to get PCs, printers, and other network equipment. That’s where dynamic routing protocols come into play although they are helpful I strongly urge you to understand static routing first. (See the post Configure Static Routing) So for today’s post let’s get the foundation of understanding dynamic routing protocols.
By definition a routing protocol is a set of messages, rules and algorithms used by routers for the overall purpose of learning routes to other networks not physically connected to it. (RIP, EIGRP, OSPF, and BGP are all examples of routing protocols! When using a dynamic routing protocol routers learn “dynamically” about other remote networks and automatically add these networks to its routing table. However keep in mind that when compared to static routing, dynamic routing require less administrator overhead but they will use the routers resources like, more RAM, more processing time (CPU), and even the network bandwidth
Although there are several routing protocols each of them have their benefits but they all focus on these key things:
Interior Gateway Protocols are used within a company or organization, once that information leaves the company or organization it moves towards the ISP which would use an Exterior Gateway Protocol EGP. So for the picture above think of the clouds to be the inside of a company or organization and outside of that company or organization the routing protocol would change.
For now let’s stop there because the dynamic routing protocols open another door, like Distance Vector and Link-state routing protocols, and the difference between classful and classless routing protocols along with the different type of administrative distances and metrics, these discussions for another day.
Like always I hope this information was informative and if you have a topic that deals with either ICND1 or ICND2 material let me know by commenting below.
Static routes are not that uncommon they at first need some attention to get set up but after it is working nothing needs to change. A good example of using a static route is with a stub network. A stub network is only accessed by a single router and no other routes are configured so there is only one path the network traffic can take. Notice the picture below and how any traffic going towards the network cloud from the 192.168.1.0 network will always pass the 172.16.5.0 network. Why waste putting a routing protocol here?)
In order to configure a static route you must be in the global configuration mode, the ip route command complete syntax is the following:
ip route prefix mask {ip-address} | interface-type interface-number [ip-address]} [dhcp] [distance] [name next-hop-name] [permanent | track number] [tag tag]
For the CCENT/CCNA the complete syntax is not relevant, let’s use a simpler version of the ip route syntax:
ip route network-address subnet-mask {ip address | exit interface}
The network address is the destination network or the remote address that will be added in the routing table. (For the complete syntax this follows on the prefix parameter)
The subnet mask is the subnet mask of the remote network that will be added in the routing table. (For the complete syntax this follows on the mask parameter)
One or both of the following commands must be configured:
The ip-address in the syntax is usually called the next-hop router’s IP address
The exit-interface is the outgoing interface that would be used in forwarding the packets io the destination network (For the complete syntax this follows on the interface-type
interface-number parameter)
Looking at the picture above we need to have a static route on R2, we can do these in two ways the first example is using the next hop IP address. (For this example the next hop IP address is 172.16.5.1 R1′s serial 0/0/0 interface. The next example is using the exit interface out of R2.
The last thing we need to do in order for this stub network to work is put a default route on R1 because R2 is going to the cloud the (internet or network) any traffic like a web request going to the internet needs to be forwarded to R2. A default route is a route that will match every IP address. Remember that a router does not have every single possible route on the internet or network usually these can be summary routes and default routes. Like on R2 we can do this in two ways, the first example is using the next hop IP address. (For this example the next hop IP address is 172.16.5.2 R2′s serial 0/0/1 interface. The next example is using the exit interface out of R1.
That’s my tutorial for configuring static routes. Static routes do need some overhead but once you get them working you don’t need to even touch it again. You can find more information at Cisco.com and the Cisco Learning Network.
By definition a routing protocol is a set of messages, rules and algorithms used by routers for the overall purpose of learning routes to other networks not physically connected to it. (RIP, EIGRP, OSPF, and BGP are all examples of routing protocols! When using a dynamic routing protocol routers learn “dynamically” about other remote networks and automatically add these networks to its routing table. However keep in mind that when compared to static routing, dynamic routing require less administrator overhead but they will use the routers resources like, more RAM, more processing time (CPU), and even the network bandwidth
Although there are several routing protocols each of them have their benefits but they all focus on these key things:- Learn about networks from other neighboring routers and maintain up-to-date routing information.
- Advertise routing information to neighboring routers and thus discovering remote networks.
- If more than route is possible the router will pick the best route based on its metric.
- If the any one part of the network fails, react by advertising the bad routes and advertise the best available route. (Convergence)
- IGP (Interior Gateway Protocols) A routing protocol that is designed for a single autonomous system. Some common routing protocols classified under IGP are RIP, IGRP, EIGRP, OSPF, IS-IS.
- EGP (Exterior Gateway Protocols) A routing protocol that is designed for use in between autonomous systems. A common routing protocol classified under EGP is BGP.
Interior Gateway Protocols are used within a company or organization, once that information leaves the company or organization it moves towards the ISP which would use an Exterior Gateway Protocol EGP. So for the picture above think of the clouds to be the inside of a company or organization and outside of that company or organization the routing protocol would change.For now let’s stop there because the dynamic routing protocols open another door, like Distance Vector and Link-state routing protocols, and the difference between classful and classless routing protocols along with the different type of administrative distances and metrics, these discussions for another day.
Like always I hope this information was informative and if you have a topic that deals with either ICND1 or ICND2 material let me know by commenting below.Configure Static Routing
Plugging Cisco routers together and hoping they work out of the box is not something you should hope for. A router can learn about networks in two ways, manually from configured static routers which we will talk about today and dynamic routing protocols which will talk about on Wednesday. Let’s get started!Static routes are not that uncommon they at first need some attention to get set up but after it is working nothing needs to change. A good example of using a static route is with a stub network. A stub network is only accessed by a single router and no other routes are configured so there is only one path the network traffic can take. Notice the picture below and how any traffic going towards the network cloud from the 192.168.1.0 network will always pass the 172.16.5.0 network. Why waste putting a routing protocol here?)
In order to configure a static route you must be in the global configuration mode, the ip route command complete syntax is the following:ip route prefix mask {ip-address} | interface-type interface-number [ip-address]} [dhcp] [distance] [name next-hop-name] [permanent | track number] [tag tag]
For the CCENT/CCNA the complete syntax is not relevant, let’s use a simpler version of the ip route syntax:
ip route network-address subnet-mask {ip address | exit interface}
The network address is the destination network or the remote address that will be added in the routing table. (For the complete syntax this follows on the prefix parameter)
The subnet mask is the subnet mask of the remote network that will be added in the routing table. (For the complete syntax this follows on the mask parameter)
One or both of the following commands must be configured:
The ip-address in the syntax is usually called the next-hop router’s IP address
The exit-interface is the outgoing interface that would be used in forwarding the packets io the destination network (For the complete syntax this follows on the interface-type
interface-number parameter)
Looking at the picture above we need to have a static route on R2, we can do these in two ways the first example is using the next hop IP address. (For this example the next hop IP address is 172.16.5.1 R1′s serial 0/0/0 interface. The next example is using the exit interface out of R2.
1 | R2(config)#ip route 192.168.1.0 255.255.255.0 172.16.5.1 |
1 | R2(config)#ip route 192.168.1.0 255.255.255.0 serial 0/0/1 |
1 | R1(config)#ip route 0.0.0.0 0.0.0.0 172.16.5.2 |
1 | R1(config)#ip route 0.0.0.0 0.0.0.0 serial 0/0/0 |
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