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© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public ITE PC v4.0 Chapter 1 1 Static Routing Routing Protocols and Concepts – Chapter 2 Sandra Coleman,

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Presentation on theme: "© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public ITE PC v4.0 Chapter 1 1 Static Routing Routing Protocols and Concepts – Chapter 2 Sandra Coleman,"— Presentation transcript:

1 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public ITE PC v4.0 Chapter 1 1 Static Routing Routing Protocols and Concepts – Chapter 2 Sandra Coleman, CCNA, CCAI

2 ITE PC v4.0 Chapter 1 2 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Interfaces  Examining Router Interfaces - Show IP route– used to view routing table -Show Interfaces command – used to show status of an interface and details about it -Show IP Interface brief command – BEST ONE to use to quickly find the status of interfaces and IP addresses! -Show running-config command – used to show configuration file in RAM (can be show run)

3 ITE PC v4.0 Chapter 1 3 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Interfaces  Configuring an Ethernet interface -By default all serial and Ethernet interfaces are down -To enable an interface use the No Shutdown command

4 ITE PC v4.0 Chapter 1 4 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Interfaces  Verifying Ethernet interface -Show interface fastEthernet 0/0 – command used to show status of fast Ethernet port -Show ip interface brief – see status of lines and IP addresses -Show running-config  Ethernet interfaces participate in ARP

5 ITE PC v4.0 Chapter 1 5 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Interfaces  Configuring a Serial interface -Enter interface configuration mode -Enter in the ip address and subnet mask -Enter in the no shutdown command  Example: -R1(config)#interface serial 0/0 -R1(config-if)#ip address R1(config-if)#no shutdown

6 ITE PC v4.0 Chapter 1 6 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Routing Tables  The main purpose of a routing table is to provide the router with paths to different destination networks.  Remember, routers need to know how to get to the NETWORK the packet is on.  It is the switch’s job to get to the exact IP address!  To remove a directly connected network from a router, use these two commands: shutdown and no ip address.

7 ITE PC v4.0 Chapter 1 7 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Debug commands  Purpose of the debug ip routing command  Allows you to view changes that the router performs when adding or removing routes  Example: -R2#debug ip routing -IP routing debugging is on  Debug commands, especially the debug all command, should be used sparingly. These commands can disrupt router operations.  Debug commands are useful when configuring or troubleshooting a network; however, they can make intensive use of CPU and memory resources.

8 ITE PC v4.0 Chapter 1 8 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Routing Table  When a router only has its interfaces configured & no other routing protocols are configured then: -The routing table contains only the directly connected networks -Only devices on the directly connected networks are reachable

9 ITE PC v4.0 Chapter 1 9 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Routing Table

10 ITE PC v4.0 Chapter 1 10 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Reading routing tables (pg. 97-example)  the address must match the number of left-most bits of the network address as indicated by the prefix of the route. For R2, all the routes have a /24 prefix, therefore, the left-most 24 bits are checked for each route.

11 ITE PC v4.0 Chapter 1 11 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Routing Table and CDP Protocol  Checking each route in turn The ping command is used to check end to end connectivity

12 ITE PC v4.0 Chapter 1 12 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public CDP – Cisco Discovery Protocol  Cisco Discovery Protocol (CDP) is a powerful network monitoring and troubleshooting tool.  CDP is an information-gathering tool used by network administrators to get information about directly connected Cisco devices.  CDP is a proprietary tool that enables you to access a summary of protocol and address information about Cisco devices that are directly connected.  By default, each Cisco device sends periodic messages, which are known as CDP advertisements, to directly connected Cisco devices. These advertisements contain information such as the types of devices that are connected, the router interfaces they are connected to, the interfaces used to make the connections, and the model numbers of the devices.

13 ITE PC v4.0 Chapter 1 13 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public CDP Protocol  Purpose of CDP A layer 2 cisco proprietary tool used to gather information about other directly connected Cisco devices.  Concept of neighbors -2 types of neighbors  Layer 3 neighbors  Layer 2 neighbors

14 ITE PC v4.0 Chapter 1 14 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Routing Table and CDP Protocol  CDP show commands  Show cdp neighbors command -Displays the following information:  Neighbor device ID  Local interface  Holdtime value, in seconds  Neighbor device capability code  Neighbor hardware platform  Neighbor remote port ID  Show cdp neighbors detail command -Useful in determining if an IP address configuration error (I have had to use this on the CCNA test several times to find addresses to connecting devices that were not CLICKABLE)

15 ITE PC v4.0 Chapter 1 15 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Routing Table and CDP Protocol  CDP starts up automatically and allows the device to detect directly connected neighbors  Devices can learn about each other REGARDLESS of the routing protocol being used.  Disabling CDP To disable CDP globally use the following command Router(config)#no cdp run To stop CDP advertisements on a particular interface, use the following command: Router(config-if)#no cdp enable

16 ITE PC v4.0 Chapter 1 16 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Learning routes  Static Manually configured by network admin  Dynamic From a dynamic routing protocol (from a neighbor)

17 ITE PC v4.0 Chapter 1 17 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Static Routes  Purpose of a static route A manually configured route used when routing from a network to a stub network (network accessed by a single route) Only one way out of R1 for sending non-local traffic, so it would be a waste of resources to run a routing protocol between R1 and R2 – set up a static route on R2 to the LAN on R1.

18 ITE PC v4.0 Chapter 1 18 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Static Routes  IP route command  To configure a static route use the following command: ip route  Example: -Router(config)# ip route network-address subnet-mask {ip- address | exit-interface }

19 ITE PC v4.0 Chapter 1 19 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Static Routes  Dissecting static route syntax  ip route - Static route command  – Destination network address  Subnet mask of destination network  Serial 0/0/0 interface IP address on R2, which is the "next-hop" to this network

20 ITE PC v4.0 Chapter 1 20 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Static Routes  Configuring routes to 2 or more remote networks  (on test…choose correct command) Use the following commands for R1 -R1(config)#ip route R1(config)#ip route

21 ITE PC v4.0 Chapter 1 21 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Static routes Referring to the graphic, you can see that static routes have an administrative distance of 1 and a metric of 0

22 ITE PC v4.0 Chapter 1 22 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Static Routes  Zinin’s 3 routing principles  Principle 1: "Every router makes its decision alone, based on the information it has in its own routing table.“  Principle 2: "The fact that one router has certain information in its routing table does not mean that other routers have the same information.“  Principle 3: "Routing information about a path from one network to another does not provide routing information about the reverse, or return path."

23 ITE PC v4.0 Chapter 1 23 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Static Routes with Exit Interfaces  Using Zinin’s 3 routing principles, how would you answer the following? -Would packets from PC1 reach their destination? Yes, packets destined for /24 and /24 networks would reach their destination. -Does this mean that any packets from these networks destined for /24 network will reach their destination? No, because neither R2 nor R3 router has a route to the /24 network.

24 ITE PC v4.0 Chapter 1 24 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Static Routes with Exit Interfaces  Configuring a Static route with an Exit Interface -Static routes configured with an exit interface are more efficient because the routing table can resolve the exit interface in a single search instead of 2 searches NO RECURSIVE LOOKUPS REQUIRED! -Example of syntax require to configure a static route with an exit interface

25 ITE PC v4.0 Chapter 1 25 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Resolving an exit interface  What if an interface goes down?  If the static route can NOT be resolved, it is REMOVED from the routing table!

26 ITE PC v4.0 Chapter 1 26 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Static routes  Find this line in the routing table: S /24 is directly connected, Serial0/0/0  Now, when the routing table process has a match for a packet and this static route, it will be able to resolve the route to an exit interface in a single lookup. As you can see in the figure, the other two static routes still must be processed in two steps, resolving to the same Serial 0/0/0 interface.

27 ITE PC v4.0 Chapter 1 27 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Static Routes  Modifying Static routes  Existing static routes cannot be modified. The old static route must be deleted by placing no in front of the ip route  Example: -no ip route  A new static route must be rewritten in the configuration

28 ITE PC v4.0 Chapter 1 28 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public When to alter routes!  A network admin might need to alter a static route if A destination network no longer exists Next-hop address or exit interface becomes inaccessible

29 ITE PC v4.0 Chapter 1 29 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Static Routes with Exit Interfaces  Verifying the Static Route Configuration -Use the following commands  Step 1 show running-config  Step 2 verify static route has been entered correctly  Step 3 show ip route  Step 4 verify route was configured in routing table  Step 5 issue ping command to verify packets can reach destination and that Return path is working

30 ITE PC v4.0 Chapter 1 30 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Static Routes with Exit Interfaces  Ethernet interfaces and ARP. – If a static route is configured on an Ethernet link -If the packet is sent to the next-hop router then… the destination MAC address will be the address of the next hop’s Ethernet interface A router CANNOT determine the next-hop MAC address for a frame without a next-hop address on the Static route

31 ITE PC v4.0 Chapter 1 31 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Solution to Ethernet interfaces  Is there any way to configure a static route over an Ethernet network so that it does not have to use the recursive lookup of the next-hop IP address? Yes - this can be done by configuring the static route to include both the exit interface and the next-hop IP address.  As you can see in the previous figure, the exit interface would be FastEthernet 0/1 and the next-hop IP address would be  R1(config)#ip route fastethernet 0/  The routing table entry for this route would be:  S /24 [1/0] via FastEthernet0/1  The routing table process will only need to perform a single lookup to get both the exit interface and the next-hop IP address.

32 ITE PC v4.0 Chapter 1 32 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Summary and Default Route  Summarizing routes reduces the size of the routing table.  Route summarization is the process of combining a number of static routes into a single static route.

33 ITE PC v4.0 Chapter 1 33 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Calculating Summary routes (on test!)  1. Write out the networks that you want to summarize in binary.  2. To find the subnet mask for summarization, start with the left-most bit.  3. Work your way to the right, finding all the bits that match consecutively.  4. When you find a column of bits that do not match, stop. You are at the summary boundary.  5. Now, count the number of left-most matching bits, which in our example is 22. This number becomes your subnet mask for the summarized route, /22 or  6. To find the network address for summarization, copy the matching 22 bits and add all 0 bits to the end to make 32 bits.

34 ITE PC v4.0 Chapter 1 34 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Summary and Default Route  Configuring a summary route Step 1: Delete the current static route Step 2: Configure the summary static route Step 3: Verify the new static route You will have to do this on the Chapter 2 onlineTest!

35 ITE PC v4.0 Chapter 1 35 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Summary and Default Route  Default Static Route  This is a route that will match all packets. Stub routers that have a number of static routes all exiting the same interface are good candidates for a default route. -Like route summarization this will help reduce the size of the routing table  Configuring a default static route (know this!)  Similar to configuring a static route. Except that destination IP address and subnet mask are all zeros  Example: -Router(config)#ip route [exit-interface | ip- address ]

36 ITE PC v4.0 Chapter 1 36 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Summary and Default Route  Static routes and subnet masks The routing table lookup process will use the most specific match (the one with the MOST # of bits in common with the packet – look at the CIDR notation to see which one is the closest match – that’s what determines how many bits must match) when comparing destination IP address and subnet mask  Default static routes and subnet masks Since the subnet mask used on a default static route is all packets will match. Default routes are VERY COMMON. Instead of having to store many routes for all the networks on the Internet, the can store a single default route to represent ANY network not in the routing table.

37 ITE PC v4.0 Chapter 1 37 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Finding the BEST route in the routing table  It is possible that the destination IP address of a packet will match multiple routes in the routing table. For example, what if we had the following two static routes in the routing table:  /24 is subnetted, 3 subnets  S is directly connected, Serial0/0/0 and  S /16 is directly connected, Serial0/0/1  Consider a packet with the destination IP address This IP address matches both routes.  The routing table lookup process will use the most-specific match. Because 24 bits match the /24 route, and only 16 bits of the /16 route match, the static route with the 24 bit match will be used. This is the longest match.  The packet will then be encapsulated in a Layer 2 frame and sent via the Serial 0/0/0 interface. Remember, the subnet mask in the route entry is what determines how many bits must match the packet's destination IP address for this route to be a match.

38 ITE PC v4.0 Chapter 1 38 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Static Routes and Packet Forwarding  Packet forwarding with static routes. (recall Zinin’s 3 routing principles)  Router 1 Packet arrives on R1’s Fastethernet 0/0 interface R1 does not have a route to the destination network, /24 R1 uses the default static route.

39 ITE PC v4.0 Chapter 1 39 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Static Routes and Packet Forwarding  Packet forwarding with static routes. (recall Zinin’s 3 routing principles)  Router 2 The packet arrives on the Serial 0/0/0 interface on R2. R2 has a static route to /24 out Serial0/0/1.

40 ITE PC v4.0 Chapter 1 40 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Static Routes and Packet Forwarding  Packet forwarding with static routes. (recall Zinin’s 3 routing principles)  Router 3 The packet arrives on the Serial0/0/1 interface on R3. R3 has a connected route to /24 out Fastethernet 0/1.

41 ITE PC v4.0 Chapter 1 41 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Static Routes and Packet Forwarding  Troubleshooting a Missing Route  Tools that can be used to isolate routing problems include: -Ping– tests end to end connectivity -Traceroute– used to discover all of the hops (routers) along the path between 2 points -Show IP route– used to display routing table & ascertain forwarding process -Show ip interface brief- used to show status of router interfaces -Show cdp neighbors detail– used to gather configuration information about directly connected neighbors

42 ITE PC v4.0 Chapter 1 42 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Static Routes and Packet Forwarding  Solving a Missing Route  Finding a missing or mis-configured route requires methodically using the correct tools -Start with PING. If ping fails then use traceroute to determine where packets are failing to arrive  Issue: show ip route to examine routing table. -If there is a problem with a mis-configured static route remove the static route then reconfigure the new static route

43 ITE PC v4.0 Chapter 1 43 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Static Routes and Packet Forwarding  Solving a Missing Route

44 ITE PC v4.0 Chapter 1 44 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Static Routes and Packet Forwarding  Solving a Missing Route

45 ITE PC v4.0 Chapter 1 45 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Ch. 2 is history, Now let’s have some fun in the labs! Study Guide – Homework Pg – Calculating Summary Route Exercises Summary Route exercise #1, 2, 4, 5, 6 Labs – Lab 2-2, pg. 119 – we will subnet this FIRST in the lab today, then you can do it on the actual equipment next class meeting. Lab 2-1, page , do this on packet tracer, filename is LSG02-Lab281.pka There are LOTS of packet tracer activities in the textbook and in the lab book… if you don’t understand, for HEAVEN’s sake…use these. I wish we had time during class to do EVERY ONE of them.. We just don’t. I highly recommend you use them. Online test – Take the online test by Sunday, Jan 27, 2013 midnight! Test – TBD – we’ll see how the labs go. For extra credit, Packet Tracer Skills Integration Challenge on page 134 in the lab book. Do this on your own time. You can me or show me the answer 100% complete. I will use this to take the place of another lab grade that you may be missing (now or in the future!)


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