Home > Articles > Cisco Network Technology > General Networking > Cisco Networking Academy's Introduction to Static Routing

Cisco Networking Academy's Introduction to Static Routing

  • Sample Chapter is provided courtesy of Cisco Press.
  • Date: Mar 27, 2014.

Chapter Description

This chapter explains the types of static routes as well as the advantages and disadvantages of each type. It also addresses routing configuration and troubleshooting.

Troubleshoot Static and Default Route Issues (2.5)

Now that you have learned how to configure different types of static routes, this section discusses how to troubleshoot some of the common problems you might encounter. Troubleshooting exercises are an excellent method to help better understand network protocols and configurations. When a static route is no longer needed, that static route should be deleted from the running and startup configuration files.

Packet Processing with Static Routes (2.5.1)

Now that you have configured static routes, you need to learn about the process that a packet goes through as it is forwarded by a router.

Static Routes and Packet Forwarding (

The following example describes the packet forwarding process with static routes.

Examine Figure 2-69, where PC1 is sending a packet to PC3:

  1. The packet arrives on the FastEthernet 0/0 interface of R1.
  2. R1 does not have a specific route to the destination network,; therefore, R1 uses the default static route.
  3. R1 encapsulates the packet in a new frame. Because the link to R2 is a point-to-point link, R1 adds an “all 1s” address for the Layer 2 destination address.
  4. The frame is forwarded out of the Serial 0/0/0 interface. The packet arrives on the Serial 0/0/0 interface on R2.
  5. R2 de-encapsulates the frame and looks for a route to the destination. R2 has a static route to out of the Serial 0/0/1 interface.
  6. R2 encapsulates the packet in a new frame. Because the link to R3 is a point-to-point link, R2 adds an “all 1s” address for the Layer 2 destination address.
  7. The frame is forwarded out of the Serial 0/0/1 interface. The packet arrives on the Serial 0/0/1 interface on R3.
  8. R3 de-encapsulates the frame and looks for a route to the destination. R3 has a connected route to out of the FastEthernet 0/0 interface.
  9. R3 looks up the ARP table entry for to find the Layer 2 Media Access Control (MAC) address for PC3. If no entry exists, R3 sends an Address Resolution Protocol (ARP) request out of the FastEthernet 0/0 interface, and PC3 responds with an ARP reply, which includes the PC3 MAC address.
  10. R3 encapsulates the packet in a new frame with the MAC address of the FastEthernet 0/0 interface as the source Layer 2 address and the MAC address of PC3 as the destination MAC address.
  11. The frame is forwarded out of the FastEthernet 0/0 interface. The packet arrives on the network interface card (NIC) interface of PC3.

    Figure 2-69

    Figure 2-69 Static Routes and Packet Forwarding

Troubleshoot IPv4 Static and Default Route Configuration (2.5.2)

Troubleshooting is a skill that develops as you gain experience. It is always best to look for the most obvious and simplest issues first, such as an interface still in shutdown mode or an interface with the wrong IP address. After these items have been verified, begin looking for more complicated possibilities like an error in the static route configuration.

Troubleshooting a Missing Route (

When end-to-end connectivity is a problem, begin by making sure that you can ping your own interface and other devices on your own directly connected networks. When this has been verified, begin testing connectivity to remote networks from other devices.

Networks are subject to forces that can cause their status to change quite often:

  • An interface fails.
  • A service provider drops a connection.
  • Links become oversaturated.
  • An administrator enters a wrong configuration.

When there is a change in the network, connectivity may be lost. Network administrators are responsible for pinpointing and solving the problem. To find and solve these issues, a network administrator must be familiar with tools to help isolate routing problems quickly.

Common IOS troubleshooting commands include:

  • ping
  • traceroute
  • show ip route
  • show ip interface brief
  • show cdp neighbors detail

Figure 2-70 displays the result of an extended ping from the source interface of R1 to the LAN interface of R3. An extended ping is when the source interface or source IP address is specified.

Figure 2-70

Figure 2-70 Extended Ping

The following output displays the result of a traceroute from R1 to the R3 LAN:

R1# traceroute
Type escape sequence to abort.
Tracing the route to
VRF info: (vrf in name/id, vrf out name/id)
  1 4 msec 4 msec 8 msec
  2 12 msec 12 msec *

The following output displays the routing table of R1:

R1# show ip route | begin Gateway
Gateway of last resort is not set is variably subnetted, 5 subnets, 2 masks
S [1/0] via
C is directly connected, Serial0/0/0
L is directly connected, Serial0/0/0
C is directly connected, GigabitEthernet0/0
L is directly connected, GigabitEthernet0/0
S [1/0] via
S [1/0] via

The following output provides a quick status of all interfaces on the router:

R1# show ip interface brief
Interface                  IP-Address      OK? Method Status                Protocol
Embedded-Service-Engine0/0 unassigned      YES unset  administratively down down
GigabitEthernet0/0      YES manual up                    up
GigabitEthernet0/1         unassigned      YES unset  administratively down down
Serial0/0/0            YES manual up                    up
Serial0/0/1                unassigned      YES unset  administratively down down

The show cdp neighbors command in the following output provides a list of directly connected Cisco devices. This command validates Layer 2 (and therefore Layer 1) connectivity. For example, if a neighbor device is listed in the command output, but it cannot be pinged, then Layer 3 addressing should be investigated.

R1# show cdp neighbors
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
                  S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone,
                  D - Remote, C - CVTA, M - Two-port Mac Relay
Device ID        Local Intrfce     Holdtme    Capability  Platform  Port ID
netlab-cs5       Gig 0/0            156             S I   WS-C2960- Fas 0/1
R2               Ser 0/0/0          153            R S I  CISCO1941 Ser 0/0/0

Solve a Connectivity Problem (

Finding a missing (or misconfigured) route is a relatively straightforward process, if the right tools are used in a methodical manner.

For instance, in this example, the user at PC1 reports that he cannot access resources on the R3 LAN. This can be confirmed by pinging the LAN interface of R3 using the LAN interface of R1 as the source (see Figure 2-71). The results show that there is no connectivity between these LANs.

Figure 2-71

Figure 2-71 Verify Connectivity to the R3 LAN

A traceroute in the following output reveals that R2 is not responding as expected. For some reason, R2 forwards the traceroute back to R1. R1 returns it to R2. This loop would continue until the time to live (TTL) value decrements to zero, in which case, the router would then send an Internet Control Message Protocol (ICMP) Destination Unreachable message to R1.

R1# traceroute
Type escape sequence to abort.
Tracing the route to
VRF info: (vrf in name/id, vrf out name/id)
  1 4 msec 4 msec 8 msec
  2 12 msec 12 msec 12 msec
  3 12 msec 8 msec 8 msec
  4 20 msec 16 msec 20 msec
  5 16 msec 16 msec 16 msec
  6 20 msec 20 msec 24 msec
  7 20 msec

The next step is to investigate the routing table of R2, because it is the router displaying a strange forwarding pattern. Using the show ip route | begin Gateway command, the routing table in the following output reveals that the network is configured incorrectly. A static route to the network has been configured using the next-hop address Using the configured next-hop address, packets destined for the network are sent back to R1. It is clear from the topology that the network is connected to R3, not R1. Therefore, the static route to the network on R2 must use next-hop, not

R2# show ip route | begin Gateway
Gateway of last resort is not set is variably subnetted, 5 subnets, 2 masks
C is directly connected, GigabitEthernet0/0
L is directly connected, GigabitEthernet0/0
C is directly connected, Serial0/0/0
L is directly connected, Serial0/0/0
S 1/0] via is variably subnetted, 2 subnets, 2 masks
C is directly connected, Serial0/0/1
L is directly connected, Serial0/0/1
S [1/0] via

The following shows output from the running configuration that reveals the incorrect ip route statement. The incorrect route is removed and the correct route is then entered.

R2# show running-config | section ip route
ip route
ip route
R2# conf t
Enter configuration commands, one per line.  End with CNTL/Z.
R2(config)# no ip route
R2(config)# ip route

The following output verifies that R1 can now reach the LAN interface of R3. As a last step in confirmation, the user on PC1 should also test connectivity to the LAN.

R1# ping source g0/0
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to, timeout is 2 seconds:
Packet sent with a source address of
Success rate is 100 percent (5/5), round-trip min/avg/max = 28/28/28 ms
7. Summary (2.6) | Next Section Previous Section

Cisco Press Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from Cisco Press and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about Cisco Press products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites; develop new products and services; conduct educational research; and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@ciscopress.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by Cisco Press. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.ciscopress.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020