Hardware Problems
Hardware problems usually refer to the interface drivers; modules of RAM, processor router, an interface cable connected improperly, and even the fan. If the fan fails, the router will heat up and will reboot (the router does not have to temperatures above 37 degrees). In cases where the router is stopped abnormally, you can use the show stacks command to retrieve the error messages that have been saved in the ROM monitor at the time of detection. Cisco may use the information provided by this command to help you determine the cause of the error. It is also good practice to protect the router against falls and peak power by a UPS.
A failure of the physical components of the router, there may be situations where the router does not have enough RAM or processor to handle the traffic of packets. One of the methods used by managers to identify bottlenecks is to use some type of packet network management software. CiscoWorks is an example of a package of network management software that provides several tools to monitor network interconnections and solve possible problems that may arise.
Interface Issues
If you have a problem with a particular node on a LAN, you can check the LED on the hub to see if it looks like. The LEDs turn on when a particular hub port is connected to a node via a twisted pair cable. If the light does not turn, will mean that either the wrong cable, or hub port is damaged, or the interface of the router or network card connected to that port is not working. Connectivity problems in a LAN, can also be related to the length of the physical network cable, the cable is broken, etc.
The WAN connection devices can also pose problems. If the hardware problem has to do with switching equipment provided by the service provider, little can be done. In many cases, network administrators build fault tolerant systems in the interconnection by configuring redundant connections.
One way to check an interface is to use the show interfaces command. Ethernet-related problems may result from excessive collisions on a network, usually due to breaks in the wire, cables that exceed the maximum permitted length, to excessive broadcast traffic, or malfunctioning of any network card. The command show interfaces [interface] can consult the statistics relating to an interface.
- Ethernet 0 is up, Line Protocol is Up. This means that the interface is activated, and believe that Ethernet protocols can use the line. If the interface is disabled, check the LAN connection with the interface. You can use the shut command (to disable the interface), then no shut command to unlock it.
- Serial 0 is Up, Line Protocol is Up. The parameter is Up Serial 0 indicates that the interface is active. If the interface is disabled, may be due to a problem with the connection between the router and CSU / DSU, such as connecting the cable or phone line. Parameter Line Protocol is Up indicates that the WAN protocols in use believe that the line may be used. If the line protocol is disabled, it may be because the router is incorrectly configured (use the show running-config command), but it could also be a problem in the line or switching equipment supplier.
- Hardware Address. Displays the MAC address.
- Internet Address. Displays IP address and subnet mask.
- MTU. Is the maximum transmission unit for the interface in bytes.
- BW. Corresponds to the bandwidth for the interface expressed in kilobits per second.
- Rely. This is a parameter for assessing the reliability of the line, with maximum reliability 255/255. The reliability is often affected due to cuts in line and other problems.
- Load. This parameter measures the current load that supports the interface, representing a value of 255/255 fully saturated interface.
- Encapsulation. Indicates the frame type assigned to the interface. ARPA is the default for Ethernet, and corresponds to the 802.2 frame type.
- Collisions. Displays the number of collisions controlled by the interface. A large number of collisions indicates that there may be some physical problems in the network, like a cut in a cable or a malfunction of the interface card.
- CRC. For LAN interfaces. This parameter shows the number of cyclic redundancy tests that have failed to inbound packets. Normally indicates if the line is carrying a lot of interference or the serial cable connected to the router CSU / DSU is too long.
- Last input. Number of hours, minutes and seconds since it was successfully received the last packet for an interface. It is useful to know when an interface has failed.
- Output. Number of hours, minutes, and seconds since it was successfully transmitted the last packet for an interface. It is useful to know when an interface has failed.
- 5 minute input rate 5 minute output rate. Input and output speeds of the last five minutes. Possible to obtain approximately half of traffic per second at a particular time.
- Packets input. Total number of packets received without error by the system.
- Bytes input. Total number of bytes, including MAC and data encapsulated in packets received without errors.
- No buffer. Number of packets received that were discarded for not having enough space in the buffer for the interface.
- Runts. Numberof packages that have been discarded because their size is less than the minimum packet size allowed, for example any Ethernet packet less than 64 bytes. They are usually caused by collisions.
- Giants. Number of packages that have been discarded for exceeding the maximum size of package, for example any Ethernet packet larger than 1518 bytes.
You can use a control device known as escape box to determine if you are receiving a signal from the CSU / DSU. Disconnect the CSU / DSU router and connect it to the exhaust box. If there is no signal, the line may not be hired well-connected to CSU / DSU, or does not work.
Protocol Issues
If a workstation can communicate with the machines on your subnet, but not with the other machines on other subnets, check the specific gateway configured on the workstation. You can also use the command show ip route to determine if the router is active for routing. Of course, use the show ip interfaces command to ensure that all router interfaces are configured with an IP address, and be careful in the use of access lists.
If you want the router automatically build its routing table must select a routing protocol. You can use the show running-config command to check if active a routing protocol.
Two very useful tools to check the connections are ping and trace. Ping sends an ICMP echo request with the specified IP address, and if that address receives the packet, passes to respond by returning the package to your home. There is an expanded version of ping command to set the packet size and other parameters. The times are measured by ping in milliseconds. The ping command can also be used when working with IPX and AppleTalk.
Trace allows you to see the route will follow the packages from origin to destination. This can determine if the routers that normally participate in the route is activated or not.
In IPX environments, verify that you use the appropriate version of client software for the server version being used and the frame type of the router, clients and servers, which must be the same in all where if we want communication to occur. You can use the Load Monitor on the NetWare server to check the frame type, and number of client licenses of posts (also could have run out of licenses). Finally, you can use version for ipx ping, ping red.nodo with the syntax.
AppleTalk environments, most problems relate to cable ranges and zone names. Also, if you try to route traffic through an interface where you use AppleTalk Phase 1 and AppleTalk Phase 2, you may experience routing problems. The best thing is to update the routers and other devices that support only the AppleTalk Phase 2. You can also use the ping command to ping red.nodo syntax, and use the debug command. The debug command is very simple, but consumes many resources of the router, such as memory, so you should disable it. To enable debugging execute the command debug apple routing, while for non-stop debug execute all ..
Finally, any network administrator worth his salt will make sure to have an updated network map covering the entire network and that includes the addressing scheme and location of devices such as routers, bridges and servers. Create a map is very simple. The creation tools network diagrams as Visio Standard, facilitate the construction of these diagrams. Other versions of Visio, as Visio Enterprise, provided all the icons you require to represent any and all network devices that are currently marketed, thus creating diagrams understandable for any network administrator.