Can t Get There from Here

Can't Get There from Here

When a segment of your network is down, getting "there" is impossible . Several factors can cause this, depending on how you configure your network. Try to PING different nodes of the network to pinpoint what's down. For example, if you can PING one interface of a router but not the other interface, the problem is probably inside the router. You can also perform a TRACERT (as discussed in Chapter 14) on TCP/IP to determine the time intervals between the current and final destinations. A slow response between two destinations could point you to the exact location of the problem. Try using PING and TRACERT from different locations on your network to further define what can be seen and from where.

Tip 

Use more than one utility to determine where your network failure may be. For example, PING works with the TCP/IP protocol only: Try using another utility, such as NBTSTAT, which works with NetBIOS and TCP/IP.

Also, the following problems could prevent you from accessing portions of the network:

• Router problem: Routers connect different networks. If you've defined your router improperly, you can't see what's on the other side. Routers can also experience congestion and drop packets. In these cases, you may need more memory in the router. Older routers also require chip upgrades; for newer routers, upgrades can be written to the current chips. Check which software version your router is using and contact the manufacturer.

• Bridge problem: If your network contains bridges, sometimes you need to reboot the bridge. This may occur frequently, depending on the software and hardware used. Remember that bridges need high-end NICs because they pass a lot of packets between them. (See Chapter 4 for more information on bridges.)

• WAN link problem: If a T1 or 56 KB line goes down, you don't see anything on the other side of the line. Sometimes, you may have to call a telecom company to resolve this problem. You need to have circuit information and the customer support number handy.

• Hub problem: If you lose an entire segment of the network, check the hub that connects that segment. Hubs usually have power supplies and ports that can go bad. Sometimes, just plugging a node into a different port on the hub corrects a problem. Make sure you mark the port as bad so someone else doesn't plug a device into that port. Putting a circle around the port is often a good way to denote a bad port.

• Wiring problem: Wiring can degrade over time or can be moved around enough that the wires can go bad. Use a Time Domain Reflectometer (TDR) tool to check the cable for breaks. You may have to pull a new cable to the desktop or server. If you suspect that housekeeping has vacuumed over one of your satin cables and damaged it, replace that cable!

• Server problem: Check that the server in question is up and running. This seems obvious, but check it anyway.

• Name resolution problem: You may need to install Windows Internet Naming Service (WINS), DHCP, or a host file, depending on the protocols used on your network. (See Chapter 14 on TCP/IP for more information.)