First, let me say that I don't know a lot about networks, so forgive me if I'm asking a stupid question. The apartment complex where I work recently upgraded their network equipment, and when they finished, the two computers in the community computer room no longer had internet access. I took a look at the setup, and it appears to me that the two computers in the office are plugged into two ports on a Cisco PIX 501 Firewall. Those computers still have internet access. A third port has a Linksys 5 Port Workgroup Switch plugged into it, with the two community computer room computers plugged into it. These computers can't access the internet.
It seems to me that this configuration wouldn't work. Wouldn't the router in the firewall see the two computers plugged into the switch as one device asking to be assigned two ip addresses? Wouldn't this screw things up? Or am I way off base here? Thanks for any input.
George Jetson wrote in news:Xns97B8CB27D47EEgeorgegureachcom@140.99.99.130:
Nope, the switch should not interfere at all. Without more information, it's almost impossible to identify where the real problem lies. You say they "upgraded" the network. What does that mean? Is the PIX new? Did someone add in more computers? New ISP?
As a starting point, I would recommend looking at the TCP/IP properties for the computers that have internet access and the ones without. I suspect you will find a difference there. Pay attention to whether they are using static or dynamic IP addresses inside your LAN, the Gateway IP address in use and possibly the DNS server IP addresses.
Rick wrote in news:Xns97B8CD19A9D50rlsomewhere@69.28.186.121:
They got rid of a Linksys router and replaced it with the Cisco firewall and the Linksys workgroup switch. The computers in the office were plugged directly into the firewall, and the two computers in the computer room were plugged into the workgroup switch, which was then plugged into a single port in the firewall.
That's why I thought it was the configuration of the switch. I didn't think a router could detect two computers on a switch through a single port on the router. I thought it was one computer, one port. Two computers on one port would "confuse" the router, wouldn't it?
George Jetson wrote in news:Xns97B8CECBB2718georgegureachcom@140.99.99.130:
No. The switch will keep things straight between the router and each of the computers. The router shouldn't care whether it is communicating to one computer or a thousand computers through any single port (not considering bandwidth or seat licensing issues). This kind of router/firewall/switch combo is common in small offices.
Far more likely is that the PIX uses a different IP address for it's LAN side than the Linksys did and the two computers in the commons area did not have their gateway address properly updated, or the LAN was reconfigured to use static IP addresses within the LAN and the two computers in the commons area were not changed over from DHCP. There are other possibilities including deliberate configurations to deny internet access to those computers, a change in ISP with different DNS server settings, etc. Best bet is to talk to whoever set up the new network. This sounds far more like an inadvertent or deliberate configuration problem.
Rick wrote in news:Xns97B8E32287A2Arlsomewhere@69.28.186.121:
Thanks for the info. I work in the maintenance dept. at the apt complex. Someone from the main office on the other side of the state came down last Friday to upgrade the equipment, but couldn't get it to work. So he left, with a promise to come back to get it going. He hasn't come back yet. The residents are starting to bug me to get it running again, so I thought I would see if I could at least get one of the computers running. I took a look at the setup, but figured I should know what I was doing before I started unplugging patch cords.
Switches and hubs work on a seperate layer of the network. They work with Mac addresses (well the switch does), where- as routers work on a higher layer (the IP address).
Do the following.
(1) Open a command prompt (cmd.exe). (2) Type IPCONFIG /RELEASE * (3) Type IPCONFIG /RENEW * (4) Type IPCONFIG /ALL
The IPCONFIG /RELEASE * tells the computer to release the IP address configured. Sometimes network cards assign a bogus IP address instead of 0.0.0.0. So we want to see 0.0.0.0 or a valid IP address. The IPCONFIG /RENEW will tell you if the computer is getting a valid IP address.
If all the computers are getting IP addresses from the router, then you'll likely see something like:
10.x.x.x for each computer where x can represent any number between 0 and 255. Feel free to post back with the results of the IPCONFIG /RENEW. IP numbers should be okay to post, but I'd avoid posting the MAC address which appears similar to: 00-00-00-00-00-00 (six two character digits representing hexadecimal addresses).
When things get sent from a computer to another computer, an application creates a packet to send to another system and starts building a list of information so the packet can return properly. The application adds whatever data it needs, then moves down adds the routing information, then the IP address, then the MAC address, then sends it out to the switch which sends the data directly to the router. This brings up a point whereby one port on the switch provides a way to uplink to a modem or router. So that's possibly something you need to check. Perhaps you're plugged into an uplink where you should be plugged into a downlink. Typically the uplinks allow you to stack switches to allow for more connections. Usually one port on the farthest right or left is an uplink port.
When a switch gets a packet of information it only looks at the MAC address and routes it to the appropriate system based upon the MAC address. When a router gets a packet it looks at the IP address of the package to get delivered. They're two totally different layers, switches handling MAC addresses and routers handling IP addresses.
A switch gets confused if two network cards hook up to it with the same MAC address.
A router gets confused if two systems have the same IP address.
Personally, I'd check to see which cable is plugged into the uplink port on the switch and check that out.
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