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I just bought a Linksys SE1500 Ethernet switch and I'm trying to set up a small standalone network for pentesting and security research. However, when I do a network scan with one of the computers using the eth0 interface, nothing happens. DHCP is enabled on all the machines. This may seem trivial but..... should I turn off DHCP and manually assign IP addresses, or should the switch be assigning IP addresses (even though its not)?

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can you piing from windows to the linux systenm? Have you looked to see whether ip addresses are on both systems? Are there link lights on both systems? –  Mike Pennington Aug 5 '12 at 6:10
    
If by link lights you mean the lights on the switch ports then yes the switch is recognizing each machine. The windows machine has the automatic ip address 169.254.x.x and the linux machines do not have any ip addresses at all. So I cannot ping anything. When I tried to ping the 169.254.x.x address from a linux machine, I got a connect: Network is unreachable error. –  ridecontrol53 Aug 5 '12 at 6:14
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A switch should not assign IP addresses. A switch shouldn't do anything at the IP level. Switches are Ethernet things, not IP/Internet things. –  David Schwartz Aug 5 '12 at 8:06
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@DavidSchwartz, that depends on whether you are dealing with a true L2 switch, or a multi-layer switch. Multi-layer switches issue DHCP all the time. –  Mike Pennington Aug 5 '12 at 8:42
    
@MikePennington: True, but here we are dealing with a true L2 switch. –  David Schwartz Aug 5 '12 at 8:48

2 Answers 2

up vote 1 down vote accepted

There's nothing in the spec of that switch that says it is a DHCP server, so I suspect your problem is that you don't have one at all.

Only the home/very small business switch/router products that act as your internet gateway as well as a switch tend to come with a DHCP server, so the lack of one on something that claims to be a proper dedicated switch should come as no surprise.

Any DHCP server should be able to serve DHCP to any client (e.g. you don't need a "windows DHCP server" and an "Apple DHCP server" and a "Linux DHCP server", just a DHCP server, so the good news is that this should be easy to fix by getting DHCP running on your Linux box. Or just using Static IPs, which might not be "best practice" but is hardly going to matter on the sort of network one can make with a SE1500 switch.

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makes sense. thanks –  ridecontrol53 Aug 5 '12 at 6:35

DHCP clearly isnt working right now... you should either assign statics (the quickest path), or run ISC dhcpd on ubuntu.

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Thats what I thought. I've never set up the ISC DHCP service. It appears as though it only works with Linux/UNIX based systems. Is this true or will it be able to assign an IP to the Windows machines? –  ridecontrol53 Aug 5 '12 at 6:23
    
yes, in fact the ISC dhcpd running on my server at home assigns addresses to windows every day. –  Mike Pennington Aug 5 '12 at 6:53

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