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Visual DHCP scope assignment automatically displayed on a WebServer

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Deal Addict
Sep 12, 2007
2952 posts
1061 upvotes

Visual DHCP scope assignment automatically displayed on a WebServer

Anybody know if there is:

1) an app that can be run on a schedule that will to an IP scan of the network of a DHCP scope and give results of what is assigned to what (also vendor name like Softperfect's free IP scanner) and will then ouput a HTML file with the results (and hotlinks to the IPs)?

2) a free small VM appliance that will actually do the above and also provide the web server (let's say under Linux) so that I can just run it, set the network, and I can just browse to it to find out when IPs change, etc.

This is for a testdev/testdemo environment, and using static IPs won't work due to the changing nature of the hardware.

Thanks in advance!
8 replies
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Mar 20, 2009
8862 posts
2693 upvotes
Vancouver
Issuing a DHCP request on the network will get you the subnet range, but I think there are only two ways you could get the current DHCP IP address assignments:

1. Query the router (or DHCP server) to find out what addresses it has assigned. But that's a custom query/response for each router, and it won't tell you about static IP assignments.

2. Scan the local subnet to find out which IP addresses respond. But devices with security settings may not respond to standard port numbers, and that wouldn't distinguish static IPs from those assigned by DHCP.

If I were doing this, I'd probably just write a bit of custom code to fetch the information from my router via http.
Deal Addict
Sep 12, 2007
2952 posts
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Yeah, I don't have the login/guest user to our Cisco router as the person who managed that left and never left us with the login; the only way to get this is to do a password recovery on that router which will reset it to factory settings (PITA). That would be the easiest... ugh...
Deal Addict
Jun 8, 2005
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Toronto
vodka wrote: Yeah, I don't have the login/guest user to our Cisco router as the person who managed that left and never left us with the login; the only way to get this is to do a password recovery on that router which will reset it to factory settings (PITA). That would be the easiest... ugh...
Sounds like you have to balance the time/cost of redoing your router config vs implementing whatever hacky workaround you're trying to do. If not this, another issue may come up one day with your network config that will require making a change that can only be done by accessing the router. Or in other words, if you don't reset the router now, you're kicking the can down the road.

If you can't get in touch with the person who had the password, maybe even buy/build a replacement router. Then you can swap out the old one for the new one, make config changes so that it works, and if everything falls apart, you can always swap back the old one.
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Dec 3, 2003
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Edmonton
vodka wrote: Yeah, I don't have the login/guest user to our Cisco router as the person who managed that left and never left us with the login; the only way to get this is to do a password recovery on that router which will reset it to factory settings (PITA). That would be the easiest... ugh...
Is the "no service password-recovery" set on the router then? If not, you might be able to reset the password and keep the config. In any event, you'll eventually need to make changes, so it's better to go through the pain of gaining access before it's an emergency, in my opinion.
Definition: Than
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Deal Addict
Sep 12, 2007
2952 posts
1061 upvotes
Interesting! I'll ask the Cisco guys to check that!! Thanks for the idea.
Deal Addict
May 26, 2002
1908 posts
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Every Cisco device I've worked with has some way to regain access as long as you have physical access to the device. Typically you'd need a Cisco console cable, issue a break command during bootup. That gets you in the device command prompt without requiring password. You then proceed to load the flash manually to bypass the password, once it's loaded you can change the password in the config file and write back to flash. You can get exact directions from the Cisco website for your particular model, done properly you will not lose your current configuration you'll only change the password to something you know so you can log in.

-LeeBear
Deal Expert
Mar 23, 2004
35606 posts
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I think you need to create a GUI interface, using visual basic, and see if you can track the IP addresses :lol:
Deal Addict
Sep 12, 2007
2952 posts
1061 upvotes
Thanks for your feedback. It happened after some password tries that the l/p was cisco. HA, go figure... all is well, no more issues.

I'm looking at PRTG now, gave this a go in a VM, seems very close to what I'm looking for :)

Cheers!!

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