vpns and old network help

[martinpage23]

afternoon, I have a primary school which has 6 vlans. Its an old network and server etc which i am am trying to keep going as no money to sort just yet. Its my only place with vpns so my knowledge of them is very slight. Can you tell me where the dhcp server puts devices ( ip address) of devices that are not on a vlan? its a fire alarm contact panel that just needs an ip address and allow out side connections for call out. the device has no screen and Chubb and installed it and connected it to a network socket. they know the mac address but can't see what ip it has been given. I have gone through the each dhcp vlan address lease and its not there. any help on this would be great as i am lost..... thanks Edited September 17, 2024 by martinpage23

[simpsonj]

Do you mean vLan rather than VPN?

 

If it's vLan, then it will depend on which vLan is 'untagged' (if HP) or tagged (if Cisco) on the port the Fire Alarm panel is connected to.

 

Essentially:

 

1, Find out which port the Fire Alarm System is connected to

2, Then trace that port back to the cabinet and switch port it's connected to

3, Remote onto the management of that switch

4, Look up what vLan information that port has

 

Alternatively, you could run an IP scanning software (Angry IP Scanner, for example) on each of your IP address ranges and correlate the MAC Address you've been given to the IP address

[martinpage23]

hi thanks for that. ( yes have corrected now lol) . the socket it has been connected to is on a 8 port switch that i guess some one has added but its not a vlan switch, but it is connected to another switch which is a managed switch on the vlan!!!! work that mess out. i did try the angry scanner but it didnt show any mac addresses for anything. thanks so far

[DalekSec]

If a dumb switch is plugged into a managed switch which is on an untagged/access VLAN then the dumb switch will use the VLAN of that port.

 

Find the VLAN ID, go to the router or DHCP server and find what range it's using

[martinpage23]

hi thanks for that. ok will see if i can get to the school and have a look. would have thought that if i went through all the vlans on the dhcp server i should be able to find the mac address still?

thanks

[DalekSec]

First port of call (pun intended) is to find what port and vlan its plugged into then you can work out the rest. Also look at the traffic and activity on the port to see if it is actually being used and data going though it.

[simpsonj]

hi thanks for that. ( yes have corrected now lol) . the socket it has been connected to is on a 8 port switch that i guess some one has added but its not a vlan switch, but it is connected to another switch which is a managed switch on the vlan!!!! work that mess out. i did try the angry scanner but it didnt show any mac addresses for anything. thanks so far

 

Maybe try Advanced IP Scanner, that definitely shows MAC Addresses!

[Davit2005]

What device/appliance/VM is been used as the DHCP server?

 

Also if routing is been done on a core switch it may be possible to look up the mac address table and the arp info for the MAC address.

Edited September 18, 2024 by Davit2005