Switch – How to find IP address of switch

switch

Classic story I.T. guy left now, no documentation indicating config on the switch.

I have Zyxel ES2024 connected to in the middle of the network passing traffic to various VLANs however I cannot get on the switch itself.It looks like management VLAN has been changed, the IP of the switch is problem – the guy was lazy all the switches has standard password. Reset is not an option as I dont have access to console cable here and I cannot really wait to get it delivered.
Any tips, advices greatly appreciated.

Best Answer

You may have some options and without knowing more information, we cannot tell you which way is best.

  1. I agree with Ricky, getting on management VLAN and pinging the broadcast address, looking at your computers ARP table and see which MAC is a Zyxel MAC.
  2. You could run an application like NMAP, maybe even LAN Sweeper, that can scan your management VLAN and give you information about the hosts it can detect.
  3. If the switch has a trunk interface setup, plug your laptop into it and open wire shark, you'll see what VLANs, IPs and MACs are out there
  4. If you have DHCP on the management VLAN or any VLANs, take a look at leases and reservations. If nothing there, look at reserved space.

I would look at DHCP first. If I didn't see a lease or reservation (which I wouldn't expect to see), I would then use the scan tools for the reserved range of IPs in the DHCP scope. The fewer hosts you scan the faster the scan. I would also scan with an ssh username/password (default you said) and that makes me think that the snmp community is also set to "public". Which you could also scan for. I'd also scan for port 443 and 80, as it appears the management Web interface operates on these ports but I'd double check the documentation first and scan those ports.

Happy hunting!

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