Unless that switch is configured not to send CDP packets you can use another Cisco device (e.g. a router or another switch) in order to discover its IP address if configured. You must set an IP address to the new Cisco device from the same subnet of the 2900 and connect them. Telnet to the new one and issue SHOW CDP NEIGH DETAIL.
Another way to discover IP address if configured is logging on to that switch via console.
Bear in mind that SHOW CDP NEIG DETAIL always works if any Cisco device is connected to 2900 and is useful to discover IP address of neighboring Cisco devices.
One way Ive used before to identify other devices on a segment is to compare the ARP table entries with the IEEE registration of MAC addresses. The first 3 bytes of the MAC address identify the manufacturer, so if you look up all the possible MAC's for "Cisco" and look in the ARP table to see whats there. You can do some pings to start with to make sure the table is fully loaded.
Of course this doesnt help if there are hundreds of Cisco devices on your segment, or if the device you are looking for is in a different IP range on the same segment, but normally it works a treat (long winded tho.)
I used to work on a lot of networks without CDP. You can tell cant you.... Time for my medication I think....
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...