I faced an interesting problem. So, I have Cisco WS-C2960-48TT-L connected with HP Procurve 2626 and Aruba 2930F switches. when I type "show CDP neighbours" command on the cisco switch I see nothing, but on the other switches, I can see information about the cisco switch. So, I think that my cisco switch can send out CDP messages, but cannot receive. How can I solve this problem?
Ricky Beam's comment is the answer.
The Cisco originates CDP (Cisco Discovery Protocol) because it is Cisco.
HP and Aruba do not originate Cisco Discovery Protocol because they are not Cisco. They probably originate LLDP (Link-Layer Discovery Protocol).
Because HP and Aruba want to be able to sell their products in a Cisco-dominated network industry, they apparently "snoop" the CDP frames and let you see them.
You may need to enable LLDP on your cisco:
config t LLDP run end copy run start
To see LLDP neighbors on your Cisco, use one of the following
show lldp show lldp neighbors
These protocols use L2 multicast. You may get "weird" results if you don't enable one protocol on all devices. Specifically, the CDP or LLDP frames may flood through devices with CDP or LLDP off and be detected by multiple devices on the other side. Easiest way to avoid this in a multi-vendor environment is to enable LLDP on all devices and use "show LLDP" commands consistently.