Opening port 162 for SNMP instead of only 161

[Vickram]

Hi, i'm tasked to get a ManageEngine(ME) to access Fan information from my switches and routers instead of just me doing a "sh env/ sh env all" on every device CLI. I downloaded the CISCO_ENVMON and CISCO_ACCESS_ENVMON mib files from cisco and my admin tried importing them into her ME. She is only able to obtain CPU info from my devices. 

From my understanding port 161 and 162 is used for SNMP traps. Yet when we tried scanning the ports, only 161 was listening, 162 was closed. I only have the initial and undisturbed SNMP config for these devices done by engineers years before me:

for switches:

snmp-server location <the server location>
snmp-server source-interface traps mgmt0
snmp-server globalEnforcePriv
snmp-server user admin network-admin auth md5 0......
snmp-server user snmpuser network-operator auth sha.....

snmp-server host <her ME host IP>  traps version 3 priv snmpuser
snmp-server host <her ME host IP> use-vrf management

for routers:

snmp-server group snmpgrp v3 priv read ALL-ACCESS access ACL_SNMP_Servers
snmp-server view ALL-ACCESS iso included
snmp-server view ALL-ACCESS mib-2 included
snmp-server view ALL-ACCESS system included
snmp-server trap-source GigabitEthernet0
snmp-server location <server location>
snmp-server enable traps snmp authentication linkdown linkup coldstart warmstart
snmp-server host <her ME host IP> vrf Mgmt-intf version 3 priv snmpuser

I'd really appreciate some help understanding why 162 is closed and how I can open it, as from what I've seen online 161 & 162 are open in default when configuring SNMP

[balaji.bandi]

Port 161 for SNMP

port 162 to send SNMP Trap out.

[Octavian Szolga]

Hi,

You have to differentiate between

• SNMP & UDP 161 - is used for SNMP polling (GET/SET messages)
  • your Network Management System connects to your network device (network device is server in this conversation)
• SNMP & UDP 162 - is used for SNMP traps (SNMP 'notifications')
  • these are sent by your network device to your NMS (your network device is client in this conversation)

Long story short, I don't see why UDP 162 should be open considering that this is a source port (client).

BR,

Octavian