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This is a feature request.
When SNMP is enabled the switch automatically opens both UDP and TCP port 161. Only UDP/161 is necessary. N5k(config)#snmp-server protocol enable Leaf3(config)# show sockets connection tcp | i 161 tcp LISTEN 0 *(161) N5k(config)# no snmp-server protocol enable N5k(config)# show sockets connection tcp | i 161 N5k(config)#
There is no workaround other than not using SNMP.
*IANA has reserved TCP/UDP port 161 & 162 for SNMP: https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.txt snmp 161 tcp SNMP snmp 161 udp SNMP snmptrap 162 tcp SNMPTRAP [Marshall_Rose] [Marshall_Rose] snmptrap 162 udp SNMPTRAP [Marshall_Rose] [Marshall_Rose] *There is no requirment to use TCP for SNMP communication; in fact the IEFT recommends UDP transports. Note the following standards documents: http://tools.ietf.org/html/rfc1906 "3. SNMPv2 over UDP This is the preferred transport mapping." http://tools.ietf.org/html/rfc3416 "2.6. Transport Mappings It is important to note that the exchange of SNMPv2 messages requires only an unreliable datagram service, with every message being entirely and independently contained in a single transport datagram. Specific transport mappings and encoding rules are specified elsewhere [5]. However, the preferred mapping is the use of the User Datagram Protocol [6]." https://tools.ietf.org/html/rfc3417 "3. SNMP over UDP over IPv4 This is the preferred transport mapping." *Therefore it is a valid request to prevent TCP/161 from listening when enabling SNMP in this platform. *Note that this discussion does not pertain to SNMP over TLS/DTLS, only to plain text SNMP.
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