Discovery: SNMP Devices Not Scanned by Shazzam When Use SNMP Version Is Set to v1/v2cIssue <!-- /*NS Branding Styles*/ --> .ns-kb-css-body-editor-container { p { font-size: 12pt; font-family: Lato; color: var(--now-color--text-primary, #000000); } span { font-size: 12pt; font-family: Lato; color: var(--now-color--text-primary, #000000); } h2 { font-size: 24pt; font-family: Lato; color: var(--now-color--text-primary, black); } h3 { font-size: 18pt; font-family: Lato; color: var(--now-color--text-primary, black); } h4 { font-size: 14pt; font-family: Lato; color: var(--now-color--text-primary, black); } a { font-size: 12pt; font-family: Lato; color: var(--now-color--link-primary, #00718F); } a:hover { font-size: 12pt; color: var(--now-color--link-primary, #024F69); } a:target { font-size: 12pt; color: var(--now-color--link-primary, #032D42); } a:visited { font-size: 12pt; color: var(--now-color--link-primary, #00718f); } ul { font-size: 12pt; font-family: Lato; } li { font-size: 12pt; font-family: Lato; } img { display: ; max-width: ; width: ; height: ; } } .kb-wrapper { font-family: Lato, sans-serif; font-size: 12pt; line-height: 1.7; color: #000000; max-width: 100%; } .kb-wrapper p { margin: 8px 0; } .kb-wrapper code { font-family: 'Courier New', Courier, monospace; font-size: 10.5pt; background-color: #e6f0f5; color: #032D42; border: 1px solid #b8cfd8; border-radius: 3px; padding: 1px 5px; } Shazzam does not find SNMP port 161 open on some devices when the Use SNMP Version field on a Discovery Schedule is set to v1/v2c, but does find the port open on the same devices when set to All. Symptoms<!-- /*NS Branding Styles*/ --> .ns-kb-css-body-editor-container { p { font-size: 12pt; font-family: Lato; color: var(--now-color--text-primary, #000000); } span { font-size: 12pt; font-family: Lato; color: var(--now-color--text-primary, #000000); } h2 { font-size: 24pt; font-family: Lato; color: var(--now-color--text-primary, black); } h3 { font-size: 18pt; font-family: Lato; color: var(--now-color--text-primary, black); } h4 { font-size: 14pt; font-family: Lato; color: var(--now-color--text-primary, black); } a { font-size: 12pt; font-family: Lato; color: var(--now-color--link-primary, #00718F); } a:hover { font-size: 12pt; color: var(--now-color--link-primary, #024F69); } a:target { font-size: 12pt; color: var(--now-color--link-primary, #032D42); } a:visited { font-size: 12pt; color: var(--now-color--link-primary, #00718f); } ul { font-size: 12pt; font-family: Lato; } li { font-size: 12pt; font-family: Lato; } img { display: ; max-width: ; width: ; height: ; } } .kb-wrapper { font-family: Lato, sans-serif; font-size: 12pt; line-height: 1.7; color: #000000; max-width: 100%; } .kb-wrapper p { margin: 8px 0; } .kb-wrapper ul { margin: 8px 0 8px 24px; padding: 0; } .kb-wrapper li { margin-bottom: 4px; } .kb-wrapper code { font-family: 'Courier New', Courier, monospace; font-size: 10.5pt; background-color: #e6f0f5; color: #032D42; border: 1px solid #b8cfd8; border-radius: 3px; padding: 1px 5px; } Shazzam does not find SNMP port 161 open when Use SNMP Version is set to v1/v2c on the Discovery Schedule.The same devices are successfully scanned by Shazzam when Use SNMP Version is set to All.Working credentials for the affected devices are SNMP v1/v2c community string credentials. Facts<!-- /*NS Branding Styles*/ --> .ns-kb-css-body-editor-container { p { font-size: 12pt; font-family: Lato; color: var(--now-color--text-primary, #000000); } span { font-size: 12pt; font-family: Lato; color: var(--now-color--text-primary, #000000); } h2 { font-size: 24pt; font-family: Lato; color: var(--now-color--text-primary, black); } h3 { font-size: 18pt; font-family: Lato; color: var(--now-color--text-primary, black); } h4 { font-size: 14pt; font-family: Lato; color: var(--now-color--text-primary, black); } a { font-size: 12pt; font-family: Lato; color: var(--now-color--link-primary, #00718F); } a:hover { font-size: 12pt; color: var(--now-color--link-primary, #024F69); } a:target { font-size: 12pt; color: var(--now-color--link-primary, #032D42); } a:visited { font-size: 12pt; color: var(--now-color--link-primary, #00718f); } ul { font-size: 12pt; font-family: Lato; } li { font-size: 12pt; font-family: Lato; } img { display: ; max-width: ; width: ; height: ; } } .kb-wrapper { font-family: Lato, sans-serif; font-size: 12pt; line-height: 1.7; color: #000000; max-width: 100%; } .kb-wrapper p { margin: 8px 0; } .kb-wrapper ul { margin: 8px 0 8px 24px; padding: 0; } .kb-wrapper li { margin-bottom: 4px; } .kb-wrapper code { font-family: 'Courier New', Courier, monospace; font-size: 10.5pt; background-color: #e6f0f5; color: #032D42; border: 1px solid #b8cfd8; border-radius: 3px; padding: 1px 5px; } Because SNMP is a stateless UDP protocol, Shazzam tests whether port 161 is open by sending an SNMP OID request to the device. The device only needs to reply — regardless of success or failure — for the port to be considered open.When Use SNMP Version is set to All, Shazzam sends both an SNMP v1/v2c GetNext request and an SNMP v3 GetNext request.When Use SNMP Version is set to v1/v2c, Shazzam sends only an SNMP v1/v2c GetNext request.Some SNMP devices are configured to not reply to GetNext requests over SNMP v1/v2c, and will only respond to GetBulk or GetScalar requests. These devices will reply to the v3 GetNext sent when All is selected, but not to the v1/v2c GetNext sent when v1/v2c is selected. Release<!-- /*NS Branding Styles*/ --> .ns-kb-css-body-editor-container { p { font-size: 12pt; font-family: Lato; color: var(--now-color--text-primary, #000000); } span { font-size: 12pt; font-family: Lato; color: var(--now-color--text-primary, #000000); } h2 { font-size: 24pt; font-family: Lato; color: var(--now-color--text-primary, black); } h3 { font-size: 18pt; font-family: Lato; color: var(--now-color--text-primary, black); } h4 { font-size: 14pt; font-family: Lato; color: var(--now-color--text-primary, black); } a { font-size: 12pt; font-family: Lato; color: var(--now-color--link-primary, #00718F); } a:hover { font-size: 12pt; color: var(--now-color--link-primary, #024F69); } a:target { font-size: 12pt; color: var(--now-color--link-primary, #032D42); } a:visited { font-size: 12pt; color: var(--now-color--link-primary, #00718f); } ul { font-size: 12pt; font-family: Lato; } li { font-size: 12pt; font-family: Lato; } img { display: ; max-width: ; width: ; height: ; } } All Releases Cause<!-- /*NS Branding Styles*/ --> .ns-kb-css-body-editor-container { p { font-size: 12pt; font-family: Lato; color: var(--now-color--text-primary, #000000); } span { font-size: 12pt; font-family: Lato; color: var(--now-color--text-primary, #000000); } h2 { font-size: 24pt; font-family: Lato; color: var(--now-color--text-primary, black); } h3 { font-size: 18pt; font-family: Lato; color: var(--now-color--text-primary, black); } h4 { font-size: 14pt; font-family: Lato; color: var(--now-color--text-primary, black); } a { font-size: 12pt; font-family: Lato; color: var(--now-color--link-primary, #00718F); } a:hover { font-size: 12pt; color: var(--now-color--link-primary, #024F69); } a:target { font-size: 12pt; color: var(--now-color--link-primary, #032D42); } a:visited { font-size: 12pt; color: var(--now-color--link-primary, #00718f); } ul { font-size: 12pt; font-family: Lato; } li { font-size: 12pt; font-family: Lato; } img { display: ; max-width: ; width: ; height: ; } } .kb-wrapper { font-family: Lato, sans-serif; font-size: 12pt; line-height: 1.7; color: #000000; max-width: 100%; } .kb-wrapper p { margin: 8px 0; } .kb-wrapper code { font-family: 'Courier New', Courier, monospace; font-size: 10.5pt; background-color: #e6f0f5; color: #032D42; border: 1px solid #b8cfd8; border-radius: 3px; padding: 1px 5px; } The affected SNMP device is configured to not reply to GetNext requests over SNMP v1/v2c, but does reply to GetNext requests over SNMP v3. When Use SNMP Version is set to All, Shazzam's SNMP v3 GetNext request receives a response and the port is detected as open. When set to v1/v2c, only the v1/v2c GetNext is sent, the device does not respond, and the port is not detected. Resolution<!-- /*NS Branding Styles*/ --> .ns-kb-css-body-editor-container { p { font-size: 12pt; font-family: Lato; color: var(--now-color--text-primary, #000000); } span { font-size: 12pt; font-family: Lato; color: var(--now-color--text-primary, #000000); } h2 { font-size: 24pt; font-family: Lato; color: var(--now-color--text-primary, black); } h3 { font-size: 18pt; font-family: Lato; color: var(--now-color--text-primary, black); } h4 { font-size: 14pt; font-family: Lato; color: var(--now-color--text-primary, black); } a { font-size: 12pt; font-family: Lato; color: var(--now-color--link-primary, #00718F); } a:hover { font-size: 12pt; color: var(--now-color--link-primary, #024F69); } a:target { font-size: 12pt; color: var(--now-color--link-primary, #032D42); } a:visited { font-size: 12pt; color: var(--now-color--link-primary, #00718f); } ul { font-size: 12pt; font-family: Lato; } li { font-size: 12pt; font-family: Lato; } img { display: ; max-width: ; width: ; height: ; } } .kb-wrapper { font-family: Lato, sans-serif; font-size: 12pt; line-height: 1.7; color: #000000; max-width: 100%; } .kb-wrapper p { margin: 8px 0; } .kb-wrapper ul { margin: 8px 0 8px 24px; padding: 0; } .kb-wrapper li { margin-bottom: 4px; } .kb-wrapper code { font-family: 'Courier New', Courier, monospace; font-size: 10.5pt; background-color: #e6f0f5; color: #032D42; border: 1px solid #b8cfd8; border-radius: 3px; padding: 1px 5px; } .kb-wrapper .callout-info { border-left: 4px solid #52B8FF; background-color: #e6f4ff; padding: 10px 14px; margin: 14px 0; border-radius: 0 4px 4px 0; } Regardless of whether Use SNMP Version is set to v1/v2c or All, the SNMP - Classify probe triggered after Shazzam also uses GetNext to test SNMP credentials. If the device does not respond to GetNext over v1/v2c, classification will fail even if Shazzam successfully detects the port. Address the underlying device configuration using one of the following options: Configure the SNMP device to reply to GetNext requests over SNMP v1/v2c.Alternatively, configure SNMPv3 credentials for the device so that Discovery can communicate using a protocol the device responds to. Note: Setting Use SNMP Version to All may allow Shazzam to detect the port via the v3 GetNext, but classification will still fail if the device does not respond to v1/v2c GetNext and no SNMPv3 credentials are configured. Related Links<!-- /*NS Branding Styles*/ --> .ns-kb-css-body-editor-container { p { font-size: 12pt; font-family: Lato; color: var(--now-color--text-primary, #000000); } span { font-size: 12pt; font-family: Lato; color: var(--now-color--text-primary, #000000); } h2 { font-size: 24pt; font-family: Lato; color: var(--now-color--text-primary, black); } h3 { font-size: 18pt; font-family: Lato; color: var(--now-color--text-primary, black); } h4 { font-size: 14pt; font-family: Lato; color: var(--now-color--text-primary, black); } a { font-size: 12pt; font-family: Lato; color: var(--now-color--link-primary, #00718F); } a:hover { font-size: 12pt; color: var(--now-color--link-primary, #024F69); } a:target { font-size: 12pt; color: var(--now-color--link-primary, #032D42); } a:visited { font-size: 12pt; color: var(--now-color--link-primary, #00718f); } ul { font-size: 12pt; font-family: Lato; } li { font-size: 12pt; font-family: Lato; } img { display: ; max-width: ; width: ; height: ; } } .kb-wrapper { font-family: Lato, sans-serif; font-size: 12pt; line-height: 1.7; color: #000000; max-width: 100%; } .kb-wrapper p { margin: 8px 0; } .kb-wrapper .related-links a { color: #032D42; text-decoration: underline; } .kb-wrapper .link-disclaimer { font-size: 10pt; font-style: italic; margin: 2px 0 10px 0; color: #444; } SNMP support for Discovery — ServiceNow Documentation SNMP Probes — ServiceNow Documentation