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Configuration checks for NAC IP resolution issues

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TitleConfiguration checks for NAC IP resolution issues
Symptoms
  • IP resolution fails for host
  • End station does not show up in current role
  • Configuration issues with IP resolution.
Environment
Netsight NAC
Cause
  • Radius accounting is not enabled on switch or wireless controller.
  • SNMP query did not yield results
  • SNMP contact to switch is lost
  • DHCP helper is not pointing to the NAC IP addresses 
Resolution
Radius accounting is listening on NAC on port 1813 for Radius attribute framed-ip to look for changes to role state/user-id for end station. This is taken as most accurate by NAC for IP resolution. Some switches will send the framed-IP also in radius authentication packets, this will not be used by NAC for IP resolution, only when the framed-IP attribute is send in an accounting packet it will be used by NAC.
  • NAC manager --> Switches --> Double click the switch --> make sure RADIUS accounting is enabled.

Make sure SNMP is returned from switch. IpNetToMedia and ctAlias MIBs are used. ctAlias is only supported on some Extreme switches.DHCP is also listened to so it gets to see the full hand shake of client/server. It will not participate in DHCP process but is passively listening to gain knowledge of end station identity. Make sure router's IP-helpers are configured to forward to the NAC IP address.
Right click the NAC --> Webview ---> Status --> Switches and Routers
  •  The switch dynamic information section will indicate if any devices have SNMP contact issues.

DHCP is also listened to so it gets to see the full hand shake of client/server. It will not participate in DHCP process but is passively listening to gain knowledge of end station identity. Make sure router's IP-helpers are configured to forward to the NAC IP address.
 


 
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