The NAP VSA, MS-IPv4-Remediation-Servers, contains a list of IP addresses that an unhealthy and therefore quarantined supplicant should be allowed access to so that it can remediate itself and become healthy.
The way a quarantine is implemented on the switch is simply by moving the client/port to a user-designated 'quarantine' VLAN whose VLANID/Name is sent in the Access-Accept message. It is up to the user to ensure that the quarantine VLAN does indeed have limited access to the rest of the network. Typically, this can be done by disabling IP forwarding on that VLAN so no routed traffic can get out of that VLAN. Also, with dynamic VLAN creation, the quarantine VLAN being supplied by RADIUS could be dynamically created on the switch, once dynamic VLAN creation is enabled on it. The remediation server(s) would need to be accessible via the uplink port, regardless of whether the quarantine VLAN is pre-configured or dynamically created, since IP forwarding is not enabled on it.
To get around this restriction, network login has been enhanced so when a MS-Quarantine-State attribute is present in the Access-Accept message with extremeSessionStatus being either 'Quarantined' or 'On Probation,' then a 'deny all traffic' dynamic ACL will be applied on the VLAN. If such an ACL is already present on that VLAN, then no new ACL will be applied.
When the last authenticated client has been removed from the quarantine VLAN, then the above ACL will be removed.
Additionally, if the MS-IPv4-Remediation-Servers VSA is present in the Access-Accept message, for each IP address present in the VSA a 'permit all traffic to/from this IP address' ACL will be applied on the quarantine VLAN. This will allow traffic to/from the remediation servers to pass unhindered in the Quarantine VLAN while all other traffic will be dropped.