Category: Initial setup | Updated: 7/31/2010 4:28:48 PM | Read: 2654 (Last: 9/5/2010 12:00:14 AM) You might want to provide a second, or third, DNS server to network clients for redundancy or fault-tolerance. All DNS server's provided to clients should be DNS Redirector servers.
Cause
Client computers may skip or switch to an alternate DNS server, even when the primary is available and ready.
Resolution
When implemented for filtering (BlockedIP= setting, as in most corporate environments) all DNS servers provided to clients should be DNS Redirector servers, running on physically different hardware. If a client starts to use an alternate non-DNS Redirector server they will have bypassed your filtering configuration. Additional servers running under the 'Redundant Server Instance' license support the same number of clients as your primary DNS Redirector server license.
When implemented for initial redirection (RedirectIP= setting, as in most HotSpot environments) the server running DNS Redirector must be the only DNS server provided to network clients via DHCP. This is necessary so DNS Redirector can track all clients joining/leaving the network. The only exception is; if a load balancer can direct clients requests to the same DNS Redirector server every time, and only switch servers after one is found completely down - In this configuration additional DNS Redirector servers can be run under the 'Redundant Server Instance' license. If care is not taken so the client computer always uses the same DNS Redirector server, it may appear as if the client is stuck at or bypassing authorization.
When implemented with a catch-all * record (such as during a network emergency, closed network, or a network without access to the Internet) multiple DNS Redirector servers running under the 'Redundant Server Instance' license support the same number of clients as your primary DNS Redirector server license. Related articles FAQ 27 Use in a virtual server environment FAQ 24 Unable to specify single DNS server on Linksys hardware
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