SpectraLink 8440 - Static DNS Cache

Spectralink 84-Series Series Wireless Telephones Administration Guide
1725-86984-000_P.docx
September 2016 253
Static DNS Cache
Failover redundancy can only be used when the configured IP server hostname resolves
(through SRV or A record) to multiple IP addresses. Unfortunately, the DNS cache cannot
always be configured to take advantage of failover redundancy.
The solution is to statically configure a set of DNS NAPTR SRV and/or A records into the
handset.
When a handset is configured with a DNS server, it will behave as follows by default:
 The handset will make an initial attempt to resolve a hostname that is within the static
DNS cache. For example, a query will be made to the DNS if the handset registers with its
SIP registrar.
 If the initial DNS query returns no results for the hostname or cannot be contacted, then
the values in the static cache are used for their configured time interval.
 After the configured time interval has elapsed, a resolution attempt of the hostname will
again result in a query to the DNS.
 If a DNS query for a hostname that is in the static cache returns a result, the values from
the DNS are used and the statically cached values are ignored.
When a handset is not configured with a DNS server, it will behave as follows:
 When the handset attempts to resolve a hostname within the static DNS cache, it will
always return the results from the static cache.
Support for negative DNS caching as described in RFC 2308 is also provided to allow faster
failover when prior DNS queries have returned no results from the DNS server. For more
information, see RFC 2308.
Summary
Parameter
Used to:
reg.x.server.y.*
Specify the call server used for this registration
dns.cache.A.x.*
Specify the DNS A address, hostname, and cache time interval (ttl)
dns.cache.NAPTR.x.*
Specify the DNS NAPTR parameters, including: name, order, preference,
regexp, replacement, service, and ttl
dns.cache.SRV.x.*
Specify DNS SRV parameters, including: name, port, priority, target, ttl, and
weight
Table 11-11: Configuring the Static DNS Cache
Parameter
Permitted Values
Default
reg.x.server.y.address
dotted-decimal IP address or
hostname
Null
The IP address or host name of a SIP server that accepts registrations. If not Null, all of the parameters in this table
will overrule the parameters specified in voIpProt.server.*. Notes: If this parameter is set, it overrules even if
the DHCP server is available. If this registration is used for Microsoft Office Communications Server 2007 R2 on
Spectralink handsets, this parameter must be in the form OCShostname.OSCdomain_name.