Page Comparison

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_sip._udp.example.com 86400 IN SRV 10 100 5060 examplecorp.dyndns.net
_sip._tcp.example.com 86400 IN SRV 10 100 5060 examplecorp.dyndns.net

Notes on DNS & SRV Records with Polycom Phones

A flaw in Polycom's SRV record use has been identified. Polycom phones don't honor the DNS SRV weight, but they do honor the priority. What this means is that they don't resort the list of records when they get it from DNS. Most DNS servers by default produce the SRV records in cyclical order. This means that for a 3 server cluster there are only 3 combinations that the records will show up in.

A suggested work-around for this problem is to use the bind (9.6 & later) command rrset-order.

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Documentation for rrset-order here: http://www.zytrax.com/books/dns/ch7/queries.html

Wiki Markup

rrset-order

rrset-order

{

order_spec

;

[

order_spec

;

...

]

rrset-order

defines

the

order

in

which

multiple

records

of

the

same

type

are

returned.

This

works

for

any

record

type

in

which

the

records

are

similar

not

just

A

or

AAAA

RRs

and

covers

results

in

the

ANSWER

SECTION

and

the

ADDITIONAL

SECTION.

The

default

is

cyclic

(round-robin).

The

full

specification

of

rrset-order

is

shown

below.

An

'order_spec'

is

defined

as:

class

class_name

][

type

type_name

][

name

"domain_name"]

order

ordering;

Where

'class_name'

is

the

record

class,

for

example,

IN

(default

is

'any'),

type

is

the

Resource

Record

type

(if

none

specified

defaults

to

'any'),

domain_name

limits

the

statement

to

a

specific

domain

suffix

and

defaults

to

root

(all

domains),

order

is

a

key

word

and

ordering

may

take

one

of

the

following

values:

fixed

-

records

are

returned

in

the

order

they

are

defined

in

the

zone

file

random

-

records

are

returned

in

a

random

order

cyclic

-

records

are

returned

in

a

round-robin

fashion

Note:

For

reasons

best

known

to

the

ISC

(BIND's

author)

the

fixed

value

is

now

(BIND

9.6+)

only

available

if

the

configure

option

--with-fixed-rrset

is

used

in

the

build.

Neither

BSD

nor

Debian

standard

packages

use

this

option.

This

is

likely

to

be

true

for

Fedora

and

other

RPMs

but

has

not

been

verified

(use

named

-V

to

check).

For

practical

purposes

only

cyclic

and

random

are

the

available

choices.

Examples

Defines

that

all

equal

records

for

all

domains

will

be

returned

in

random

order.

Code Block
rrset-order {order random;};

Defines

that

all

equal

MX

records

for

example.com

will

be

returned

in

random

order

all

others

in

cyclic

order.

Code Block
rrset-order {type MX name "example.com" order random; order cyclic};

This

statement

may

be

used

in

a

view

or

a

global

options

clause.

Advanced DNS configuration

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