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finding proxy through DNS SRV

jlhbjnhh67
Level 1
Level 1

Can Cisco SPA phones use DNS SRV record to find and select outbound proxy even if there are 3 or 4 answered from the DNS query?

Is there a way to over-ride the cost and weight with custom selection method?

1 Accepted Solution

Accepted Solutions

If implemented according RFC2782 the device should contact proxy1.doman.com, then proxy2.doman.com then either proxy3.doman.com or proxy4.doman.com with probability 50:50.

So what's your question ? Are you asking if particular device's resolver follow the RFC2782 correctly ? You didn't specified device nor exact firmware version so it's not possible to answer.  And implementation may vary between product's model and firmware version.

Just try it on your particular hardware and firmware - it's simple test. It should work if implemented correctly ...

Sorry if it's not the answer you wished for ...

View solution in original post

4 Replies 4

Dan Lukes
VIP Alumni
VIP Alumni
DNS SRV record to find and select outbound proxy even if there are 3 or 4 answered from the DNS query?

I'm sorry, I don't understant the question (especially second half).

Is there a way to over-ride the cost and weight with custom selection method?

No.

Thank you for replying..

DNS SRV query can return more than 2 answers.. possibly 3 or 4..

dig SRV _sip._udp.proxy.doman.com

_sip._udp.proxy.doman.com.    3600 IN    SRV 1 50 5060 proxy1.doman.com. 

_sip._udp.proxy.doman.com.    3600 IN    SRV 2 50 5060 proxy2.doman.com.

_sip._udp.proxy.doman.com.    3600 IN    SRV 3 50 5060 proxy3.doman.com.

_sip._udp.proxy.doman.com.    3600 IN    SRV 3 50 5060 proxy4.doman.com.

In this case, can the phone use 4 proxies according to cost and weight?  3 and 4 would be load balancing where 1 & 2 would provide priority type redundancy..

If implemented according RFC2782 the device should contact proxy1.doman.com, then proxy2.doman.com then either proxy3.doman.com or proxy4.doman.com with probability 50:50.

So what's your question ? Are you asking if particular device's resolver follow the RFC2782 correctly ? You didn't specified device nor exact firmware version so it's not possible to answer.  And implementation may vary between product's model and firmware version.

Just try it on your particular hardware and firmware - it's simple test. It should work if implemented correctly ...

Sorry if it's not the answer you wished for ...

I am currently testing this on Cisco SPA504G 7.4.8a.. I see there are new firmware since I have tested this out. So maybe I will upgrade to the latest and test again. Thank you for your time.