07-15-2015 02:44 AM - edited 03-05-2019 01:53 AM
Hi Folks
I'm facing an issue while configuring IP SLA for DNS trigger between two routers connected to each other like R1 <<>> R2 .
R1 - IP 10.1.2.1
R2 - IP 10.1.2.2
Please find below helpful logs .. Looking for your thankful assistance
-----------------------------
R1 Config.
ip sla 1
dns 10.1.2.2 name-server 10.1.2.2 source-port 53
timeout 100
threshold 500
frequency 9
ip sla schedule 1 life forever start-time now
!
R1 show ip sla statistics
R1#sh ip sla statistics
Round Trip Time (RTT) for Index 1
Latest RTT: NoConnection/Busy/Timeout
Latest operation start time: *00:13:56.363 UTC Fri Mar 1 2002
Latest operation return code: Timeout
Number of successes: 0
Number of failures: 36
Operation time to live: Forever
R1 debug ip sla err
*Mar 1 00:11:59.371: IP SLAs(1) dns operation: Error code=4
*Mar 1 00:11:59.371: IP SLAs(1) Scheduler: Updating result
*Mar 1 00:11:59.375: IP SLAs(1) Scheduler: start wakeup timer, delay = 8988
R1#
*Mar 1 00:12:08.363: IP SLAs(1) Scheduler: saaSchedulerEventWakeup
*Mar 1 00:12:08.363: IP SLAs(1) Scheduler: Starting an operation
*Mar 1 00:12:08.367: IP SLAs(1) dns operation: Starting dns operation
*Mar 1 00:12:08.367: IP SLAs(1) dns operation: Query addr - 10.1.2.2
*Mar 1 00:12:08.367: IP SLAs(1) dns operation: actual target queried = 2.2.1.10.in-addr.arpa
R1#
*Mar 1 00:12:17.371: IP SLAs(1) dns operation: Error code=4
*Mar 1 00:12:17.371: IP SLAs(1) Scheduler: Updating result
*Mar 1 00:12:17.375: IP SLAs(1) Scheduler: start wakeup timer, delay = 8988
07-15-2015 04:12 AM
Hello,
You have to configure the other router as a dns server.
But i dont think it will work. Unless you were querying a working dns server.
But based on the debug output the ip sla source is trying to query the dns server as per the output below:
*Mar 1 00:12:08.367: IP SLAs(1) dns operation: actual target queried = 2.2.1.10.in-addr.arpa
Mar 1 00:12:17.371: IP SLAs(1) dns operation: Error code=4
HTH
Please rate helpful post.
Regards,
Steve
07-15-2015 05:31 AM
Hi Steve
It is already R2 as DNS server
07-15-2015 05:39 AM
Hello,
Why are you trying to resolve the "10.1.2.2" string in DNS? This would actually mean that you want a reverse lookup from an IP address back to a fully qualified domain name, that is, a PTR record. You would need to create a PTR record on the DNS for this purpose. Usually, you should be looking for a normal lookup from a domain name to an IP address, such as "www.google.com" or "www.yourdomain.com".
Best regards,
Peter
07-15-2015 08:54 AM
Hi Peter
I just thought that since 10.1.2.2 is R2 interface IP and as long as configured the same as DNS server through CLI . That might make R2 as server for lookup . Could you please elaborate me more how can make this works .
07-15-2015 09:04 AM
Hi Majed,
The SLA probe should be configured similarly to this:
ip sla 1
dns www.google.com name-server 10.1.2.2 source-port 53
timeout 100
threshold 500
frequency 9
ip sla schedule 1 life forever start-time now
Best regards,
Peter
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