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Problem with CNR 5.5 resolution exception domains

Hi,

Our customer had planned to upgrade from CNR 3.5 to CNR 5.5. We are currently evaluating CNR 5.5 to test out on the resolution exception domains to query external DNS MX records. The following summarizes our findings:

1) The first MX query from client to external DNS will go to the forwarder's DNS, followed by exception DNS. Subsequent query will be from CNR cache. May I know is external query suppose to work this way for CNR?

2) We had selected several sites for MX query testing. A major problem that we faced is that some MX record query were first successful and failed later. Out of 20 queries, 3 sites having DNS request time out. These queries were successful initially. However, they failed when the Max cache TTL expires (our setting is 1000secs). A point to note is that the rest of the 17 sites were still successful. The problem of MX query to these 3 sites can only be resolved if we set all CNR cache settings to zero, including full flush i.e. stop dns service->flush cache->start dns service.

Our baseline for testing include using UNIX DNS bind and we faced no problem with mx query to ALL sites.

Hence, please kindly advise on the above abnormality.

Thanks.

1 REPLY
Silver

Re: Problem with CNR 5.5 resolution exception domains

CNR version 5.5 product release has been diagnosed with a major DNS problem.The problem is slowness, and ultimately the failure, to resolve the non-authoritative name, such as names on the internet.

If the server installation does not utilize resolution exceptions, what you can do is to place the server in slave-mode and configure one or more non-CNR Version 5.5 forwarders.Else,you need to use the earlier version.

Hope this URL will help you

http://www.cisco.com/en/US/products/sw/netmgtsw/ps1982/products_field_notice09186a008009449f.shtml

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