tacacs-server dns-alias-lookup

[cclem]

All IOS commands entered in the switch take 18 seconds to process.  I noticed that the following command tacacs-server dns-alias-lookup was enabled.  Disabling this command allows the switch to process the IOS commands without any delay.

I can't find any detailed information regarding this use of this command. Can someone provide a real world business use as to when is it appropriate to enable this command?

[Jatin Katyal]

We use this command to enable IP Domain Name System (DNS) alias lookup for TACACS+ servers. Due to this it does reverse dns lookup. In scnarios where we don't have a dns server configured or defined, command cause a dns request to be generated  and it uses broadcast domain (255.255.255.255) and eventually timed out and adds lots of delay.

There are few tacacs+ related known issue with this command. Here is one of those.

CSCtc94806    tacacs-server dns-alias-lookup causes high CPU on TPLUS process

Jatin Katyal
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[minkumar]

Hey

  its a  bug in IOS 15.1, in case if you are using IOS 15.1

Regards

Minakshi (Do rate the helpful posts)