Re: Please confirm (conf#374b82a2ebdfc046fcfc1cfa7eff7269)

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>> --- Original Message Follows ---
>>
>> Date: Fri, 9 Dec 2011 10:20:35 -0500
>> Subject: NTP authentication question
>> From: David Johnson <dmjohnson.intl_at_gmail.com>
>> To: ccielab_at_groupstudy.com
>>
>> Hi Experts
>> I'm sure this has been asked before, but I couldn't find it. I am looking
>> at NTP authentication and trying to figure out what the individual
>> commands
>> do.
>>
>> *Here is what I know:*
>> -<ntp trusted-key *id*> only has to be on the authenticating device
>> (usually the client). If it is configured on the server, or a device
>> without a configured <ntp server *ip-addr*> command, it will not affect
>> authentication of any clients. The same goes for <ntp authenticate>
>> command
>> on servers.
>> -Without the key *id* option in <ntp server *ip-addr*>, output from <show
>> ntp association detail> does not say authenticated. That is true
>> regardless of <ntp authenticate> command configured or not. From this, I
>> gather <ntp server *ip-addr* key *id*> is needed for authentication, along
>> with <ntp authenticate>.
>> -<ntp server *ip-addr* key *id*>, the key id must be included in the <ntp
>> trusted-key *id*> command, else the NTP peer will not authenticate. You
>> can have multiple ntp trusted keys as long as they match the server keys
>> and include the key id configured in ntp server command.
>>
>> *Here is what I do not know:*
>> -What does <ntp trusted-key *id*> command provide that <ntp server
>> *ip-addr*key
>> *id*> does not? While it is undoubtedly necessary for NTP authentication,
>> I do not see why the command is necessary in providing information the
>> other command does not.
>> -<ntp authenticate> command is only necessary for the clients, yes? If I
>> wanted the server to authenticate the clients, how would I go about doing
>> that?
>> -If NTP authentication only occurs with <ntp authenticate>, <ntp
>> trusted-key *id*> and <ntp server ip-addr key id>, why does Cisco make the
>> extra commands required? Why not just use the <ntp server *ip-addr* key
>> *id
>> *> command?
>>
>>
>> I have looked this up in books and online, but cannot find the granularity
>> of answers I am looking for. I'm sure there are a host of mistakes in my
>> assumptions, if you could straighten me out, I would appreciate it.
>>
>> *Testing Information:*
>> Below is my configuration, I tried to make it basic, the routers are
>> directly connected, and connectivity is fine:
>> (C2691-ADVENTERPRISEK9_SNA-M), Version 12.4(13b)
>>
>> ---------------------------------------------------------------------------------------
>> *R2 Configuration v1 -- Client (without key command in ntp server ip)*
>> ntp authentication-key 1 md5 021201481F575F 7
>> ntp authenticate
>> ntp trusted-key 1
>> ntp clock-period 17179896
>> ntp server 6.6.6.6
>>
>> (Original message truncated)

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Received on Fri Dec 09 2011 - 13:40:13 ART