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Network Time Protocol (NTP) (Access Control (Control messages – reading…
Network Time Protocol (NTP)
Access Control
Control messages – reading and writing internal NTP variables
Request/Update messages – actual time synchronization
ntp access-group {query-only | serve-only | serve | peer} <acl>
If multiple ACLs are used,requests are scanned in the following order: peer – accept and reply to clock updates and control messages serve – only reply to clock requests and control messages serve-only – reply only to clock requests query-only – reply only to control messages
(config-if)# ntp disable Stop sending and responding to NTP messages on that interface
ntp source <intf> Source of NTP messages
Server
ntp master [<stratum>]
If stratum is omited, 8 is used. Each peer using server adds 1 to stratum
Internal server is created, running on 127.127.7.1. This IP must be explicitly allowed by ntp access-group peer <acl>, if ACLs are used.
Client
Client is only going to synchronize its clock to another NTP clock source
ntp server <ip> [<ver>] [key <key>] [source <if>] [prefer]
A client can act as a server, serving another clients (cascading queries)
Queries are sent every 60 seconds.
Authentication
Client authenticates the server ONLY !!!
Client:
ntp server <ip> [key <key>]
ntp authenticate
ntp authentication-key <id> md5 <password> ntp trusted-key <id>
Server:
ntp authentication-key <id> md5 <password>
only this is required to send the key to client. Key ID and password must match the one requested by the client (client sends key ID with a request)
Broadcast
Server:
(config-if)#
ntp broadcast
Client:
(config-if)#
ntp broadcast client
Symetric
active mode
Create a peer association if this router is willing to synchronize to another device or allow another device to synchronize to itself
ntp peer <ip> [<ver>] [key <key>] [source <if>] [prefer]
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