Admin Guide
Table Of Contents
- Contents
- Chapter 1: Introduction
- Chapter 2: New in this document
- Chapter 3: Basic administration
- Chapter 4: System startup fundamentals
- Chapter 5: Boot parameter configuration using ACLI
- Chapter 6: Run-time process management using ACLI
- Chapter 7: Chassis operations
- Chassis operations fundamentals
- Chassis operations configuration using ACLI
- Enabling jumbo frames
- Configuring port lock
- Configuring SONMP
- Viewing the topology message status
- Associating a port to a VRF instance
- Configuring an IP address for the management port
- Configuring Ethernet ports with Autonegotiation
- Enabling channelization
- Configuring serial management port dropping
- Controlling slot power
- Enabling or disabling the USB port
- Chassis operations configuration using EDM
- Editing system information
- Editing chassis information
- Configuring system flags
- Configuring channelization
- Configuring basic port parameters
- Viewing the boot configuration
- Configuring boot flags
- Enabling Jumbo frames
- Configuring the date and time
- Associating a port to a VRF instance
- Configuring CP Limit
- Configuring an IP address for the management port
- Editing the management port parameters
- Configuring the management port IPv6 interface parameters
- Configuring management port IPv6 addresses
- Auto reactivating the port of the SLPP shutdown
- Editing serial port parameters
- Enabling port lock
- Locking a port
- Viewing power information
- Viewing power status on VSP 8400
- Viewing fan information
- Viewing topology status information
- Viewing the topology message status
- Configuring a forced message control pattern
- Chapter 8: Hardware status using EDM
- Chapter 9: Domain Name Service
- Chapter 10: Licensing
- Chapter 11: Network Time Protocol
- Chapter 12: Secure Shell
- Secure Shell fundamentals
- Secure Shell configuration using ACLI
- Downloading the software
- Enabling the SSHv2 server
- Changing the SSH server authentication mode
- Setting SSH configuration parameters
- Verifying and displaying SSH configuration information
- Connecting to a remote host using the SSH client
- Generating user key files
- Managing an SSL certificate
- Disabling SFTP without disabling SSH
- Enabling SSH rekey
- Configuring SSH rekey data-limit
- Configuring SSH rekey time-interval
- Displaying SSH rekey information
- Downgrading or upgrading from releases that support different key sizes
- Secure Shell configuration using Enterprise Device Manager
- Chapter 13: System access
- System access fundamentals
- System access configuration using ACLI
- Enabling ACLI access levels
- Changing passwords
- Configuring an access policy
- Specifying a name for an access policy
- Allowing a network access to the switch
- Configuring access policies by MAC address
- System access security enhancements
- Displaying the boot config flags status
- Enabling enhanced secure mode
- Creating accounts for different access levels
- Deleting accounts in enhanced secure mode
- Configuring a password for a specific user
- Returning the system to the factory defaults
- Configuring the password complexity rule
- Configuring the password length rule
- Configuring the change interval rule
- Configuring the reuse rule
- Configuring the maximum number of sessions
- Configuring the maximum age rule
- Configuring the pre- and post-notification rule
- System access configuration using EDM
- Chapter 14: ACLI show command reference
- Access, logon names, and passwords
- Basic switch configuration
- Current switch configuration
- CLI settings
- Ftp-access sessions
- Hardware information
- NTP server statistics
- Power summary
- Power information for power supplies
- System information
- System status (detailed)
- Telnet-access sessions
- Users logged on
- Port egress COS queue statistics
- CPU queue statistics
- Chapter 15: Port numbering and MAC address assignment reference
- Chapter 16: Supported standards, RFCs, and MIBs
- Glossary
Time distribution within a subnet
NTP distributes time through a hierarchy of primary and secondary servers, with each server
adopting a stratum, see
Figure 2: NTP time servers forming a synchronization subnet on page 134.
A stratum defines how many NTP hops away a particular secondary time server is from an
authoritative time source (primary time server) in the synchronization subnet. A stratum 1 time
server is located at the top of the hierarchy and is directly attached to an external time source,
typically a wire or radio clock; a stratum 2 time server receives its time through NTP from a stratum
1 time server; a stratum 3 time server receives its time through NTP from a stratum 2 time server,
and so forth.
Each NTP client in the synchronization subnet chooses as its time source the server with the lowest
stratum number with which it is configured to communicate through NTP. This strategy effectively
builds a self-organizing tree of NTP speakers. The number of strata is limited to 15 to avoid long
synchronization loops.
NTP avoids synchronizing to a remote time server with inaccurate time. NTP never synchronizes to
a remote time server that is not itself synchronized. NTP compares the times reported by several
remote time servers.
Synchronization
Unlike other time synchronization protocols, NTP does not attempt to synchronize the internal clocks
of the remote time servers to each other. Rather, NTP synchronizes the clocks to universal standard
time, using the best available time source and transmission paths to that time source.
Use the show ntp statistics command to verify the NTP synchronization status. For more
information, see NTP server statistics on page 225. NTP uses the following criteria to determine the
best available time server:
• The time server with the lowest stratum.
• The time server closest in proximity to the primary time server (reduces network delays).
• The time server that offers the highest claimed precision.
NTP accesses several (at least three) servers at the lower stratum level because it can apply an
agreement algorithm to detect a problem on the time source.
NTP modes of operation
NTP uses unicast client mode to enable time servers and NTP clients to communicate in the
synchronization subnet. The switch supports only unicast client mode.
After you configure a set of remote time servers (peers), NTP creates a list that includes each time
server IP address. The NTP client uses this list to determine the remote time servers to query for
time information.
NTP fundamentals
January 2017 Administering Avaya VSP 7200 Series and 8000 Series 135
Comments on this document? infodev@avaya.com