NTP VRRP Virtual IP support

This feature allows switches to configure the VRRP (Virtual Router Redundancy Protocol) virtual IP as an NTP server address. The NTP server, when configured on the VRRP master, listens on the actual IP and virtual IP address for NTP clients.

On the VRRP backup node, only one socket is opened and bound to the physical IP address alone. Once a node transitions to the VRRP master, the ExtremeXOS software re-triggers a listen on the interface to ntpd for it to open a socket and bind to the VRRP VIP.

A flag configuration is added for the IPv4 cases, and these are propagated to VLAN (Virtual LAN) Manager clients. NTP uses this to trigger a listen on the interface. For the master node to process non-ping packets destined to the VIP, the software already has a configuration command in VRRP (accept-mode on/off).

Note

If you want to configure VRRP VIP as the server address on NTP clients, enable accept mode.

Limitations

The following limitations exist for NTP VRRP Virtual IP support:

Summit switches configured as NTP clients need to have the bootrom version: 2.0.1.7
We do not recommend FHRP Virtual IPs for NTP configuration because they can cause undesirable behavior when the NTP servers are not in sync, or if the delay is asymmetric. Ensure that both servers derive their clock information from the same source.
This problem can be more acute if a node connected to VRRP peers using MLAG (Multi-switch Link Aggregation Group) and VRRP is in active-active mode. In this case, it is possible that every other packet could be sent to a different switch due to LAG (Link Aggregation Group) hashing at the remote node.

Published March 2020prev | next

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