(S)NTP synchronization on SG300 access switches?

Answered Question
Nov 18th, 2011

Hi,

In our network two Domain Controllers are configured as the central (S)NTP Servers. For a switch in Layer 3 mode it is quit easy to synchronise with these (S)NTP Servers. But what is actually the best approach for access switches in layer 2 mode, that are connected to the layer 3 switch? The only IP Address they have are part of the management VLAN ID 1 which is not routable. I am actually looking for something like a broadcast without having to put a NTP Server in management vLAN.

Boudewijn

I have this problem too.
0 votes
Correct Answer by rocater about 4 years 6 months ago

Is your layer 3 switch the gateway for your vlans? Vlan 1 can be routed, the only restriction to this would be if you do not have any routes for vlan1. If your NTP server and layer 2 switch points their default gateway at your layer 3 switch, the layer 3 switch can route traffic across that way.

It really depends how you have the network setup and what device is handling the routing for you on the local network.

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (1 ratings)
rocater Fri, 11/18/2011 - 14:03

Hello Boudewijn,

You should be able to point across vlans using the layer 3 switch as a gateway for your layer 2 switch. Once you have that set you can us your servers to get the time. This setting is under Administration > Management Interface > IPv4 Interface.

Boudewijn Plomp Tue, 11/22/2011 - 10:40

The layer 2 switches are configured with an IP Addres in the management VLAN ID 1, known as the default VLAN. That VLAN is not routable. Correct me if I am wrong.

Sent from Cisco Technical Support iPad App

Correct Answer
rocater Tue, 11/22/2011 - 11:22

Is your layer 3 switch the gateway for your vlans? Vlan 1 can be routed, the only restriction to this would be if you do not have any routes for vlan1. If your NTP server and layer 2 switch points their default gateway at your layer 3 switch, the layer 3 switch can route traffic across that way.

It really depends how you have the network setup and what device is handling the routing for you on the local network.

Boudewijn Plomp Sun, 11/27/2011 - 15:20

Problem solved. I use a default gateway on the layer 2 switches. I was surprised that the default VLAN is routable. I thought i read somewhere it was isolated. Anyway, it works. Thanks.

Sent from Cisco Technical Support iPad App

Actions

This Discussion