Very Computer

Hi all

I want to configure a NTP server on a LAN and backup NTP server sited
on other LAN. Remote routers have connectivity with both NTP servers.
I know how i must configure remote routers.

ntp server x.x.x.x prefer (NTP server)
ntp server y.y.y.y (NTP server backup)

But anybody can tell me how I must configure NTP server and backup NTP
server?
Must i change backup ntp server stratum value higher than ntp server
stratum value?

I want:

1.- Remote routers syncronize its clock with NTP server, and if NTP
server is down, Ther syncronize its clock with backup NTP server.

2.- Backup NTP server must syncronize its clock with NTP server clock,
but if NTP server is down, when it go up, NTP server must syncronize
its clock with Backup NTP server. I think that if I configure backup
NTP server with ntp server x.x.x.x (x.x.x.x is IP of NTP server), if
NTP server go down, backup NTP server will be unsyncronized and remote
routers doesnt syncronize with backup NTP server.

Anybody can help me?

Cisco has a good white paper on NTP at
http://www.cisco.com/warp/public/126/ntpm.html

Quote:> Hi all

> I want to configure a NTP server on a LAN and backup NTP server sited
> on other LAN. Remote routers have connectivity with both NTP servers.
> I know how i must configure remote routers.

> ntp server x.x.x.x prefer (NTP server)
> ntp server y.y.y.y (NTP server backup)

> But anybody can tell me how I must configure NTP server and backup NTP
> server?
> Must i change backup ntp server stratum value higher than ntp server
> stratum value?

> I want:

> 1.- Remote routers syncronize its clock with NTP server, and if NTP
> server is down, Ther syncronize its clock with backup NTP server.

> 2.- Backup NTP server must syncronize its clock with NTP server clock,
> but if NTP server is down, when it go up, NTP server must syncronize
> its clock with Backup NTP server. I think that if I configure backup
> NTP server with ntp server x.x.x.x (x.x.x.x is IP of NTP server), if
> NTP server go down, backup NTP server will be unsyncronized and remote
> routers doesnt syncronize with backup NTP server.

> Anybody can help me?

Jmfrah

Where are your NTP servers getting their time from? If their time
sources are two separate authoritative sources then you should let the
NTP process on the routers figure out which to trust the most, rather
than skew the stratum to influence their decision.

If the servers are just using their internal clocks then that's a
different matter, they're likely to drift apart and confuse the
routers.

NTP doesn't really rely on 'fail-over' type resilience. It uses
multiple sources of time to qualify the information it receives and
deduce the most likely 'intercept' of the possible values. Ideally you
want three servers though you could possibly do some 'peering' between
routers to help their calculations.

Regards

Andy