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NTP synchronize problem at access layer switch

mukesh chaubey
Level 1
Level 1

Hi

I have cisco router 2600 which is confirgure as ntp master . L3 swtich is connected and one ip confirgured on it which is default gateway of every host in network . cisco L3 switch 3750 is connect to two cisco switch 2960 and that 2960 is connect to approx 24 cisco switch (2960). .all 24 cisco switch is access layer switch its time is not synchronise . only L3 is synchronise with cisco router 2600 .  how to do that. since all switch should has same time.

Screenshot is attached with this mail ..  

10 Replies 10

bamitowpritow
Level 1
Level 1

is the NTP master pingable from the other switches? can you provide us a "show ntp status" of the unsychronized devices?

 

no .its not pingable from switch . but after connecting system and giving ip on system and gateway . system ping to L3 switch .I mean network connection is ok. since there is no ip confirgure on any switch excpet L3 switch .

what to do. ? i need to set the time on every switch .i.e sysnchronise .  when i one the debug ntp command .it also show its unrachable ntp server . how to over come such issue.   

according to your diagram, you could set  ESW1 as NTP server for ESW2 and set all other access switches to use ESW2 as NTP server. It should automatically Synch if ESW2 can reach ESW1.

The problem is not NTP itself but the switches cannot reach the NTP server you are setting. you need to make sure the access switches are able to ping the L3 (ESW1) or ESW2 atleast for NTP to synch.

Actually this is live enviroment . already ntp server is enable on ESW1 and ESW2 is getting synchronise .since ESW2 is reachable to ESW1 .and ESW2 is configure as ntp server <ESW1 ipaddress> and ip address is configure on both ,but rest switch is not reachable to ESW2  .since there is no ip configured on it .all are using as unmagable switch and access layer switch . use to connect the host .and host having gatway of ESW2 .WHICH is reachable . how to sysnchrose time on all switch ?. All switch are using as access layer . no ip configure .how to reach .

 

please revert ..urgently . 

i believe you can only synch NTP via the management IP's, meaning switches should be able to reach each other. if you want to have time configured on your L2 switches, you could probably manually set it per switch.

I dont think that manually setting of time in 24 switch is right way .since there will be some difference in time which i dn't want. is it possible to synchrosie the time with management ip address .if so then how. 

Try ponting ESW1 as the default gateway for the L2 switches. I think the problem is that you are unable to reach ESW1 and not NTP unable to synchronize

how l2 swtich will reach to ESW1 .it will not ping. unless i configure any ip on l2 switch. after configuration of net work ip its reaching to ESW1. in gns3 enviroment same issue is comming .mean if i configure any ip on l2 switch then its pinging .otherwise not. system is ping no issue in network . 

if it is not possible then is there any other way. like by managment ip it will get update time form ESW1. EVERY switch have managment ip . how to do .please revert .thankss in advance.

Hello

on each device assign an management IP make sure each device can reach the ntp server.

Then apply your ntp config and providing you don't have any ACLs for ntp or denying UDP packets and your ntp master is configured to accept ntp broadcasts and queries  they should be able to synchronise.

 

Clock timezone GMT 0 (whatever your timezone is)

ntp server xxxxx

ntp source-address (interface)

 

Res

paul

 

 


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Kind Regards
Paul

Ganesh Hariharan
VIP Alumni
VIP Alumni
Hi

I have cisco router 2600 which is confirgure as ntp master . L3 swtich is connected and one ip confirgured on it which is default gateway of every host in network . cisco L3 switch 3750 is connect to two cisco switch 2960 and that 2960 is connect to approx 24 cisco switch (2960). .all 24 cisco switch is access layer switch its time is not synchronise . only L3 is synchronise with cisco router 2600 .  how to do that. since all switch should has same time.

Screenshot is attached with this mail ..  

Hi Mukesh,

Normal best practices for designing NTP time sync is to sync via Mgmt. network. As with your post i understand all access layer are layer 2 2960 switch which would be having a mgmt. interface for magmt. 

Use the and will be having a default gateway configured towards L3 as well. Make sure L3 Mgmt. ip address is reachable via all access layer and configure ntp sever L3 Mgmt ip in all access layer for time sync.

Hope it Help.

-GI

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