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Questions tagged [ntp]

For questions about the Network Time Protocol (NTP) on network devices, where this tag should only be used when configuring NTP on an on topic network device.

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What is the use of NTP server when devices have accurate time?

Just as the questions says, why there would be an NTP server when the devices already got the internal clock and are accurate.
Jugert Mucoimaj's user avatar
0 votes
0 answers
57 views

Time synchronization at network Level

Let suppose we have a scenario where we are getting 5G network and its phase and time synchronization for the radio interface is PTP(precision time protocol). Using that 5G network I have my local ...
Nifty's user avatar
  • 13
0 votes
0 answers
38 views

Cisco Kron Job starts later and later

I use a Kron job to ring a shit bell for our manufacturing plant. The application works, but the job starts 35+ seconds late. The problem seems to be getting worse, a few days ago it was at 35 secs ...
noobInTraining's user avatar
0 votes
1 answer
131 views

How does NTP synchronisation work?

I am trying to get a basic understanding of the NTP Algorithm. I read the Time Exchange section here. I have a few questions regarding it. Server A and Server B are trying to synchronise their times. ...
Ashwin's user avatar
  • 133
0 votes
1 answer
1k views

Aruba 2930M - the NTP server is unreachable

My Aruba 2930M switch cant reach the NTP servers. Below is the following conf: ##################### OOBM IP Address 192.168.90.34 IP Version IPV4 IP Mode Manual Subnet Mask 255.255.255.0 ...
Kikomi's user avatar
  • 27
0 votes
1 answer
85 views

Juniper MX: NTP broadcast on two VRFs with the same addressing

In Juniper, NTP broadcast is set at system level, so two VRFs cannot use the same addressing and use NTP broadcast at the same time. Is there any alternative?
Luis Andrés García's user avatar
4 votes
1 answer
2k views

Cisco IOS NTP do not sync time after reboot

I try to setup automatic syncing time on Cisco Catalyst 2960-CG-8TC-L switch using following command. ntp server 0.cz.pool.ntp.org and it works and sync time but after switch reload it does not sync ...
Misaz's user avatar
  • 143
0 votes
1 answer
651 views

NTP Sync issues between Palo Alto 3260 and Juniper MX10003

I'm using a Microsemi S650 as the primary ntp server and a Juniper MX10003 as the secondary ntp server. I have the palo alto 3260 configured as follows: [edit deviceconfig system ntp-servers] ...
Ben's user avatar
  • 157
1 vote
2 answers
90 views

Why is accurate time important with networking? [closed]

Seems like a broad and vague question and it is but hopefully the below examples can give a better idea of what I'm really questioning. Recently ran into an issue where because of my system time was ...
Tagger5926's user avatar
3 votes
1 answer
429 views

Query on PTP Transparent Clock

I had a query in PTP Transparent Clock(TC), Please consider the below picture for my question. I will try to express my question with the help of a real world example Say, two places Place_A <----...
user avatar
0 votes
1 answer
775 views

How important is it for time to be synchronized between adjacent OSPF neighbors?

I have two routers that; when first powered up, will initially form full OSPF neighborship with each other and exchange their respective advertised routes with each other. After approximately 2 hours ...
dutsnekcirf's user avatar
2 votes
2 answers
1k views

Clock Synchronization in a Network

I had a query in Clock Synchronization in a LAN.. If we already have clock synchronization in a network with the help of preamble field in an Ethernet frame. Why should we need still protocols such ...
user avatar
0 votes
1 answer
85 views

MD5 Authentication Character Length

I have a Cisco SG350-10P. I am trying to connect it to my SNTP server. It requires an MD5 authentication key is required to connect and it is a 16 character password. But my switch will only take 8 ...
JukEboX's user avatar
  • 461
1 vote
1 answer
123 views

Cisco swtich stacked NTP configure

I have two cisco switches (WS-C3850-12XS-E) stacked by stack cable. I want to configure ntp on them. How to configure ntp on those about time synchronization?
user889527's user avatar
4 votes
1 answer
2k views

Will the packet be dropped when the number of hops equals to default TTL?

From my understanding, the default TTL represents the maximum number of hops allowed such that the packet may reach the host. NTP Documentation Archive: ttl - This option is used only with ...
M. Xu's user avatar
  • 43
5 votes
1 answer
3k views

What is the effect of using "ntp allow mode control 0"?

I am attempting to mitigate the issues surrounding bug report CSCum44673. According to the software release notes found here, I need to ensure that all of my routers are on IOS version 15.2(2) or ...
dutsnekcirf's user avatar
5 votes
1 answer
380 views

Is it bad practice to use a Virtual Router for NTP-Clustering?

I'm trying to find information on whether it is possible to enable an NTP cluster containing multiple routers, that are configured with VRRP to share the same address. I am aware that with many ...
cyacedev's user avatar
3 votes
1 answer
64 views

Simple NTP question

Setting up NTP on a cisco 3560 so clients can be all on the same time. The switch it only used at layer 2. Outside of having a management VLAN for SSH, there isn't currently any config for anything ...
keelsinit's user avatar
1 vote
1 answer
193 views

NTP monitoring issue

I have set up a measurement in our monitoring tool to check the state of the NTP, the target is a Nexus 5596, i'm using the following oid : 1.3.6.1.4.1.9.9.168.1.1.11 But I'm getting : ...
Samirtow's user avatar
2 votes
1 answer
1k views

Cisco ACL for NTP

We have Cisco ACL configured for all inbound traffic and today i have add NTP to allow few remote NTP server to sync tim. I have created object-group NTP group and multiple remote NTP server in that ...
Satish's user avatar
  • 4,379
1 vote
1 answer
410 views

How does Peer-to-Peer NTP resolve time variance?

If I have two servers set up with peer-to-peer NTP and both have different times, how do they decide what time to use?
kojow7's user avatar
  • 157
4 votes
2 answers
1k views

Cisco Switch - Why do I need to do time synchronization for them

I manage a mid-sized Industrial automation network. I have roughly 10 client machines and 4 server machines. Up until now, we didn’t have a GPS clock in the network. One of the machines, server-A, ...
Aarti's user avatar
  • 41
0 votes
3 answers
6k views

Endpoint is getting ARP response but not able to ping it/ connect it [closed]

I have a endpoint which is on vlan x and a SNTP server on vlan Y of same cisco switch. I am trying to synchronize my time from SNTP server. endpoint is able to resolve ARP and get the mac of SNTP ...
Vikash Srivastava's user avatar
1 vote
2 answers
938 views

Cisco IOS NTP server config causes slow boot

I tried to configure my router to use NTP server. I thought it is trivial but I was wrong. It causes a very nasty problem when router have yet to gain internet access (during boot). I see the ...
some user's user avatar
  • 252
2 votes
1 answer
18k views

Cisco NTP Clock is unsynchronized

I have two internap NTP server and i set them up on Cisco Router but this is what i am getting. R1#show ntp associations address ref clock st when poll reach delay offset ...
Satish's user avatar
  • 4,379
2 votes
2 answers
11k views

NTP synchronization issue with Cisco ISE

We have a Cisco ISE 2.0 in our lab doing some 802.1X testing. To have synchonized times, we use an NTP server in the same subnet as the ISE to sync all the components (stratum 3, based on Bluecat ...
Daniel's user avatar
  • 1,071
1 vote
1 answer
337 views

Will a cisco Router relay NTP information to a Checkpoint firewall?

so i have a checkpoint firewall and a cisco router , cisco router clock os synchronized via a public NTP server, as we know, a route which a ntp client can also relay the ntp information, will it ...
user27170's user avatar
4 votes
2 answers
635 views

NTP architecture questions

I have a question about NTP. We want to setup our core switches as NTP master for our network. We have three data centers. Site A : Two Nexus as core Site B : two Nexus as core Site C : two 6800 (in ...
Vinny's user avatar
  • 43
3 votes
1 answer
904 views

IOS does not respond to NTP queries unless client is in "peer" ACL

I have set up NTP on a Cisco IOS device running IOS 15.2M, and this is my bare-bones config used for testing: ip access-list standard IPV4-ACL-NTP-PEER permit <UP.STREAM.NTP.SERVER> log ! ip ...
tlund's user avatar
  • 191
2 votes
3 answers
266 views

How stable are clocks in network equipment [closed]

Most high end network equipment (switches and routers) can act as a NTP-server for hosts in the network, but I cant find any information on how stable these are. Does anyone have any information or ...
Peter's user avatar
  • 406
1 vote
1 answer
2k views

Dell X1052 External NTP

I have a Dell X1052 network switch and I am trying to setup SNTP. I don't have a time server on my network and my SonicWall TZ400 doesn't seem to work as an NTP server. How do I get SNTP working to ...
user1624184's user avatar
2 votes
3 answers
3k views

How to get local time from internet

I am programming for an embedded device and I want it to display the local time. I know I can get the UTC time by NTP or SNTP. However how can I convert it to the local time if I do not want the user ...
eepty's user avatar
  • 121
2 votes
2 answers
335 views

Effects of local switch time on network performance

Given a collection of switches all communicating together, will the local time on the switching equipment configuration have any bearing on performance, or just a common reference point when ...
Sabre's user avatar
  • 123
1 vote
2 answers
2k views

Route NTP traffic through Routing-Instance

Switch 2 needs to route it's NTP requests through a specific vlan that is setup on a routing-instance. Current NTP setup on switch 2 is set system ntp server 10.0.0.21 set system ntp source-...
Nixphoe's user avatar
  • 187
3 votes
1 answer
907 views

NTP Authentication within a vrf

I have a Cisco ASR1002 WAN router with multiple vrfs per department. Each vrf has a loopback interface on the router, which can be used as an NTP server for remote devices in the respective vrf/...
James Mullan's user avatar
2 votes
2 answers
2k views

How are UDP source ports mapped on a NAT?

Here is an example use case; I am curious to see how this is suppose to work and why: Someone has a NAT router from their ISP. Behind the router are 2 PCs running Linux and using ntpd. ntpd sends ...
hooby3dfx's user avatar
  • 121
9 votes
2 answers
3k views

Which QoS classification should be applied to NTP?

Cisco's Enterprise QoS Solution Reference Network Design suggests classifying NTP as network management traffic and marking it as CS2: When addressing the QoS needs of Network Management traffic, ...
Stephen Craven's user avatar
4 votes
1 answer
1k views

Time synchronization on cisco switches

I have LAN that must not be on Internet. I have a lot of switches. How to make core switch 4500 series to be some kind of NTP server, and all other switches to adjust their time with this core? Goal ...
John's user avatar
  • 812
3 votes
2 answers
4k views

Access rule that permits NTP response

Nagios is used from HOST1 to check the NTP server on HOST2. One of the servers resides in an ACL. The assumption was that ip access-list extended vlanX permit udp host HOST1 X Y eq ntp deny ip ...
030's user avatar
  • 553
4 votes
1 answer
5k views

Cisco Nexus 7k as NTP server

Anyone have experience with setting up their Nexus 7k core as an NTP server? I was thinking the code would look like below: ntp master stratum 2 ntp server ns.arc.nasa.gov prefer ntp server bitsy....
BaconManic's user avatar
6 votes
2 answers
3k views

Cisco NTP server does not respond to queries

I have an NTP configured through out our in a hierarchy. 100% reliable with regards to providing time for Cisco devices. At one of our sites we allow cameras, servers, and workstations to utilize our ...
henklu's user avatar
  • 799