topic Re: NTP Vulnerability for Cisco router 28000 in Network Security

NTP Vulnerability for Cisco router 28000

Sriinuvas — Sat, 24 Jun 2023 16:53:14 GMT

Hi Firends,

We wants to apply NTP Vulnerability fix in cisco router, below are the requirement and do the needful.

1. We want to use NTP server as Microsoft (Cloud), means want to do client configuration on Cisco router.

2. no other NTP server should not communicate (May be need some access list, so that my router should reach-out only Microsoft NTP server only, not any other could NTP server.

Please help me for sample configuration.

Thanks in Advance,

Srinivas.

Re: NTP Vulnerability for Cisco router 28000

Flavio Miranda — Sat, 24 Jun 2023 17:20:29 GMT

Basically you need

conf t

clock timezone GMT- (your GMT)
ntp peer <Microsoft NTP> prefer normal-sync

This should be enough. For ACL but if you need to add

access-list xx permit udp host <your router> <Microsoft NTP> eq ntp

Re: NTP Vulnerability for Cisco router 28000

Srinivas N — Sat, 24 Jun 2023 17:32:30 GMT

Thanks for your response and is it should be in wan interface?

If possible, please help me with configuration in global part and interface part.

Re: NTP Vulnerability for Cisco router 28000

Flavio Miranda — Sat, 24 Jun 2023 17:42:50 GMT

On the wan interface you can to

int Gix/x

access-group xx in

Re: NTP Vulnerability for Cisco router 28000

Srinivas N — Sat, 24 Jun 2023 18:05:17 GMT

Thanks Flavio, will try and confirm you.

Re: NTP Vulnerability for Cisco router 28000

Flavio Miranda — Sat, 24 Jun 2023 18:25:49 GMT

Only keep in mind that the ACL may need to be more complex then that in order to handle other trafffics. I am considering only ntp