NTP behind NAT

[juantovarm]

Hi all,

is it possible to synchronize to an NTP server behind a static NAT? I keep getting this error:

I have been unable to find anything Cisco-related to manycast.

When I eliminate NAT there is no NTP sync error.

I have the following topology

I am working with 3 1841 in my home lab running Cisco IOS Software, 1841 Software (C1841-ADVENTERPRISEK9-M), Version 15.1(4)M8,

Router 2 is my NTP server. R3 has a static NAT configuration from R2 to R3's loopback.

This is R4's NTP config

This is R3's config

Is it possible to run NTP behind NAT? if so, where is my error? How do i enable manycast?

Thanks in advance

[Richard Burts]

I am somewhat confused about what you are doing, especially this part " R3 has a static NAT configuration from R2 to R3's loopback". What is this NAT for? If R2 is the NTP server, and if R4 is successfully establishing NTP sync with R2 then why do you need the translation on R3?

[paul driver]

Hello
As stated by Rick not sure why you are have nat on the loopback - nat is used to “hide” a network so if you wish to hide R2-R3 subnet and source your ntp packets from loopback 0 then change your static nat statement to point to interface serial 0/1/0, do not advertise network 10.0.20.0/24 and source your ntp from loopback 0.

example:
no ip nat inside inside  source static 10.0.23.2 3.3.3.3
ip ntp source interface loopback0

router bgp 300
no network 10.0.23.0 mask 255.255.255.0

interface serial 0/1/0
ip nat outside

ip nat inside inside source static 10.0.23.2 interface serial 0/1/0