I've beating my head against the the above said problem for a quite a while. Our client has a very strict security policy and they require all standard protocol to comply with the expected behaviour. It was discovered that their 3750 switch running c3750-ipservicesk9-mz.122-25.SEE3 software and configured to sync its time with an external public NTP server triggers IPS signature - DNS Info leak. The problem is that the switch initiates the packet on UDP port 53 and not as I would expect on port 123 for NTP. Of course I can tune the IPS sensor and make it not to fire this signature but the client needs to know why it is happening and if it is faulty IOS software that doesn't comply to the rules.
Re: 3750 switch NTP time syncronization triggers IPS
Well, the switch has never had any idea about DNS server as it is not configured with it. And secondly, as far as I understand NTP configuration on the IOS devices is supposed to use IP addresses only. You can't enter the FQDN for NTP server, i.e. nist.gov or something like this.
I have another question on NTP on the switch. It is 3750 switch with a number of L3 interfaces (VLANs) configured:
Why do I see NTP packets originated from VLAN13 interface only, i.e. 192.168.13.254 ?
I don't have any source interfaces for NTP on the switch:
Question We run asr9001 with XR 6.1.3, and we have a very long delay to
login w/ SSH 1 or 2 to the device compare to IOS device. After
investigation, the there is 1s delay between the client KEXDH_INIT and
the server (XR) KEXDH_REPLY. After debug ssh serv...
Introduction The purpose of this document is to demonstrate the Open
Shortest Path First (OSPF) behavior when the V-bit (Virtual-link bit) is
present in a non-backbone area. The V-bit is signaled in Type-1 LSA only
if the router is the endpoint of one or ...
Hi, I am seeing quite a few issues with patch install and wanted to
share my experience and workaround to this. Login to admin via CLI, then
access root with the “shell” command Issue “df –h” and you’ll probably
see the following directory full or nearly ...