Why would 2 Network IP cameras require 2 different DNS addresses for the Primary DNS

Posted on 2010-09-14
Last Modified: 2012-05-10
I have a Panasonic C-131A and D-Link DCS-920 camera.  I talked to there tech support and Panasonic had me set the Primary DNS to my default gateway and the secondary dns to 4.2.2.  D-Link had me set the Primary DNS to and the secondary DNS to  These are both Comcast DNS servers I assume since my provider is Comcast.

After some minor issues and some help from Ken (Experts Exchange) I can now access both the cameras from outside and inside my network !  However I would be curious about:
1.  Why my panasonic c131 uses my default gateway as the primary dns and 4.2.2 as the secondary server.
2.  Why  D-Link requires to use the as my primary and secondary
2.  How do I ping my dyndns (For D-Link I subscribed to DynDNS to obtain a URL for my camera) and do i need to do this from outside my network
Question by:pbo1
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LVL 27

Assisted Solution

Nopius earned 200 total points
ID: 33680447
> 1.  Why my panasonic c131 uses my default gateway as the primary dns and 4.2.2 as the secondary server.

Probably your router is also acting as a DNS cache/DNS server. is a public DNS server that should 'just work' regardless of your provider. Also you may use (google's public DNS server), that is more robust than

> 2.  Why  D-Link requires to use the as my primary and secondary

This is not a requirement, you may use the same or DNS server.

> 2.  How do I ping my dyndns (For D-Link I subscribed to DynDNS to obtain a URL for my camera) and do i need to do this from outside my network

Just run 'ping' or whatever you are using. It's better to ping it from outside. Not all routers support pinging external addresses from internal networks. But this should also work

LVL 20

Accepted Solution

Daniel McAllister earned 300 total points
ID: 33686586
OK... I'm going to throw up my 2-cents worth in here:

1) Why my panasonic c131 uses my default gateway as the primary dns and 4.2.2 as the secondary server?

There are a wide array of DNS servers out there... and typically, "residential gateway routers" act as a "DNS Proxy" (that is, they take the WAN DNS settings that they get from your ISP in the WAN DHCP request and use those servers to resolve DNS queries -- acting as a PROXY for those servers).

However, there are some routers that actually "forward" the DNS settings received from the DHCP response from the ISP to the local systems -- effectively copying the DNS entries received as a WAN DHCP Client into the LAN DHCP Server... but that is less "optimal" because if those settings (WAN DNS) change, the individual hosts won't get the new values until they renew their LAN DHCP addresses.

Now, there are some well-known public DNS servers -- and (as well as and are "popular" GTE (now Verizon) public DNS servers. They are popular because the numbers are so easy to remember! The same can be said for being a public DNS server for Google -- they purchased that IP address strictly for that purpose! There is actually little difference between the two (or all 4)... they are all "robust" and have excellent track records for being well maintained and updated.

So, in essence, picking a primary DNS of your local router is just asking the router to "proxy" your DNS requests to the servers your ISP designates, and setting it to one of the others simply bypasses the "proxy" service offered by your router.

IMHO, on LANs that have no need for internal DNS (like many home networks, but very few work LANs), I choose one of these external DNS servers (I use the series) because the DNS proxy service on some routers isn't very stable. Your ISP may want you to use their DNS server, but it really doesn't matter.

One final thought -- some folks will chatter about the relative "speeds" of the public DNS servers.... if all you're doing is accessing video cameras, this "chatter" will be useless to you... in fact, there is little reason AT ALL for a camera to need access to DNS.... the camera shouldn't be resolving any DNS records at all!

2) Why D-Link requires to use the as my primary and secondary?

Short answer -- it doesn't. Those are your ISP's DNS servers, and as mentioned above, they like for you to use their DNS servers. There is no requirement that you do so, and it shouldn't matter if you do or not.

Think of it like this... remember pay phones? They used to have a copy of the Yellow Pages hanging under them (heck, in the REALLY old days, they had the white pages too!). Now if you removed the phone book from one pay phone and took it with you to another pay phone, it shouldn't matter -- they should have BOTH been the same copy of the phone book, and both should give you the same phone number for the House of Porn you're looking for (joking!)... it's the same with your DNS server... ANY public DNS server (and for that matter, virtually any PRIVATE DNS server) should give you the same values for Internet Domain Name queries.... (the same cannot be said for LOCAL domain queries).

I said it would be short... it doesn't matter which phone book (DNS server) you use... the phone number (IP address of the domain you're looking up) is the same!

3 [or 2 again, if you must]) How do I ping my dyndns (For D-Link I subscribed to DynDNS to obtain a URL for my camera) and do i need to do this from outside my network?

DynDNS is one of many services that allows you to have a world-wide DNS value (IP address) that tries to keep up with your ISP's dynamic allocation of IP addresses. (Some ISPs charge an exorbitant amount for a static IP, others do not.)

Your D-Link router is already programmed to periodically update DynDNS with the right information -- you just tell the router what your domain name and DynDNS account information is, and the router tries to do the rest. (The alternative is to run a client on a system on the LAN that periodically updates DynDNS using a service on that system.)

The whole point of using DynDNS would be so that you can watch your cameras by connecting to (or whatever port you've got being forwarded to one of your cameras).

DynDNS will have use the D-Link router's data (or the client on the system on the LAN) to set the IP address for "" to be your public IP address (say,, and thus your website request gets resolved to your camera's Internet IP and the port number gets the request forwarded to the actual camera.


I hope this helps!!!


Author Comment

ID: 33687359
phenomenol repy !  One point I'm still a little sketchy on.. You indicated that a camera does not need to resolve dns addresses so why does the dlink camera software require me to input prim and secondary dns
LVL 20

Expert Comment

by:Daniel McAllister
ID: 33688207
I would be surprised if it REQUIRED the DNS entries... I would suspect that it asks about them, but that filling them in is optional.

Truth be told, in these days of re-usable code, the prompting for DNS servers is likely just a part of some re-used IP networking configuration routine. There is no harm in telling the camera(s) how to access the Internet, but truth be told, they won't exactly be browsing the net looking to "hook up" with other cameras! :-)

Of course, I don't work for D-Link, so I cannot speak for their products... maybe there is some kind of "check in" or "upgrade" option on the camera that DOES require a full IP configuration -- but I doubt it.

Personally, I'd enter & for the DNS servers in each camera and call it a night!


Author Closing Comment

ID: 33688289
Learned a lot about DNS in 3 replies.  With replies like the above I realize why I subscribe to EE.  Wonderful, well articulated responses such as the above make EE a great learning community.

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