Region : Sweden

Model : TL-R600VPN

Hardware Version : R600VPN v2 00000000

Firmware Version : 1.2.2 Build 140530 Rel.35298n

ISP : ETANET (Norrtalje, Sweden)

Hi,

I have bought the TP-Link TL-600VPN and I have noticed this message,frequently appearing in the log:

DHCPS:Recv INFORM from XX:XX:XX:XX:XX:XX

So I checked what it would mean.

The DHCPInform message explained

Here's the explanation as from the Microsoft:

DHCPInform

DHCPInform is a new DHCP message type, defined in RFC 2131, used by computers on the network to request and obtain information from a DHCP server for use in their local configuration. When this message type is used, the sender is already externally configured for its IP address on the network, which may or may not have been obtained using DHCP. This message type is not currently supported by the DHCP service provided in earlier versions of Windows NT Server and may not be recognized by third-party implementations of DHCP software.

Reference link: http://technet.microsoft.com/en-us/library/cc958940.aspx

It is simply a request for information issued by a DHCP client to the DHCP server.

More details regarding the DHCP protocol can be found at the RFC Editor's homepage as being the current Standards Track (RFC 2131): Dynamic Host Configuration Protocol

Consequences

The DHCP protocol is a logical one, relying on TCP/UDP at ports 67 and 68 and has therefore nothing with the actual hardware to do. Due to the fact that the TP-Link is the originating vendor it is very likely that identical DHCP management code is used in several TP-LINK products. (program code). There are several threads on the TP-LINK Tech Support forum, who mention similar problems, none with a full preliminary diagnostic issue.

I found the following relevant thread describing serious prroblems related to the DHCPInform request and have selected it as an reference:

The "freezing" behavior

This behavior is carefully described in the following thread on the TP-LINK Tech Support Forum: [URL=http://forum.tp-link.com/showthread.php?72467-TL-WR1043ND-gets-frozen-several-times-a-day]TL-WR1043ND gets frozen several times a day[/URL]

I therefore checked whether I can note this "freezing" behavior herein even with the TL-R600VPN in conjunction with the DHCPInform request. I can add that I am regularly watching my TP-Link TL-R600VPN through some of the status windows available from the builtin web server. They are automatically refreshed to show the actual status information.

But sometimes the refreshings ends up with a message indicating that the TL-R600VPN web server not is available (not accessible). I have to manually restart the watching process in my web client, moreover I have some complaints regarding dropped connection from some of my end customers.

Another indication is that it sometimes takes remarkable long time to connect to the builtin web server on the TP-Link TL-R600VPN - I connect via a private 1 GB internal wired connecttion, no heavy load interference.

Similar connection problems are common in an Internet based network environment (client-server or P2P connection as well as state-less connections, for example streaming media) and often hard to diagnose as such things happens momentarily everywhere on the global Internet. But this is within a privare wired LAN completely based on a private address space (ping times generally at 1 ms).

But in my case I suspect the TL-R600VPN as the problematic component due to difficulties to properly handle the standard DHCPInform requests indicated by frequent appearances in the log. The main indication concludes that the "freezing" state, as said by several talkers in the reference thread explanation and I may assume that the program code managing the DHCP is common to several products regardless whether they use WiFi or wired connections. It does not concern the physical layer, rather the logical implementation at application level.

So I would be grateful if the TP-LINK support team can comment these observations and notifications to grant that the TP-LINK DHCP implementation really conforms with the DHCP specification as issued by the IANA through the RFC Editor as the RFC 2131 specification mentioned above.

As a temporary solution I have removed all DHCP based equipment in the LAN using the DHCPInform request to avoid the observed distorsions, detectable in the TL-R600VPN log.

I would also appreciate if others want to commen upon this subject!