Re: [Ddclient-support] DDClient Detecting a Second Gateway (Provider)???

[Larry H. <la...@gr...>]

Ingo:

On Mon, 1 Feb 2010, Ingo Schwarze wrote:

> Hi Larry,
>
> Larry Houston wrote on Sat, Jan 23, 2010 at 09:35:29PM -0500:
>
>> Currently evaluating a "New" Provider, but had left both Gateways left
>> connected to our LAN's Switch.
>
> You mean, you connect your Internet uplink directly to your LAN network
> segment?  This remark is not related to ddclient, but if i understand
> correctly what you are doing, it seems like a firewall is missing from
> that network design.

Instead of Gateways I should have a specified NAT Based Routers, such that 
the Gateways for both Providers were connected to that same LAN 
Segment/Switch.

>> I had assumed that I could just modify Static Gateways on all Computers
>> to switch between "Providers",
>
> That doesn't look like a good approach, it may cause all sorts of issues.
> For example, what about incoming connections?  They will continue to
> arrive via both providers, and you may end up with asymmetric routing,
> just to name one example.  Besides, what about your security policy,
> and how are you planning to enforce it in that kind of setup?

To my knowledge there no asymmetric routing, for those computers using 
Provider #1 the traffic was exiting/returning by Provider 1's Gateway... 
The same for those computers using Provider #2 and Provider #2's 
Gateway...

>> but to my surprise the DDclient (3.7.3 under Ubuntu 8.04) on occasion
>> would use the Gateway of the "Old" Provider and consequently use that
>> for its IP Address Determination and update my DynDNS Entry accordingly!!!
>> Effectively "Flapping" between Providers, switching back to the "New"
>> Provider 5 Minutes after updating the DynDNS Entry to reflect the "Old"
>> Provider's IP Address...
>>
>> Although I have now disconnected the Router for the "Old" Provider from
>> the LAN's Switch and expect the "Flapping" should stop, I am curious to
>> know by what mechanism the DDclient would have been able to "Discover" the
>> Second Router (Provider) without that being specified as a "Static"
>> Gateway???
>
> That's hard to say.
> Ddclient supports are large number of very different algorithms to
> detect the IP address to publish, and you are telling us absolutely
> nothing about your ddclient configuration.

My Dynamic DNS Service is DynDNS and I have DDClient configured for Web 
Detection of my Public IP Address (checkip.dyndns.org)

> If you hope for help, you would need to describe your network
> topology in more detail and to show your ddclient confugration.


                             Internet
                           /          \
                         /              \
                       /                  \
                     /                      \
                   /                          \
                 /                              \
     Provider #1                                  Provider #2
         |                                            |
         |                                            |
         |                                            |
     Cable Modem                                  DSL Modem
         |                                            |
         |                                            |
         |                                            |
     Router #1                                    Router #2
               \                                /
                 \                            /
                   \                        /
                     \                    /
                       \                /
                         \            /
                           \        /
                             Switch
                           /   |    \
                         /     |      \
                       /       |        \
                     /         |          \
                   /           |            \
                 /             |              \
        PC (Cable)      Server (DDClient)      PC (DSL)
        Gateway #1      Gatway #1 ---> #2      Gateway #2

After adjusting the Gateway on the Server where the DDClient was running 
from Gateway #1 to Gateway #2, for short period of time Detect the Public 
IP Address of Provider #1, then switch back 5 Minutes later to picking up 
the "Correct" Public IP Address of Provider #2!!!

--------------------------------------------------------------------------------
# Configuration file for ddclient generated by debconf
#
# /etc/ddclient.conf

pid=/var/run/ddclient.pid
protocol=dyndns2
## To obtain an IP address from Web status page (using the proxy if defined)
use=web, web=checkip.dyndns.org/, web-skip='IP Address' # found after IP Address
server=members.dyndns.org
login=username
password='password'
wildcard=yes
hostname1.dyndns.org
mail=ro...@ho...
--------------------------------------------------------------------------------

Since observing the DDClient momentarily "Flapping" between Providers, I 
now have two separate LAN Segments on two separate Switches until the 
Provider "Evaluation" has been completed...

I was trying to understand what within DDClient or on the Server where the 
DDClient is running would account for the DDClient NOT detecting the 
Public IP Address of Router #2 for whom the Server had been assigned the 
Gateway Address of Router #2???

Any insite would be appreciated, since I have been using DDClient for 
years with a Single Provider/Router/Gateway without any problems???

Larry .....

> Yours,
>  Ingo
>
> --
> Ingo Schwarze <isc...@as...> | Software Engineer | Framework Team
> Astaro AG | www.astaro.com | 76227 Karlsruhe | Germany
>