mthoward
join:2005-10-12
Andover, MA
| reply to mthoward
Re: [Config] DynDNS.org on Cisco 871
I have convinced myself that DynDNS update does not work properly on a Cisco 871 running Cisco IOS Software, C870 Software (C870-ADVIPSERVICESK9-M), Version 12.4(2)T2, )
After getting my question-mark problem resolved, I saw that the DynDNS updates were happening. If I set the interval maximum to every 2 minutes using interval maximum 0 0 2 0 I observed that it would make the http call to update the entry.
I decided to do further testing to confirm that the updates were happening at the right times.
What I observed is that the DynDNS entry will get updated only after the interval maximum has expired. That is, if the DHCP ip address changes on the interface, it does not update the dyndns entry.
To watch the packets on the wire I plugged into a 10Mbit hub and used a linux system running ethereal to capture all the activity with members.dyndns.org
The unit does not update DynDNS under any of the following events:
* power on the unit
* interface FastEthernet 4 -> shutdown/no shutdown
* release/renew dhcp FastEthernet 4
* unplug the WAN connection
With all these tests I made sure that the DHCP server actually changed the IP address. The changed IP address did not trigger a DynDNS update.
The update did happen after exactly n minutes plus a few seconds ... where n is the number that I plugged into my interval maximum command.
I ran tests at 1 minute, 3 minutes, and 10 minutes.
This leads me to believe that the DynDNS update mechanism is flawed. The recommended interval configuration is interval maximum 28 0 0 0 which causes an update every 28 days. This is because DynDNS will flush you after 28 days. But you cannot make needless frequent updates of a non-changing IP address or their system will cut you off.
So, it seems to me that the DynDNS update implementation is flawed and effectively unusable.
Please tell me if you see flaws in my tests or in my understanding ... or if you have recommendations for other things I should try.
Thanks,
Miguel |
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Zolee
join:2006-01-25
10645
| I noticed the same thing. I used a couple of different routers with the latest images but it sucks.
dyndns.org
1811W works the same way you router does
871 does not work at all, no DDNS updates on the website at all, under any circumstances
2801 same |
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mthoward
join:2005-10-12
Andover, MA
| reply to mthoward
Cisco has given me a prerelease test IOS that fixes this bug with DynDNS update on a Cisco 871.
My testing indicates that it works OK.
They have not told me when it will be 'officially' released.
Although, frankly after months of sending configs & ethereal dumps to Cisco I have lost interest. I had to come up with another solution, so the 871 is sitting unused on my rack ... updating a test DynDNS entry occassionally 
Miguel |
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