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Forum Discussion
RBR20 dhcp renew goes wrong
Hi, I have this issue, that the Orbi stops internet routing during the renew process. For no real reason. I have set up a win10 pc, wireshark to investigate the ISP, and eventthough they run very s...
I use directly the connection from my fiber provider.
and what ont/gateway is it from your provider?
There definitely is "something going on", but it is not clear what. I have an RBR50 with Spectrum cable
.
When I perform the experiment:
- Open the Orbi web interface, Advanced Tab, Connection Status
- Open a Widows command interface
- Type ping dns.google.com -t or ping 1.1.1.1 -t (to rule out DNS problems)
- In the Orbi window click on "Renew"
- Observe the ping command
- Renew again.... and again
I get mixed results. Sometimes nothing amiss. Whatever happens takes less than one second. Sometimes there will be one "Destination net unreachable". But there is never a gap of 3-5 seconds.
RFC 2131 (DHCP) appears to be silent on whether the client can use the network during a DHCP renewal (or at least I cannot find anything)
https://datatracker.ietf.org/doc/html/rfc2131#page-34
I am of two minds on the topic:
- The client has asked for an IP address. Until the IP address is approved, the client has no business just assuming that it will be approved and flooding the network with packets using that IP address.
- The client already got the IP address (maybe several hundred times) and is just asking to extend the lease by renewing before it expires.
- The key is "before it expires". RFC2131 is very clear on page 40 that if the lease actually expires, the device must stop using the network until it receives permission.
My next step would be to repeat the experiment after using the Orbi debug page to record the interaction between Orbi and network.
i.e.
- Open http://orbilogin.net/debug.htm
- Check the option Enable LAN/WAN Packet Capture
- Check Start Capture
- Perform the experiment
- On the debug page click Save Debug Log
- Open the debug-log.zip file on the PC
- Extract wan.pcap
- Use Wireshark to display the capture
- Filter the display on "dhcp"
- Note the time display on the dhcp messages to/from the Orbi
- Now that the Wireshark time of the dhcp messages has been learned, remove the display filter and see if the Orbi sends any network traffic between the time of the initial lease renewal message and the approval.
What appears to be the case (to me) is that Orbi stops using the IP during the DHCP process and (in my case) the DHCP renewal is so quick that it is barely noticable (and happens only every six or 12 hours).
Would be useful to know what the DHCP renewal process looks like on this fiber system. (Does it take 3-5 seconds?)
Did that experiment this morning, collecting the Orbi WAN traffic and examining it with Wireshark.
Captured two DHCP renewals:
- First took 0.131552 seconds
- Second took 0.066902 seconds
After both DHCP renewals, the Orbi immediately did an ARP (who has <IP address>?)
There were so few packets between the DHCP request and response that I am not 100% certain if the Orbi sent any traffic or not. The ping command did return that "Destination network unreachable" on one of the renewals, but not on the other. With ping sending at 1 second intervals, this seems like pure chance.
It would probably be a more interesting experiment to be doing a two-way stream (Zoom, Skype, etc.) during the data collection.
In my case, a 0.1 second interruption is too short to notice.
It might be entertaining to contact the ISP tech support and ask them how long the typical DHCP response it. (My guess is the answer will be, "what the heck are you talking about???")
