RBR20 dhcp renew goes wrong

dapn
Aspirant
Jan 07, 2022
I use directly the connection from my fiber provider.
- plemans
  Guru - Experienced User
  Jan 07, 2022
  and what ont/gateway is it from your provider?
  - CrimpOn
    Guru - Experienced User
    Jan 07, 2022
    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?)

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