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Forum Discussion
DHCP leases not persistant after restart
I work with IP set top boxes, home networks, etc. Recently I upgraded a MoCA based network that had individual access points to Orbi hoping to take advantage of a mesh network. Unfortunately I've r...
NetworkEng wrote:
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Another concerning issue is that the Satellite keeps sending out ARP requests from 192.168.1.250. This must be some preconfigured IP address which doesn't even match the configured network of 192.168.0.0/24. .........
This IP address must be coming from another router in your network. Are you sure that the ISP modem (the internet box) is bridged and is not acting as another DHCP server in the network?
There are no other routers in the network. The cable modem is a Netgear CM1100. The IP 192.168.1.250 has the same MAC address as the other IP 192.168.0.27 that the Orbi Satellite is using. It's just bad behavior, some static backup IP configured on the satellite. It just sits there arping for all the IPs it used to know about before the restart of the Orbi router. All the network clients ignore it since it's on the wrong network. It just suggests to me the router/satellite combo doesn't fully reconfigure itself to the new network range.
I'm actually more concerned about the lack of DHCP lease persistance. Every time I restart the router everything gets a new address (and yes it's the Orbi doing the DHCP). Ironically I noticed it while reserving static IP addresses to avoid things like printers changing IP addresses. I recall folks were having a problem with a particular doorbell and the solution was to give it a static IP. DHCP servers need to remember the addresses they have already assigned when they restart or else there is chaos.
NetworkEng wrote:
....... Ironically I noticed it while reserving static IP addresses to avoid things like printers changing IP addresses. .......
How do you do "reserve static IP addresses"?
NetworkEng wrote:
........ The IP 192.168.1.250 has the same MAC address as the other IP 192.168.0.27 that the Orbi Satellite is using. .......
I think I saw this IP address assigned at first to my satellite. It seems it's a default "temporary" IP address for the satellite when it has no connection to the router. Once the satellite finds the router it will get assigned the correct IP address by the router.
I agree it's likely a temporary IP so the the Orbi router can configure the satellite. I was just surprised to see that it was also sending out arp requests because it's on the wrong network once the network gets changed so it's broken in that regard. It doesn't seem to cause any problems, unlike the DHCP issue. I'm a little surprised on that one because most developers leverage linux source and dhcpd is one of the best and certainly maintains a lease file for use on restart.
FYI, static reservations are under Advanced->Setup->LAN Setup. You can either select an existing DHCP reservation and turn it into a static reservation (client still uses DHCP but always gets the same address) or you can add a new MAC address entry for a device that has a static IP manually configured. The second case prevents a duplicate DHCP assignment of that same address if it's within DHCP scope range. A good DHCP server should always check to see if addresses are in use before assigning them. That doesn't seem to happen either.
NetworkEng wrote:
I was just surprised to see that it was also sending out arp requests because it's on the wrong network once the network gets changed so it's broken in that regard. It doesn't seem to cause any problems, unlike the DHCP issue. I'm a little surprised on that one because most developers leverage linux source and dhcpd is one of the best and certainly maintains a lease file for use on restart.
Sounds like the satellite is having trouble getting its configuration from the router.
Sounds like something in your network configuration might be causing issues.
You mentioned the network was MoCA and had access points. Are you running wired backhaul over MoCA with Orbi? If so, revert to wireless backhaul and see if that resolves your issues.
The satellites do have 192.168.1.250 hardcoded as a backup address. This is used if the satellite is not configured, but I'm not sure whether this is used at every boot-up or only when the satellite has been reset and has no prior configuration.
I'm not sure about the DHCP issues you are having. I run my Orbi in AP mode with another router so I don't see anything like this. What you describe doesn't make sense though. Devices receive addresses via DHCP and will hold onto the addresses until the lease expires. Clients don't know the Orbi rebooted and restarting Orbi doesn't cause your devices to request new addresses.
Something else must be going on. Hard coding IPs into devices could cause problems, if the hard coded addresses were within the DHCP range of Orbi.
st_shaw wrote:
....... Hard coding IPs into devices could cause problems, if the hard coded addresses were within the DHCP range of Orbi.....
NetworkEng If you set static IP addresses in the devices then please make sure these addresses are outside the Orbi's DHCP range, but within the LAN segment (the set netmask in Orbi)
Yes, my DHCP ends at .199 and static assignments are above that.
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What you describe doesn't make sense though. Devices receive addresses via DHCP and will hold onto the addresses until the lease expires. Clients don't know the Orbi rebooted and restarting Orbi doesn't cause your devices to request new addresses.
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Devices do receive addresses from DHCP and typically renew at 50% of lease time. Clients DON'T know the Orbi rebooted and so they keep using their address. Meanwhile the Orbi starts handing out these already in use addresses to new clients. This is the problem I'm trying to get to and hoping somebody from Netgear sees it because it's got to be impacting lots of people. I bet this is one of the reasons many people seem to be loading old firmware. Most devices seem to detect the IP conflict and re-initiate DHCP so the problem resolves fairly quickly but a few devices will hold their address for a long time and so conficts can persist.
Anybody running in Router mode is free to try this. Look at the addresses assigned under attached devices, then do something to restart the router. Go back and see if devices still have the same addresses. I bet not.