Clearing DNS cache and DHCP lease table
Posted: Fri Aug 28, 2015 9:36 am
Good news - my new 8800AXL stays up permanently replacing the 7800N which had started rebooting several times a day.
Also good news - many of the config changes which required the 7800N to be restarted can be done without a restart of the 8800AXL.
Now the problem:
I have assigned fixed IP addresses to most (but not all) of the devices on my network.
To refer to them by name, I've created entries in the Static DNS table.
I created an isolated wi-fi SSID which uses the subnet 192.168.2.xxx; the rest of my network is on 192.168.1.xxx
As a test, I connected my iMac to the guest network, and it acquired the address 192.168.2.8
I suppose I should have explicitly release the DHCP lease, but I didn't.
I just reconnected the device to its normal static 192.168.1.5 address
The problem is that the DNS nameserver continued to resolve imac.local.host to 192.168.2.8
Even when I added an entry to the static dns table pointing imac.local.host to 192.168.1.5, it didn't change the DNS server's response of 192.168.2.8
After 24 hours when the DHCP lease for 192.168.2.8 had expired, the DNS didn't change.
Since there is no command to do so, eventually I had to reboot the 8800AXL to flush the DNS cache.
Unfortunately it also cleared the DHCP table.
Some devices still thought they had a long lease on their address, and the DHCP server (having cleared the DHCP table) was handing out the same addresses to other machines.
What I really needed was a command to flush the DNS cache without clearing the DHCP table.
An interface to delete individual DHCP leases would be useful (like on my old Thomson Alcatel Speedtouch 716WL)
Also good news - many of the config changes which required the 7800N to be restarted can be done without a restart of the 8800AXL.
Now the problem:
I have assigned fixed IP addresses to most (but not all) of the devices on my network.
To refer to them by name, I've created entries in the Static DNS table.
I created an isolated wi-fi SSID which uses the subnet 192.168.2.xxx; the rest of my network is on 192.168.1.xxx
As a test, I connected my iMac to the guest network, and it acquired the address 192.168.2.8
I suppose I should have explicitly release the DHCP lease, but I didn't.
I just reconnected the device to its normal static 192.168.1.5 address
The problem is that the DNS nameserver continued to resolve imac.local.host to 192.168.2.8
Even when I added an entry to the static dns table pointing imac.local.host to 192.168.1.5, it didn't change the DNS server's response of 192.168.2.8
After 24 hours when the DHCP lease for 192.168.2.8 had expired, the DNS didn't change.
Since there is no command to do so, eventually I had to reboot the 8800AXL to flush the DNS cache.
Unfortunately it also cleared the DHCP table.
Some devices still thought they had a long lease on their address, and the DHCP server (having cleared the DHCP table) was handing out the same addresses to other machines.
What I really needed was a command to flush the DNS cache without clearing the DHCP table.
An interface to delete individual DHCP leases would be useful (like on my old Thomson Alcatel Speedtouch 716WL)