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sempergoofy
Premium Member
join:2001-07-06
Smyrna, GA

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sempergoofy

Premium Member

Any way to make RG forget an inactive DHCP client?

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I was installing a new release of Linux on a server that has three Ethernet NICs in it (one on the motherboard, and a dual-port PCI NIC). Normally I run this system with all three NICs in a bond for failover support within my LAN.

After setting the host name on Linux (which is fsiatlx235), but before I could get things configured correctly, the server had requested as a DHCP client TCP/IP addresses using two of the different MAC addresses within the server from the AT&T RG.

Now things are configured correctly. More than 24 hours (the lease time for DHCP clients from the RG) has elapsed. Yet, when other machines on my LAN perform an nslookup for the machine in question, the RG (as the DNS server) responds with both the inactive address that was formerly passed out to one of the MAC addresses as a DHCP client, as well as the currently leased address that is active on the bond. (Yes, my RG is at 192.168.249.1 and my LAN is 192.168.249.x, not the defaults used by the RG).

 nslookup fsiatlx235
Server:         192.168.249.1
Address:        192.168.249.1#53
 
Name:   fsiatlx235
Address: 192.168.249.145
Name:   fsiatlx235
Address: 192.168.249.151
 
ping -c1  192.168.249.145
PING 192.168.249.145 (192.168.249.145) 56(84) bytes of data.
From 192.168.249.131 icmp_seq=1 Destination Host Unreachable
 
--- 192.168.249.145 ping statistics ---
1 packets transmitted, 0 received, +1 errors, 100% packet loss, time 0ms
 
ping -c1 192.168.249.151
PING 192.168.249.151 (192.168.249.151) 56(84) bytes of data.
64 bytes from 192.168.249.151: icmp_seq=1 ttl=64 time=1.11 ms
 
--- 192.168.249.151 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 1.111/1.111/1.111/0.000 ms
 
 

How does one make the RG quit answering nslookups with the inactive address in addition to the active address? The screenshot above is from the home screen of the RG. The fsiatlx235 system has only wired interfaces through a switch back to the RG.

Edit to add:
Model 3801HGV
Hardware Version 000778-004
Software Version 6.11.1.29-enh.tm

rolande
Certifiable
MVM,
join:2002-05-24
Dallas, TX

rolande

MVM,

Reboot would be the easiest solution. I would think that the name mapping would be tied to the Lease Expiry interval.

Darknessfall
Premium Member
join:2012-08-17
Motorola MG8725
Asus RT-N66

Darknessfall

Premium Member

said by rolande:

Reboot would be the easiest solution. I would think that the name mapping would be tied to the Lease Expiry interval.

Devices pretty much stay on the list forever.

There's the "Clear Device List" button under Diagnostics -> resets, but that requires you to go back in and configure anything all over again if you gave anything statics.

If a device reconnects a year later it'll be leased the same IP address again.

sempergoofy
Premium Member
join:2001-07-06
Smyrna, GA

sempergoofy to rolande

Premium Member

to rolande
said by rolande:

Reboot would be the easiest solution. I would think that the name mapping would be tied to the Lease Expiry interval.

I would have thought it was tied to the lease time, too. And it also makes no sense to me that it is providing the address of an inactive address in addition to an active address for a name lookup.

I reckon I'll just have to reboot the RG. Luckily, the family is not home yet so I shouldn't hear any complaints (I hope).
sempergoofy

1 recommendation

sempergoofy to Darknessfall

Premium Member

to Darknessfall
said by Darknessfall:

There's the "Clear Device List" button under Diagnostics -> resets, but that requires you to go back in and configure anything all over again if you gave anything statics.

Well, this is truly interesting.

I tried a Reboot first. I know that it did the reboot because the phones (I have two Uverse Voice lines) both lost dial tone while it was rebooting. The reboot had no affect on the client list and the duplicate entry with one active and one inactive remained.

It took the Clear Device List to clear everything out. Of course, then an nslookup for fsiatlx235 got me NXDOMAIN. All names appear as "unknown<.mac-address>." after this clear. Performing an ifup then ifdown on the bond device of the server that started all of this caused it to once again lease the address from the DHCP server on the RG, and now nslookup gives the expected response of a single TCP/IP address. The clients in the client list should show up with their hostnames over time in the list after they renew their leases in the next 24 hours I suppose.

NetFixer
From My Cold Dead Hands
Premium Member
join:2004-06-24
The Boro
Netgear CM500
Pace 5268AC
TRENDnet TEW-829DRU

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NetFixer

Premium Member

Your RG is much more cooperative than the NVG510 that I maintain that is used as a semi-public hotspot. I used to use a Motorola 3347 for that task when the circuit was a traditional ATM based DSL service, and I only allowed a max 32 DHCP clients with a 1 hour lease time (which I would sometimes increase to 48 during hot weather to compensate for more people using the swimming pool). With the NVG510 I tried that and found that I needed to increase the max clients to at least 128 or the public hotspot simply stopped accepting new connections (even though there were only a few active WiFi clients connected).

The reason was this:

Allocation types include static and dhcp. Devices that are powered off will continue to appear in the table, but be shown as "off" for a period of more than a day.

I found that "more than a day" was a gross understatement, and neither rebooting the router or doing a "Clear Device List" made any difference.

Here is a current device list, to illustrate the problem that design flaw caused (all of those "off" devices still have that IP address reserved -- and it can't be used by another device until the RG finally decides to release it):




Yes, I know that there are better ways to run a semi-public hotspot, but the client did not want to spend the money.

nwrickert
Mod
join:2004-09-04
Geneva, IL

nwrickert to sempergoofy

Mod

to sempergoofy
said by sempergoofy:

How does one make the RG quit answering nslookups with the inactive address in addition to the active address?

I don't know the answer.

I'm guessing that if you assigned that IP to another device (via the RG settings), that might clear the old owner of the IP. However this is bound to have other side effects.
Moffetts
join:2005-05-09
San Mateo, CA

Moffetts to sempergoofy

Member

to sempergoofy
Every 2wire device I've ever used has been like this, going back at least to the homeportal 1000 series. The interface is six kinds of dreadful, but at least it's consistent.

It's like these devices were designed by jonny ive's evil twin; it looks simple to operate, but even the simplest task will drive you mad.

kode54
join:2003-09-19
Riverside, CA
Sercomm ES2251
(Software) OPNsense
Ubiquiti UniFi UAP-AC-PRO

kode54

Member

He could have opted for the dead easy, but not exactly future proof solution of an Apple AirPort Extreme based device. Those have a guest network feature that isolates each client from the others, and presumably also blocks accessing the administration features as well.

But if you want to do something simple like monitor the device's total ingress and egress bandwidth, or change the WAN MTU, you're SOL. SNMP was eliminated when they introduced the 802.11ac models, and official word is that they're not going to change that, either.