DHCP/NAT to wired clients not working.

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Level 1

66 points

DHCP/NAT to wired clients not working.

Yesterday my wired clients lost their DHCP assignments from my AirPort Extreme (802.11ac) router and I can't figure out why that happened. This includes recent model iMac, a TiVo Roamio, an HP laser printer and a Drobo 5N. All of them have DHCP reservations by MAC address. All of them are connected with known good cables. All my wireless clients are fetching IPs via DHCP just fine, it's just the wired ones. In addition I have a second AirPort Extreme to extend the network. The wired clients connected to that one are working just fine.

I tried swapping the two AirPort Extreme routers to see if it was a hardware failure, but both exhibited the same problem when I restored my saved settings. I'm just wondering what's causing it now when I've been running the same basic router configuration for years, going back multiple versions of AirPort Extreme router hardware.

If I had to guess, I'd assume there is some kind of DHCPv6 weirdness affecting the physical LAN ports.

Has anybody encountered a similar problem and know a solution?

Airport Extreme 802.11ac, OS X Mavericks (10.9.5)

Posted on Oct 8, 2014 1:00 AM

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Answer 1

Oct 8, 2014 1:17 PM in response to Eugene Chan2

It is extremely odd..

Just the shut down of the network and restart of swapping the two AE should have got things started.

I presume both the AE are AC models??

Reset the main router to factory and do a minimal setup.. leave the dhcp reservations alone.. do the wired clients pick up the IP if there is no reservation?

Do you have IPv6 set to link-local only in the computer? That is always worth doing.. but I don't think it has anything to do with the problem as obviously printers etc should be purely IPv4.

You are not hiding some switch?? Secondary router etc on us??

I also presume your main AE is the only router.. no double NAT.. nothing plugged directly into the modem except the AE??

What modem.. make and model although hardly relevant might also be good to know.

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Answer 2

Eugene Chan2 Author

Level 1

66 points

Oct 8, 2014 7:59 PM in response to LaPastenague

Yeah, both AEBS are the 802.11ac model. When I tried resetting to factory settings, the wired connections did receive IP assignments, but as soon as AirPort Utility detected the router and performed its initial configuration, the wired connections went down again. I've tried manually recreating my config from scratch with and without DHCP reservations, I've tried turning off IPv6 on both client devices and the AEBS as well.

As far as hardware is concerned, I only have a switch connected to the second AEBS and it is functioning normally. The cable modem is a Linksys/Cisco DPC3008. It's strictly a cable modem (no phone, wireless/router) so there's no chance of running double NAT. I am on Comcast as well, so all my capable devices should be assigned v6 addresses too.

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Answer 3

Eugene Chan2 Author

Level 1

66 points

Oct 8, 2014 9:41 PM in response to Eugene Chan2

Additionally, I tried using a Motorola SB6141 cable modem as well...had no effect.

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Answer 4

Oct 8, 2014 11:46 PM in response to Eugene Chan2

When I tried resetting to factory settings, the wired connections did receive IP assignments, but as soon as AirPort Utility detected the router and performed its initial configuration, the wired connections went down again.

Hmmm.. strange and wonderful things happen.

Can you please do a few tests.. it will have to be on the computer.. since the other devices will not allow much access.. Please take a screenshot of the ethernet connection setup in the computer.

This kind of thing.

Link Local according to apple is now essential.

See AirPort base station not seen or "An unexpected error occurred" appears in AirPort Utility 6.3

Go to the DNS tab and make sure you have the correct dns.. you can also try setting a google public dns.. 8.8.8.8 is excellent for testing.

Go to the hardware tab and check the speed. It should be set auto to 1Gbit/s but you can manual slow it down to 100Mbit full duplex.. please give that a try.

Then ping the outside world.. ping the router IP which should be 10.0.1.1 unless you changed it.. btw don't change it. Apple seems to assume it won't be.

There is a utility call natutil you can use from terminal.

See Terminal command to check Apple router status. natutil

I have been trying to get people to A. Know it Exists.. B. Use it for this kind of testing.. It doesn't show much but it maybe will help.

Lastly take it to apple for testing as I have suspicions on the quality of the latest AC airports.. especially the ethernet ports can give trouble.

Another test btw is to stick your switch in between the TC doing NAT and the wired computers.. tell me what that gives you??

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Answer 5

Eugene Chan2 Author

Level 1

66 points

Oct 9, 2014 12:52 AM in response to LaPastenague

Already tried link-local IPv6. Also tried using other DNS and manually changing the link-rate to 100Base-T. None of these worked. I'm 99.99% sure this is not a client device issue and it's either the AEBS going haywire or some weird bug involving the CPE or CMTS and its interaction with the AEBS on the WAN port.

Here's the natutil output with -v -i -s switches.

Getting IGD status...ok

WAN connection details:

Connection type: Ethernet

Link status: Up

Download bps: 1000000000

Upload bps: 1000000000

WAN IP connection details:

Connection type: IP_Routed

Connection status: Connected

IP address: 76.102.xxx.xxx

Uptime: 19745

RSIP Available: false

NAT Enabled: true

LAN DHCP configuration:

Configurable DHCP: true

Forwarding DHCP: false

Low IP: 10.0.1.2

High IP: 10.0.1.200

Netmask: 255.255.255.0

DNS domain: (unknown)

Getting IGD status...ok

WAN connection details:

Connection type: Ethernet

Link status: Down

Download bps: 0

Upload bps: 0

WAN IP connection details:

Connection type: IP_Bridged

Connection status: Disconnected

IP address: 10.0.1.49

Uptime: 266078

RSIP Available: false

NAT Enabled: false

LAN DHCP configuration:

Configurable DHCP: true

Forwarding DHCP: false

Low IP: 10.0.1.2

High IP: 10.0.1.200

Netmask: 255.255.255.0

DNS domain: (unknown)

Since it is happening on both AEBS when I swap their configurations, I do not think it is a hardware failure either.

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Answer 6

Oct 9, 2014 3:00 AM in response to Eugene Chan2

If ping from the computer to the main router fails..

Move the computer to the AE and test again with a 1M patch cord.

If it fails I am not sure what to blame.. but I would then plug the computer directly into the modem.. power down the modem to change MAC .. for the main client (5-15min however long you normally do it).. then see if the computer correctly gets IP as well as gateway and DNS..

Note these values down..

Put the AE back and power cycle the modem again.. note again the public IP, gateway and DNS you get on the AE.

Some strange things can happen at times..

As you say with two AE then it seems most odd.

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Answer 7

Eugene Chan2 Author

Level 1

66 points

Oct 9, 2014 3:40 AM in response to LaPastenague

I more or less tried all of that. When I swapped AEBS, the cable modem assigned a new IP since the MAC changed. When the cable modem is connected directly to the iMac, it gets its own IP as well. The iMac has always been connected to the AEBS via ethernet cable and that's when I first noticed it had no connection to the internet. I had to turn it's WiFi NIC on in the meantime.

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Answer 8

Oct 9, 2014 4:33 AM in response to Eugene Chan2

Sorry you did ping the AEBS and it works or not??

Did you ping the WAN IP and then the DNS and Gateway addresses.. keep ping further and further out so you know where the blockage is.

If you cannot get past the AE LAN port.. then it is faulty.. cable is bad etc.

If you get to the WAN IP but no further there is a conflict. Gateway is incorrect.

The tests are pretty conclusive.

And to add to them see if you can get hold of another brand of router..

But I would make one strange suggestion..

Move the IP of the AEBS which is the router from 10.0.1.1 to 192.168.1.1

You do that via the dhcp settings.

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Answer 9

Loner T

Level 9

59,471 points

Oct 9, 2014 6:28 AM in response to Eugene Chan2

Eugene Chan2 wrote:

WAN IP connection details:

Connection type: IP_Bridged

Connection status: Disconnected

IP address: 10.0.1.49

Uptime: 266078

RSIP Available: false

NAT Enabled: false

LAN DHCP configuration:

Configurable DHCP: true

Forwarding DHCP: false

Low IP: 10.0.1.2

High IP: 10.0.1.200

Netmask: 255.255.255.0

DNS domain: (unknown)

Since it is happening on both AEBS when I swap their configurations, I do not think it is a hardware failure either.

I assume this is the second AEBS. It should be forwarding DHCP only. It should not be acting as a DHCP server.

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Answer 10

Eugene Chan2 Author

Level 1

66 points

Oct 9, 2014 2:48 PM in response to Loner T

That is merely how natutil reports any IGD bridgiing another already acting as a DHCP server. I don't think it's even possible to configure DHCP at all on a device for which you've chosen "extend a wireless network."

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Answer 11

Oct 9, 2014 3:26 PM in response to Eugene Chan2

Eugene Chan2 wrote:

That is merely how natutil reports any IGD bridgiing another already acting as a DHCP server. I don't think it's even possible to configure DHCP at all on a device for which you've chosen "extend a wireless network."

Correct and not all the info from natutil is the truth.. which is rather concerning.

A extend wireless device is merely passing the dhcp requests to the main router. It is bridged as far as the routing side is concerned.

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Answer 12

Eugene Chan2 Author

Level 1

66 points

Oct 18, 2014 10:46 PM in response to LaPastenague

Small update, I tried making a fresh config again and it worked for a little while. Unfortunately after what seems like the designated DHCP lease period, the AEBS is not renewing those leases on the ethernet side. I can't explain it. This is obviously not a hardware issue since it's happened on two different AEBS. It's also not a configuration error because I haven't changed anything. I've tried disabling as many extraneous features like DHCP reservations, file/disk sharing, IPv6, guest networks, etc. as possible to take away random variables.

The only thing I can think of is some kind of bug in the firmware itself. It could be caused by anything...date/time settings, the DHCP client in the AEBS, who knows. I'm going to try to buy a wired router tomorrow and turn off DHCP/NAT on the AEBS completely. That's a bandaid fix, but I can't figure this out.

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Answer 13

Loner T

Level 9

59,471 points

Oct 19, 2014 10:06 AM in response to Eugene Chan2

Can you assign static IPs just to the two AEBSs, leaving the other wired/wireless clients with a DHCP configuration?

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Answer 14

Eugene Chan2 Author

Level 1

66 points

Oct 19, 2014 10:51 PM in response to Loner T

The main AEBS receives a public IP from Comcast via DHCP, there's no getting around that. The second AEBS has always used plain DHCP with a reservation of 10.0.1.254 over wireless. I switch it to manual today, no changes. Clients connected via ethernet to the main AEBS do not retrieve their IPs, reservation or not. Wired clients connected to the second AEBS acting as a bridge have no problem retrieving IPs. It is some sort of problem with the ethernet config on the 'master' AEBS only.

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Answer 15

Eugene Chan2 Author

Level 1

66 points

Oct 24, 2014 10:29 PM in response to Eugene Chan2

Minor update. I ended up buying a Cisco RV130 GbE router to put in front of the AEBS(s). Initially I tried bridge mode, thinking the AEBS would function basically like a switch with a wireless radio, but that didn't work. DHCP-only mode seems to have worked though. The RV130 functions as a DHCP server for the 4 ethernet clients, one of which is an AEBS. Reservations are handled by the RV130 as well. Then the AEBS also acts as a DHCP server for any wireless client and the wired clients connected to my AEBS acting as an extender. Reservations for all those clients are done by the first AEBS.

Everything is working fine now, but I still really want to know why the AEBS's ethernet ports weren't working with its own DHCP/NAT service.

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