Eric_T
join:2004-03-22
Belgium
| reply to Shootist
Re: "UPDATE" DHCP on Z5 Problem
I can confirm Shootist's test on the Prestige 653-H : the problem only exists in the combination of DHCP renewal + Static address assignment.
As soon as I got rid of the static DHCP for my laptops, the problem went away. I'd still like to see the actual bug fixed, but at least this is an acceptable workaround for most of my customers (so I can finally, after almost a year's wait start upgrading the firmware on all the P653's) |
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Anav
Sarcastic Llama? Naw, Just Acerbic
Premium
join:2001-07-16
Dartmouth, NS
1 edit | reply to Shootist
Excuse me for a bit, I need to go shopping for the usual,,, humble pie and crow! |
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Shootist
Premium
join:2003-02-10
Decatur, GA | reply to Hank
Ha Ha Ha thank you. |
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Hank
Its all relative
Premium
join:2002-05-21
Burlington, WV
1 edit | reply to Shootist
By the authority bestowed upon me by Wolf Blizter, Rush Limbuagh or some obscure government individual, you are now certified as a Clever individual of the highest magnitude.  |
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Shootist
Premium
join:2003-02-10
Decatur, GA | reply to dslpartner
And just what does that mean. I've never been known to be clever!! Rude, a little overbearing and sarcastic Yes, clever No.
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dslpartner
join:2005-02-18 | reply to Shootist
I will post something clever soonish, but I wont be home until monday, so it might take that long :P |
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jig
join:2001-01-05
Hacienda Heights, CA
| reply to Shootist
said by Shootist  :YES we have found a bug. It has NOTHING to do with using the web interface. The web interface was NEVER open when the tests were run. Changes were made and I logged off the Z5 to start the tests. No I was not using one of the test PCs to make changes to the Z5. If the MAC is removed from the static DHCP assignment list the Z5 does update the IP correctly, EVERY TIME. sorry, i didn't mean that you were doing something weird or strange in your tests, i meant that the special case code that i think this bug seems to be related to might have been something to try to deal with the "special case" of someone being logged into the web interface and trying to assign a different static dhcp ip, or something. they coded a special case to cover some situation (the web interface is just a guess, it has to be something about being in the same class c subnet), but they f-ed it up by checking against the wrong address or mask, or checking against it at the wrong time.... something, some rule that they kluged together.
in other words, if i was a zyxel programmer, that's where i'd look. |
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Shootist
Premium
join:2003-02-10
Decatur, GA
| reply to jig
said by jig :i thought static dhcp was supposed to remove the availability of an assigned address whether or not the host with the mac was active or not. and i also thought that it was supposed to assign ips only within the dhcp server range. Yes it removes that IP address from being assigned to any other MAC by the DHCP server. It reserves it for the MAC it is assign TO.
YES and NO. Some router will only allow reserved IPs to be inside the DHCP range some only allow it to be outside the DHCP range, M0n0Wall only allows you to assign reserved IPs outside the DHCP range. I think the Z5 allows both inside and outside the range.
said by jig :your current problems seem exactly like what i would expect to happen if you had assigned static dhcp ips outside your dhcp server range.... some kind of little hiccup. My range is NOT the default, starting at .1.32 and going up, mine starts at .1.100.
said by jig :let me get things straight. when a host with a mac in the static dhcp list tries to acquire an ip address, but has come directly from another subnet within the same class b subnet, then the zywall doesn't respond to the request for an address. I think it responds but it doesn't force the change. In the logs it has entries that say "DHCP assigned x.x.x.x to 00:00:00:00:00:00" but it never really does. This is something for someone that knows more about all this to figure out.
said by jig :further, this process works if the last dhcp assigned address was either outside the same class b subnet, or within the same class c subnet? Class A, B, C,??? YES if the PC has a IP with the first 2 octets different then the Z5 successfully updates the PC to the correct IP. Never tried it with the first octet the same and the last 3 different, I.E. 192.5.x.x.
To be honest I never tried it with a IP in the same subnet with only the last octet different. In any event I could care less whether it did or did not change the IP of the PC in that case because as long as the PC had a IP with all the same octets, and as long as the last octet was unique (not being used be another node), you could connect to it and from it to the rest of the LAN and internet.
said by jig :have you tested if the other router assigns an ip in the same "c" subnet that the z5 works through its issues and gets the static ip thing right when reconnected? No I have not
said by jig :why do NICs remember their last ip, and why/how do they broadcast this when they ask for a new dhcp ip? I think this was answered in another thread, I just don't remember why... Lease time. As it shows in the ethereal files the NIC does broadcast "I have this IP".
What would happen is the NIC would go from x.x.0.x to 0.0.0.0 and then when it got a response from the Z5 it would go back to x.x.0.x instead of the Z5 forcing it to take the x.x.1.x IP. Or at least that is the way I see it.
said by jig :anyway, maybe we've found the bug. it seems like a classic special case bug, but i can't quite get my head around it. it seems like something to do with maybe using the web interface while adjusting static dhcp settings, or maybe with how the static dhcp code keeps other dhcp clients from taking the assigned mac... it's as if they read in the broadcast previously leased ip and then push it into a memory location that gets checked against some rules that don't understand how an ip in the same class b (but not class c) subnet and with a registered mac could be requesting an ip here and now, and then hangs the dhcp handshake. YES we have found a bug.
It has NOTHING to do with using the web interface. The web interface was NEVER open when the tests were run. Changes were made and I logged off the Z5 to start the tests. No I was not using one of the test PCs to make changes to the Z5.
If the MAC is removed from the static DHCP assignment list the Z5 does update the IP correctly, EVERY TIME.
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jig
join:2001-01-05
Hacienda Heights, CA
| reply to Shootist
i thought static dhcp was supposed to remove the availability of an assigned address whether or not the host with the mac was active or not. and i also thought that it was supposed to assign ips only within the dhcp server range.
your current problems seem exactly like what i would expect to happen if you had assigned static dhcp ips outside your dhcp server range.... some kind of little hiccup.
let me get things straight. when a host with a mac in the static dhcp list tries to acquire an ip address, but has come directly from another subnet within the same class b subnet, then the zywall doesn't respond to the request for an address.
further, this process works if the last dhcp assigned address was either outside the same class b subnet, or within the same class c subnet?
have you tested if the other router assigns an ip in the same "c" subnet that the z5 works through its issues and gets the static ip thing right when reconnected?
why do NICs remember their last ip, and why/how do they broadcast this when they ask for a new dhcp ip? I think this was answered in another thread, I just don't remember why...
anyway, maybe we've found the bug. it seems like a classic special case bug, but i can't quite get my head around it. it seems like something to do with maybe using the web interface while adjusting static dhcp settings, or maybe with how the static dhcp code keeps other dhcp clients from taking the assigned mac... it's as if they read in the broadcast previously leased ip and then push it into a memory location that gets checked against some rules that don't understand how an ip in the same class b (but not class c) subnet and with a registered mac could be requesting an ip here and now, and then hangs the dhcp handshake. |
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Shootist
Premium
join:2003-02-10
Decatur, GA
| reply to Brano
You're welcome and thank you for reporting it. I just fired up the C610 I take back and forth to work after I disabled/removed the static DHCP assignment for it and the IP updated right away. So it is definitely tied to the Static DHCP feature. Could be because I am assigning IPs inside the DHCP server range instead of outside it?? But when you check the DHCP table it allows you to check a box TO put that MAC/PC in the static DHCP assignment??
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Brano
I hate Vogons
Premium,MVM
join:2002-06-25
Burlington, ON
 ·TekSavvy Solutions..
1 edit | reply to Shootist
Thanks Shootist I'll send a link to this thread to ZyWall beta folks. Hopefully we'll see fix soon 
EDIT: I've sent it already. |
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Shootist
Premium
join:2003-02-10
Decatur, GA
| reply to OGalati
said by OGalati :Shootist, sorry for the stupid question, but since sometimes you were working with class B IP addresses, are you sure the mask in the Z5 DHCP Server is /24 (255.255.255.0), not /16 (255.255.0.0)? Yeah it's 255.255.255.0. Not sure you could even use the 255.255.0.0 mask with the 192.168.x.x range. I think it is hard coded not to so you can only have 254 clients using that IP range.
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Shootist
Premium
join:2003-02-10
Decatur, GA
| reply to Shootist
Ok here's what I did
I setup 3 PCs, 2 notebooks 1 desktop (one of the notebooks could not run ethereal, it is running 98SE and for some reason was missing a file, so I replaced it with a Dell i8200), both notebooks are running XP Pro, 1 with SP2 (i8200 with 3COM) 1 with SP1 (Second C610 I have with 3COM), desktop is running 98SE.
Setup Static DHCP for all, the 2 notebooks were already setup for this and I setup the desktop for static also.
Used a Linksys BEFSR41 as second router/DHCP server with a IP of 192.168.0.254 and DHCP range starting at .100
Started Ethereal on the C610 while it was connected to the Z5 with a IP of 192.168.1.109.
Disconnected the cable from the Z5 and connected one from the SR. IP changed to the range of the SR with .100 as the last octet.
Reconnected the cable from the Z5 and IP never changed from the one assigned from the SR until I repaired the connection.
Started Ethereal on the i8200 while connected to the Z5 with IP of .1.107 (normal static DHCP assignment). Switched cable to the SR and got a IP in the SR range, .0.xxx. Switched back to the Z5 and again the IP stayed the same as it got from the one it got from the SR until a repair of the connection.
I then turned off the Static DHCP assignment in the Z5 for these 2 notebook and ran the tests again.
Followed the same procedure and this time the Z5 successfully assigned a IP in the range of the Z5. I ran this test twice on each notebook.
So it seems it is NOT necessarily the DHCP server in the Z5 BUT the combo of the DHCP server and using a static DHCP assignment.
Sorry for not including the desktop but the results were the same for it.
Here are the ethereal captures. Sorry for not filtering them I forgot how.
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Brano
I hate Vogons
Premium,MVM
join:2002-06-25
Burlington, ON
·TekSavvy Solutions..
4 edits | reply to OGalati
Shootist seems to be right. If the first two octets are the same the DHCP does not work properly.
I've done this test:
- configured my ZyWall2 as 192.168.1.0/24
- got my laptop on it and obtained an IP address using ipconfig /release /renew
- unplugged the laptop and plugged it to my ZyWall5 configured as 192.168.10.0/24
- the IP didn't get renewed |
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OGalati
join:2005-08-19
Argentina | reply to Shootist
Shootist, sorry for the stupid question, but since sometimes you were working with class B IP addresses, are you sure the mask in the Z5 DHCP Server is /24 (255.255.255.0), not /16 (255.255.0.0)? |
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Brano
I hate Vogons
Premium,MVM
join:2002-06-25
Burlington, ON | reply to Shootist
The first two octets are different.
I'll test it with same octets later tonight. |
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Shootist
Premium
join:2003-02-10
Decatur, GA
1 edit | reply to Brano
Well from MY point of view it isn't. What is your IP range at work and at home?? Are they the same first 2 octets with different 3rd and forth octets. If the first 2 octets are different, 10.x or 172.16 as apposed to 192.168, that doesn't count, I win. Really the problem occurs when the first 2 octets are the same, at least from what I've seen.
I have NO problem getting the correct IP from the Z5 when the notebook has any other IP address then 192.168. If the notebook has a IP of 10.x.x.x the Z5 DHCP updates the notebook to 192.168.1.104. If the notebook has a IP of 172.16.x.x the Z5 update the notebook to 192.168.1.104. If the notebook has a IP of 192.168.0.64, work LAN IP, the Z5 DOES NOT update the notebook to the 192.168.1.104 IP. It just leaves the .0.64 IP and moves on.
I'm headed home. I'll post back in about 3 hours.
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dslpartner
join:2005-02-18
| reply to Brano
said by Brano :I've just brought my laptop from work to home. I've put it to suspend at work and later plugged to my home network running ZyWall5 with static DHCP entry for my laptop. The IP got renewed automatically as expected. This did not work prior XD.1 firmware. From my point of view the DHCP bug is gone. Would you mind getting a packet capture next time you do this, so we can compare it to the packet capture Shootist will get when it fails.
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The real downside of GIT may be that _my_ way of doing things is quite possibly very rare. But it clearly is the only right way. The fact that everybody else does it some other way only means that they are wrong. -Linus |
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Brano
I hate Vogons
Premium,MVM
join:2002-06-25
Burlington, ON
·TekSavvy Solutions..
| reply to Shootist
I've just brought my laptop from work to home.
I've put it to suspend at work and later plugged to my home network running ZyWall5 with static DHCP entry for my laptop.
The IP got renewed automatically as expected. This did not work prior XD.1 firmware.
From my point of view the DHCP bug is gone. |
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Anav
Sarcastic Llama? Naw, Just Acerbic
Premium
join:2001-07-16
Dartmouth, NS | reply to dslpartner
Anybody with enough money to send dslpartner for a one-way trip to the moon? |
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