DHCP problems

[BFA6]

Hi,

I've got a 10.20 machine running DHCP. There are currently 67 free DHCP addresses, but I've got 4 handheld scanners, that cannot pick up a DHCP address.
If the scanners are given static addresses then they work fine. If we bring them to the office, they will pick up a DHCP address fine.
I don't know anything about DHCP, so am looking for any ideas.

Thanks,

Hilary

[Wodisch]

Hi,

what you could do is to configure the IP-addresses for those devices as "permanent leases", which means that your DHCP server will only deliver the fixed IP-addresses via DHCP, but only for those devices, and never for something else.

HTH,
Wodisch

[A. Clay Stephenson]

Hi Hilary:

First let me preface my remarks by saying I know nothing about handheld scanners. However, when you say that when you bring them 'in' to the office they receive a DHCP address and will always work if given a static IP address. When they are 'out' (wherever that is) are they attempting to connect to another subnet?

If so, that is almost certainly your problem. By default, DHCP broadcast requests are not routed across subnet unless specifically enabled at the router.

Food for thought, Clay

[BFA6]

When the scanners are in the office they are given the address of the DHCP server here.

Before they are shipped to site the DHCP server address is changed, to the address of the one at site.

Bizarrely I freed up more DHCP addresses, so that there were 67 free addresses, and 4 of the scanners have now picked up a DHCP address correctly.

Hilary

[Paul R. Dittrich]

Hilary,
Is it possible your problem is nothing but DHCP's normal behavior?

You said you were very low on adddresses, then after freeing up some addresses, some of the scanners were successful using DHCP.

After a DHCP lease expires, there is a period of time (called "tombstoning") when the address is not in use but not yet available for re-use. If the original system comes back online, it will get it's original DHCP address back during this tombstone period.
Only after the expiration of BOTH the original DHCP lease AND the tombstone time period is the address truly "free" to be re-assigned to anyone who asks.

Based on the information so far, my guess is that you actually had zero free DHCP addresses.

HTH,
Paul

[BFA6]

Paul,

When I had 45 free addresses (this was 45 addresses that were not in /etc/dhcpdb) the scanners wouldn't pick up an address.

I'm not really sure if the problem is DHCP itself, or if there is a problem with the scanners setup. Although saying that, they have now picked up addresses, so I guess it can't be the scanners, unless they require a number of DHCP addresses to be free in a consecutive range.

Very confused

Hilary

[sven verhaegen]

hi ,

You need to be sure your handheld devices do support the bootp/dhcp protocol suit , if that is the case then the reason you get this IP address reply is that any device that requires a ip address and gets it does this by sending a request the bootp protocol deamon, DHCP in fact is just and extention of bootp , the main difference is that bootp servers static addresses to devices while DHCP has a range of addresses it points to certain devices , if there are no static address set in your bootp/dhcp setup then the bootpd will go into the list o available dhcp adresses and just issue one to the requesting device .

There are 2 way getting around you handheld issue , if this is a HP-UX machine like you describe then the deamon handeling the boot request from all machines , PC or handheld scanners ,is the bootpd of the HP-UX . It handles the bootp requests as well as the DHCP ones , you could go into the bootptab file and add the mack addresse of your handhelds and stick a static IP on them , when they boot they will always have that IP , or as suggested in a previous post here work with the dhcptab file inserting a "permanent lease" for your 4 handheld devices .

personally I would go to the bootp as it is easier to setup , just enter a block in the bootptab file for each handheld stating its mac address and the IP it should get , if not read the man pages on bootpd as it holds data on bootp and dhcp and how to configure entried in bootptab and dhcptab files...

(if your issue is that the scanners need to have always the same IP for everyone to be able to use them remotely you could still use DHCP but consider working with dynamic DNS , then you could use a hostname to identify the scanners with a name and when it gets a new IP the DNS will update that IP and link it to the hostname that doesn't change)