Thanks for the info Ray, very interesting to note the real behavior of a DHCP request. However, I have to comment on the following, once again I do not know details nor I have ever even read anything about network programming.
On Tuesday 11 March 2003 01:51 am, -ray wrote: > no flame... but maybe you are over simplifying the process a bit. :) > the client will solicit all dhcp servers (DHCPDISCOVER), and will then > receive responses (DHCPOFFER) from all dhcp servers. why should all DHCP servers need to be addressed? We are only looking for a single IP which can be provided by any server. Seems like a waste of bandwith, memory, and available IPs( I imagine IPs become temporarily unavailable ). > perhaps all the > offers are stored in temp variables. after reviewing all offers the > client has the option to respond (DHCPREQUEST) to one and only one of the > offers. the rest of the servers that sent offers are left hanging. What is the criterion of the client to determine which IP is good enough? Does it matter? I would imagine that unless a specific network is desired any IP would do. If a particular network IP range is to be used ( is this possible? ) there must or should be a mechanism to identify the DHCP server providing that range of IPs. > if the chosen server approves the request it'll respond (DHCPACK) to say ok > and finish the dhcp session. When the client receives the ok, then it can > fill the "real" variables with ip addr/ network info, etc. Once again a waste of IP addresses. The DHCP server would have to have a time out to determine when to make an IP address available to someone else. I guess there could be a response stating I did not like your IP so keep it! But once again, even more bandwith for what is needed. Should the server approve or just make note of it, if it already offer the IP then it should assume it is taken unless the time out is reached. > > But of course I'm not disputing that Microsoft programmers are extremely > dumb... :). if they follow the standard, should be little room for > conflict, but we know how MS loves to "extend and embrace." > > -ray But or course, Thanks for the info, I was just thinking about the process but I am certain that if there was a better way it would have already been implemented. Alvaro Zuniga > > On Mon, 10 Mar 2003, Alvaro Zuniga wrote: > > Basically what I was saying is that the programmer would have to be > > extremely dumb in order to make software that would create a conflict. In > > which ever possible scenario, once an algorithm fills its variable with a > > value which seems good enough it stops, or should stop at this point. > > Even if it continued searching for a different DHCP server ( fail over ), > > due to the nature of the protocol, the new value retrieved from the > > second DHCP server would replace the the contents of the variable ( which > > was possibly undefined ). I doubt that anyone would set up a program > > using two variables to obtain an IP address( maybe microsoft with the > > purpose of bloating XP ). If for some weird reason two addresses would be > > retrieved from the DHCP servers, the first DCHP server would be short one > > IP address from its pool of IPs which should not be a problem. > > > > This is purely theoretical, I do even setup DHCP usually becuase I like > > to do things the hard way. I do realize the importance of DHCP for large > > networks. > > > > :-) > > > > please be gentle when you flame this posting, I can already feel it > > > > Alvaro Zuniga > > > > On Friday 07 March 2003 08:06 am, Scott Harney wrote: > > > Alvaro Zuniga <[EMAIL PROTECTED]> writes: > > > > I do not know to much about this but if your are using different > > > > address pools like you have stated this is how is see it: > > > > > > > > In order to have a conflict the DHCP discovery algorithm would have > > > > to find a second instance of the DHCP server after finding the first > > > > one :-) Sounds like a Microsoftian Alnorythm. > > > > > > It's not as uncommon as you might think. I set up failover DHCP > > > servers when I was employed at Charter using Cisco's CNR. It's also > > > possible to do this with ISC dhcpd. You can also have two machines > > > handing out different pools. The main thing is each machine needs to > > > be aware of the other's pools and leases. As long as the dhcp client > > > gets a valid lease, it doesn't know or care about the multiple DHCP > > > servers on the subnet. > > > > > > Regarding the original poster's issues, I would turn off one of the > > > DHCP servers in his subnet. There's really no reason to have two > > > running in a small office environment and it will make problem > > > resolution really hard for him to diagnose. > > > > _______________________________________________ > > General mailing list > > [email protected] > > http://oxygen.nocdirect.com/mailman/listinfo/general_brlug.net
