From: André Bersvendsen (an-bersv@xxxxxxxxx)
Date: Wed Jul 24 2002 - 15:58:10 GMT-3
>1) small time isolation between two areas, each with one router.
>-each router can give the same address to a "local" client.
>After the condition clears, you have conflicting addresses.
>
>
It is ok if two DHCP servers offer the same IP address to a client at
the same time.
This will also happend in normal operation with syncronised dhcp databases.
This messages is DHCPOFFER with a unique random 32-bit transaction IDs.
The client send a DHCPREQUEST with the transaction ID of the first
DHCPOFFER received.
Then the server that recognice the transaction ID send of a DHCPACK.
So only one of the servers will be the one that gave the address that
the client want to use. And one server know that the address was used
the other don't know anything and asumes that the client was not
intrested or got a IP address from somone else - it don't care - it did
not get any message from the client with it's transaction ID.
So this server will probebly try to use this address the next time but
will find ut with ping that it is in use. A DHCP servermust test with
ping first.
>2) two clients requesting addresses at the same time
>-one is served by each router, and turns to be the same address.
>(This would not be catched by the ping test, because the address
>is not yet in use at that time. It could be catched by any of the
>routers by seeing another server is offering the same address, but
>as this is UDP, this method is not safe, if at all implemented.)
>
That situation might happend if they send a DHCPDISCOVERY at the exact
same time.
I have to look in to it to find out the result.
If one server is faster then the other for both of the clients then it
is no problem.
If one server is faster for one of the clients and the other server for
the other client with the same scope it might happend that this two
clients can get the same IP address. Never heard of this problem but in
teory it is a intresting question.
This archive was generated by hypermail 2.1.4 : Sat Sep 07 2002 - 19:36:42 GMT-3