On Friday 13 February 2004 8:22 pm, James Knott wrote:
Paul W. Abrahams wrote:
Can anyone offer an opinion on the pros and cons of using DHCP versus fixed IP addresses to set up the IP addresses for my small local network? Or point me to a document on the subject? DHCP requires a server. Static requires configuration of each computer.
I assume that if I install (and start) dhcpd on one of my machines, then any other machine that joins the net and asks for a DHCP address will get one and be on the net also, right? I also assume that if I were to be so foolish as to have dhcpd running on two machines on the network, the two copies would get into an electronic cockfight. Paul Abrahams
Paul W. Abrahams wrote:
On Friday 13 February 2004 8:22 pm, James Knott wrote:
Paul W. Abrahams wrote:
Can anyone offer an opinion on the pros and cons of using DHCP versus
fixed IP
addresses to set up the IP addresses for my small local network? Or point
me
to a document on the subject?
DHCP requires a server. Static requires configuration of each computer.
I assume that if I install (and start) dhcpd on one of my machines, then any other machine that joins the net and asks for a DHCP address will get one and be on the net also, right?
It should be able to support as many computers as you have addresses available.
I also assume that if I were to be so foolish as to have dhcpd running on two machines on the network, the two copies would get into an electronic cockfight.
Actually no. DHCP is designed so that multiple servers can respond to a request, but the client chooses the first response received.
On 02/14/2004 09:27 AM, Paul W. Abrahams wrote:
I assume that if I install (and start)
AND configure.
dhcpd on one of my machines, then any other machine that joins the net and asks for a DHCP address will get one and be on the net also, right?
Yes and no. DHCP configures the client to correctly run on your network. For that machine (and any other) to be 'on the net' you need to NAT, easily done with SuSEfirewall2. If you already have masquerading working, then when the DHCP server configures the client, it is 'on the net' yes.
I also assume that if I were to be so foolish as to have dhcpd running on two machines on the network, the two copies would get into an electronic cockfight.
You would have problems, yes. -- Joe Morris New Tribes Mission Email Address: Joe_Morris@ntm.org Web Address: http://www.mydestiny.net/~joe_morris Registered Linux user 231871 God said, I AM that I AM. I say, by the grace of God, I am what I am.
I also assume that if I were to be so foolish as to have dhcpd running on two machines on the network, the two copies would get into an electronic cockfight.
You would have problems, yes.
Another guy said it will not have problem since client is first come first serve basis.. once the comptuer gets the ip it will not request for one. Anyone test thsi out and the results? henry
On Sat, 14 Feb 2004 16:06, Henry Tang wrote:
I also assume that if I were to be so foolish as to have dhcpd running on two machines on the network, the two copies would get into an electronic cockfight.
You would have problems, yes.
Another guy said it will not have problem since client is first come first serve basis.. once the comptuer gets the ip it will not request for one. Anyone test thsi out and the results?
henry
It depends on the lease time specified in your configuration file. Once the lease time has expired the IP address can/will be reassigned to the next computer logging on which has had its lease time expired or a is new computer connection. -- Regards, Graham Smith ---------------------------------------------------------
I also assume that if I were to be so foolish as to have dhcpd running on two machines on the network, the two copies would get into an electronic cockfight.
You would have problems, yes.
Another guy said it will not have problem since client is first come first serve basis.. once the comptuer gets the ip it will not request for one. Anyone test thsi out and the results?
henry In general, I hate RTFM replies to people's questions. I certainly don't know
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On Saturday 14 February 2004 12:06 am, Henry Tang wrote: the answer to your question. I hope someone who does know the answer can provide more insight than I can. But, from my experience working with similar services such as WINS, you would do well to find the specification, or an expert description of the protocol and read it. IIRC, DHCP is an IETF RFC. You should be able to find it here: http://www.ietf.org/rfc.html There is a chance I'm wrong about the IETF part. The RFC's I've looked at are often not overly intractable. I mean no disrespect by suggesting you read the formal documentation, I just believe it's the correct thing to do in your case. STH -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.2 (GNU/Linux) iD8DBQFALby+H2SF0i7rrGwRAtikAKClSdbsc1hYxX6kJLkcfmb9CSG2bACfRCFC T9gEUR6ZK2vpLZLVVLjLd2s= =QmcJ -----END PGP SIGNATURE-----
In general, I hate RTFM replies to people's questions. I certainly don't know the answer to your question. I hope someone who does know the answer can provide more insight than I can. But, from my experience working with similar services such as WINS, you would do well to find the specification, or an expert description of the protocol and read it. IIRC, DHCP is an IETF RFC. You should be able to find it here: http://www.ietf.org/rfc.html
There is a chance I'm wrong about the IETF part. The RFC's I've looked at are often not overly intractable. I mean no disrespect by suggesting you read the formal documentation, I just believe it's the correct thing to do in your case.
In this rare use of man (man dhcpd.conf) it does actually show some examples. I used the man pages to help sort out some of the config problems I was having when first starting to use DHCP. Ken
Henry Tang wrote:
I also assume that if I were to be so foolish as to have dhcpd running on two machines on the network, the two copies would get into an electronic cockfight.
You would have problems, yes.
Another guy said it will not have problem since client is first come first serve basis.. once the comptuer gets the ip it will not request for one. Anyone test thsi out and the results?
Multiple servers are often used on large networks. Here's some info from http://www.dhcp-handbook.com/dhcp_faq.html#cdsbe "20. Can a DHCP server back up another DHCP server? You can have two or more servers handing out leases for different addresses. If each has a dynamic pool accessible to the same clients, then even if one server is down, one of those clients can lease an address from the other server. However, without communication between the two servers to share their information on current leases, when one server is down, any client with a lease from it will not be able to renew their lease with the other server. Such communication is the purpose of the "server to server protocol" (see next question). It is possible that some server vendors have addressed this issue with their own proprietary server-to-server communication."
On Saturday 14 February 2004 7:32 am, James Knott wrote:
Multiple servers are often used on large networks.
Here's some info from http://www.dhcp-handbook.com/dhcp_faq.html#cdsbe
"20. Can a DHCP server back up another DHCP server?
You can have two or more servers handing out leases for different addresses. If each has a dynamic pool accessible to the same clients, then even if one server is down, one of those clients can lease an address from the other server.
However, without communication between the two servers to share their information on current leases, when one server is down, any client with a lease from it will not be able to renew their lease with the other server. Such communication is the purpose of the "server to server protocol" (see next question). It is possible that some server vendors have addressed this issue with their own proprietary server-to-server communication."
First of all, I'll admit right off that for me this is now a matter of intellectual curiosity, not a practical problem, since I have no plans to install multiple DHCP servers. But the implication of the quote above is that if there are two DHCP servers on the net, they should assign non-overlapping address ranges. Is that correct? And if so, can the servers get into a fight if the address ranges do overlap, with each server handing out the same address x to a different client? (Actually, the fight would then be between the clients, I suppose.) Paul Abrahams
Paul W. Abrahams wrote:
On Saturday 14 February 2004 7:32 am, James Knott wrote:
Multiple servers are often used on large networks.
Here's some info from http://www.dhcp-handbook.com/dhcp_faq.html#cdsbe
"20. Can a DHCP server back up another DHCP server?
You can have two or more servers handing out leases for different addresses. If each has a dynamic pool accessible to the same clients, then even if one server is down, one of those clients can lease an address from the other server.
However, without communication between the two servers to share their information on current leases, when one server is down, any client with a lease from it will not be able to renew their lease with the other server. Such communication is the purpose of the "server to server protocol" (see next question). It is possible that some server vendors have addressed this issue with their own proprietary server-to-server communication."
First of all, I'll admit right off that for me this is now a matter of intellectual curiosity, not a practical problem, since I have no plans to install multiple DHCP servers. But the implication of the quote above is that if there are two DHCP servers on the net, they should assign non-overlapping address ranges. Is that correct? And if so, can the servers get into a fight if the address ranges do overlap, with each server handing out the same address x to a different client? (Actually, the fight would then be between the clients, I suppose.)
The problem with overlapping ranges, would be possible conflicts between clients. However, as I understand it, modern dhcp servers check to see if someone has an address, before assigning it to someone else. I guess someone will have to fire up a network monitor and watch the transactions with various scenarios.
participants (7)
-
Graham Smith -
Henry Tang -
James Knott -
Joe Morris (NTM) -
Ken Schneider -
Paul W. Abrahams -
Steven T. Hatton