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DHCP from Server and Router
16 years 8 months ago #25216
by SteveP
DHCP from Server and Router was created by SteveP
I'm doing CCNA v3.1 and DHCP configuration doesn't come into the syllabus (our tutor said not). Suppose I set up a router and a W2K3 server, each providing a pool of IP addresses and they are connected to a switch. I attach an XP client (configured to obtain the IP address automatically) to the switch, so the question is "which takes precedence in providing the IP address - the router or the W2K3 server?". I guess it doesn't really matter, so long as the client gets an address, but I'm just interested to know how a conflict is resolved.
I don't have access to a server, otherwise I'd set this up and test it for myself.
I don't have access to a server, otherwise I'd set this up and test it for myself.
16 years 8 months ago #25218
by Smurf
Wayne Murphy
Firewall.cx Team Member
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Now working for a Security Company called Sec-1 Ltd in the UK, for any
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Replied by Smurf on topic Re: DHCP from Server and Router
Its really simple Steve, the one that gets the reply back the quickest, hehe.
Thats basically it........It uses a broadcast mechanism (sent to broadcast address) so both devices will get the request and will respond.
Cheers
Thats basically it........It uses a broadcast mechanism (sent to broadcast address) so both devices will get the request and will respond.
Cheers
Wayne Murphy
Firewall.cx Team Member
www.firewall.cx
Now working for a Security Company called Sec-1 Ltd in the UK, for any
Penetration Testing work visit www.sec-1.com or PM me for details.
16 years 8 months ago #25226
by SteveP
Replied by SteveP on topic Re: DHCP from Server and Router
Pah - so simple! I assumed that there must be some clever algorithm or other reason that one would take priority. I was just thinking at a "higher" level.
I realise that a DHCP request involves a broadcast (the "DORA" acronym springs to mind) so, if the server was on the other side of the router (a different LAN to the client), it would be the router which supplied the address becasuse the router wouldn't forward the broadcast from the client.
Thanks for clearing it up for me.
I realise that a DHCP request involves a broadcast (the "DORA" acronym springs to mind) so, if the server was on the other side of the router (a different LAN to the client), it would be the router which supplied the address becasuse the router wouldn't forward the broadcast from the client.
Thanks for clearing it up for me.
16 years 8 months ago #25243
by Ozzy_98
Replied by Ozzy_98 on topic Re: DHCP from Server and Router
If the DHCP server was on the otehr side of a router, then by default, you wouldn't get DHCP addresses, since routers do not forward broadcasts. Also remember too, there's IP broadcasts (Sent to the last IP address in a range, the 192.168.1.255 for example on the 192.168.1.0 network) and there's physical broadcasts (Sent to the FF:FF:FF:FF mac address)
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16 years 8 months ago #25401
by Datacom_guy
Replied by Datacom_guy on topic Re: DHCP from Server and Router
If the DHCP server was on the other side of a router, then the router needs to set up as a DHCP Relay agent, so that it can forward the DHCP Request.
Thanks,
Datacom_guy
Thanks,
Datacom_guy
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