CompTIA Network+ Certification Exam Tutorial DHCP and DHCP Relay Agents
March 26th, 2008As a CompTIA Network+ communicating candidate, you’re belike older with DHCP - but meet in case, we’re feat to analyse DHCP principle here and then go into a communicating of DHCP Relay Agents.
When it comes to distribution an IP become to every the PCs on our network, along with their meshwork mask, DNS computer location, and more, we’ve got digit choices on how to do it:
Go to every workstation and configure the workstation statically
Go to every workstation and configure them every to ingest DHCP
What we hit here is the artist “static vs. dynamic” argument. I don’t poverty you to conceive I’m lazy, but I’ll verify the impulsive artefact of doing things nearly every azygos time.
You haw astonishment ground it matters, since both methods refer temporary apiece workstation. You’re correct most that, and modify though it’s a aggregation quicker to configure a workstation to intend its IP become and cover from a DHCP computer than it is to configure the whole IP become and cover statically, the actual benefits become in when the meshwork changes.
And verify it from me - your meshwork module change. You’ll vanish hosts, you’ll add hosts, and if the preceding meshwork trainer didn’t organisation for forthcoming growth, the period haw become when you’ve got to modify the IP listing plot for your network. The pick that was prefabricated originally between noise plan and DHCP module then watch how cushy the modify module be.
If the meshwork was statically configured, you module today hit to go to every azygos workstation and modify their IP addressing to the newborn scheme.
If the meshwork is using DHCP, you only modify the networking plot on the DHCP computer and earmark the workstations to intend their newborn addresses dynamically.
Believe me, I’ve performed IP become changes in both fashions, and I’ll verify DHCP every time! Avoiding noise IP become assignments also cuts downbound on the chances of digit hosts in your meshwork existence appointed the aforementioned IP address.
When hosts obtain an IP become from DHCP, it does not belong to that patron permanently. The become is actually leased from a DHCP server. Let’s achievement finished the DHCP impact from the host’s saucer of view.
First, the DHCP Client boots up, and sends a DHCP Discover boat onto the network. The patron does this in visit to “Discover” a DHCP computer or servers. This Discover boat is a Level 3 broadcast, which has a instruction IP become of 255.255.255.255.
Every DHCP Server that hears this programme module move with a DHCP Offer, and it’s an IP become and cover that is existence offered. The DHCP Offer also includes a subnet mask, the IP become of the DHCP Server sending the response, and how daylong the patron crapper ready this become (the DHCP engage duration).
If binary DHCP Servers hap to center this broadcast, they module apiece substance an IP address.
The DHCP Client module accept the prototypal substance it receives. It does so by sending added broadcast, a DHCP Request packet.
The DHCP Server that prefabricated the substance that’s existence acknowledged module today beam a DHCP Acknowledgement, which contains the rest of the aggregation the patron needs to function, including the positioning of a DNS server. The DHCP Server that prefabricated the substance that was not acknowledged module convey the offered IP become to its arrange of negotiable addresses, its become pool.
I prefabricated individual mentions in this country most these DHCP packets existence broadcasts. Do you advert which meshwork connectivity figure does not nervy broadcasts? That’s right, it’s our older friend, the router!
If a PC is on digit lateral of the router and the DHCP Server is on added side, we’ve got a problem. The initial DHCP Discover boat is a broadcast, and the router module not nervy that programme to the DHCP Server. Luckily, this doesn’t stingy that we requirement a DHCP computer on every azygos subnet on the network, because we crapper configure the router as a DHCP Relay Agent.
A DHCP Relay Agent module nervy DHCP Requests to the DHCP Server. You crapper also configure a Windows computer as a DHCP Relay Agent. Naturally, the Relay Agent staleness be on the aforementioned fleshly portion as the hosts that cannot accomplish the DHCP Server - never place it on the aforementioned portion as the DHCP Server itself.
Configuring a router as a DHCP Relay Agent is a aggregation assorted than configuring a Windows server, and your Network+ communicating module not order you to configure either. You should undergo ground the requirement for a Relay Agent exists, though, and should you requirement to configure digit on your network, ever analyse the vendor’s documentation.
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