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Superscopes
- Thread starter 1665
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- #3
Thanks, so let me clear this up, so I have one scope at the moment with is for our 300 users in our main office, our remote offices obviously have completely different IP ranges, so do I create separate scopes for each office and put them is one superscope together and just leave the LAN scope on it's own? Also how do remote offices know how use the correct scope and not one of the other ones?
Kind Regards
Andy
Kind Regards
Andy
GrnEyedLdy
Instructor
1665,
Mark Minasi explains it well...
"If a DHCP server serves several subnets and its adjacent routers support bootp forwarding, the server must expect to receive DHCP discover broadcasts from any one of those subnets. So how does the DHCP server know which subnet the broadcast came from--how does the server know which subnet range to draw from when assigning an IP address to a client?
The answer lies in how bootp forwarding works. A bootp forwarding-enabled router will retransmit (forward) a DHCP discover broadcast. But when this router forwards the broadcast, it adds data, a note saying, "To anyone who hears this: This is a broadcast that I originally found on a different subnet, subnet x.y.z.a." Then, if a DHCP server receives a broadcast that was retransmitted over one or more routers, the server will know what subnet to direct the response back to and which scope to pull a number from for its offer".
Here is the link in case the rest of the article interests you.
Hope this helps,
Patty![[ponytails2]](/data/assets/smilies/ponytails2.gif "[ponytails2] [ponytails2]")
Mark Minasi explains it well...
"If a DHCP server serves several subnets and its adjacent routers support bootp forwarding, the server must expect to receive DHCP discover broadcasts from any one of those subnets. So how does the DHCP server know which subnet the broadcast came from--how does the server know which subnet range to draw from when assigning an IP address to a client?
The answer lies in how bootp forwarding works. A bootp forwarding-enabled router will retransmit (forward) a DHCP discover broadcast. But when this router forwards the broadcast, it adds data, a note saying, "To anyone who hears this: This is a broadcast that I originally found on a different subnet, subnet x.y.z.a." Then, if a DHCP server receives a broadcast that was retransmitted over one or more routers, the server will know what subnet to direct the response back to and which scope to pull a number from for its offer".
Here is the link in case the rest of the article interests you.
Hope this helps,
Patty
A superscope is not what you need.
A superscope creates a larger group of addresses for use on a single LAN segment. Use a scope for each different network ID--LAN segment. So, for each remote site create a separate scope.
Let me see if I can explain it.
A scope is for a range of network addresses; be it all the addresses of the network ID or a partial range of them. When you exceed the number of available addresses, i.e 254 addresses in a class C network, you can create a superscope by adding another network ID to the first network ID and masking it to look like one network ID. By masking the 2 class C networks, you can create one larger network of 510 addresses.
The problem comes when you introduce a router into the picture--as in your case. By nature, a router will not forward broadcast from one LAN segment to another. This is why you need a relay agent or a bootp forwarder.
A relay agent is created on the local segment (network) and listens for DHCP specific broadcasts. It converts the broadcast to a unicast and sends it to the programmed DHCP server directly. The DHCP server notes the relay agents address and determines the network ID of which it came from and serves an address from the proper scope.
On the other hand, a bootp forwarder is an early version of relay agent. It is a configuration on a router that tagged and passed the broadcast onto the next segment. Eventually it got to the DHCP server and the server would see what network it had originally started from and issue a proper scope address.
One of the problems with bootp forwarding, depending on the hardware on the network, is that every device hears this and sometimes you would end up with multiple DHCP requests from the same device going to the DHCP server. This created more network traffic, all broadcast based.
I hope this helps.
bob
A superscope creates a larger group of addresses for use on a single LAN segment. Use a scope for each different network ID--LAN segment. So, for each remote site create a separate scope.
Let me see if I can explain it.
A scope is for a range of network addresses; be it all the addresses of the network ID or a partial range of them. When you exceed the number of available addresses, i.e 254 addresses in a class C network, you can create a superscope by adding another network ID to the first network ID and masking it to look like one network ID. By masking the 2 class C networks, you can create one larger network of 510 addresses.
The problem comes when you introduce a router into the picture--as in your case. By nature, a router will not forward broadcast from one LAN segment to another. This is why you need a relay agent or a bootp forwarder.
A relay agent is created on the local segment (network) and listens for DHCP specific broadcasts. It converts the broadcast to a unicast and sends it to the programmed DHCP server directly. The DHCP server notes the relay agents address and determines the network ID of which it came from and serves an address from the proper scope.
On the other hand, a bootp forwarder is an early version of relay agent. It is a configuration on a router that tagged and passed the broadcast onto the next segment. Eventually it got to the DHCP server and the server would see what network it had originally started from and issue a proper scope address.
One of the problems with bootp forwarding, depending on the hardware on the network, is that every device hears this and sometimes you would end up with multiple DHCP requests from the same device going to the DHCP server. This created more network traffic, all broadcast based.
I hope this helps.
bob
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