Transcript PowerPoint

Network Protocols
Dynamic Host Configuration Protocol
(DHCP)
TDC375 Autumn 03/04
John Kristoff - DePaul University
1
Bootstrapping and auto-config
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Host loads boot image and/or config from network
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Station needs to know its own IP address
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Station only knows its hardware address
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Station minimally needs:
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Its IP address
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The default gateway/router
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Its subnet mask
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...and a DNS server (or more) would be nice
TDC375 Autumn 03/04
John Kristoff - DePaul University
1
Older, less popular methods
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Reverse ARP (RARP)
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ICMP info/mask/router queries
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What is the IP address for MAC xxxx.yyyy.zzzz
What is my IP, mask and router?
BOOTP
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What is my config (and maybe boot loader file)?
TDC375 Autumn 03/04
John Kristoff - DePaul University
1
To get configuration remotely
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Broadcast request
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no source IP yet, use 0.0.0.0 (this net, this host)
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destination? use 255.255.255.255 (limited
bcast)
Receive response
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From a configuration server
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Sends to our MAC, since we don't have a IP yet
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Routers can intercept/forward to remote servers
TDC375 Autumn 03/04
John Kristoff - DePaul University
1
Typical DHCP startup behavior
Client
Server
DHCP-DISCOVER->
<-DHCP-OFFER
DHCP-REQUEST->
<-DHCP-ACK
DHCP-RELEASE->
TDC375 Autumn 03/04
John Kristoff - DePaul University
1
DHCP packet format
TDC375 Autumn 03/04
John Kristoff - DePaul University
1