01-22-2014 04:08 AM - edited 03-16-2019 09:22 PM
DHCP- Dynamic Host configuration protocol
DHCP is also known as BOOTP
DHCP uses DORA process
---------------------------------------
D- DHCP Discover Packet to the DHCP Server
O- DHCP Offer packet to the DHCP Client
R- DHCP Request to the DHCP Server
A- DHCP Ack to to the DHCP Clent
----------------------------------------------Some IMP Questions and answers--------------------------
Q. IF DHCP server is on another network then how IP phone get IP address?
When IP Phone reboot or Connected to Switch IP Phone send DHCP request to DHCP server, If
DHCP server is not available and Router connected to IP Phone configured as IP Helper then
Router take request from IP Phone and send request to DHCP server connected to other network.
To allocate IP address with correct IP pool router send IP address of interface, on which interface
request is received.
Q. Define DHCP OPTION
DHCP is also configure for device with more information called option.
IP Address From Scope 192.168.1.23
Subnet MASK Option 1 255.255.255.000
Default Gateway Option 3 192.168.1.1
DNS Server Option 6 8.8.8.8
SIP Server Option 120 192.168.87
TFTP Server Option 150 192.168.1.88
VLAN ID(802.1Q) Option 132 2
L2 802.1p Priority Option 133 6
L3 Priority Option 134 46
BOOTTP/DHCP option
http://www.networksorcery.com/enp/protocol/bootp/options.htm
Q. Initial IP Discovery process start with Brodcast or Not ?
--> Yes
Q. How you can check IP config on Windwos? IT help to understand DHCP flow use Wireshark and interface with your LAN card.
--> Goto START/RUN CMD(Command line) > ipconfig /all >> gives current IP address,Subnet mask,default gateway, MAC address
ipconfig /Release >> Release IP Address After this command get IP address 0.0.0.0
ipconfig /Renew >> Get New IP Address After this command get new IP Address
Q. IF you have multiple subnet and single DHCP server then what needed on Network router to assist to give IP address.
--> IP Helper command must be configured on router, so router send reuest to DHCP server on another network.
Q. Group of IP address configured on DHCP server is called as ?
--> SCOPE
01-22-2014 04:43 AM
Hello Sandeep, in this case the ip request would be recieved from the same voice interface on which the ip helper-address was assigned.
By using the ip helper-address command, a router can be configured to accept a broadcast request for a UDP service and then forward it as a unicast to a specific IP address
Br
Nitin Kharbanda
01-22-2014 10:47 AM
Thanks for additional information
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