what is the need og
jitu(config)#ip helper address <ip address>
can any one exaplain it briefly
specially shain i am looking towards you.Becoz you are the
only one who can solve my that problem not even jitendera sinha
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Answer Posted / shahin
If u r talking about need of command: ip helper-address, thn
i can say about it.
In CCNA studies, we got to know that router always block the
broadcast traffic, dats fine.
But if ur organization's network is establish in such a way:
client-------Router------- DNS Server
!
!
!
!
DHCP Server
Now... if ur pc want to locate DNS server thro broadcast,
broadcast traffic will come from client pc to all the way to
Router.
Wat router will do now, Router will block all the broadacast
traffic. As we learn in our previous studies. Ryt....
So client PC will unable to locate DNS server, coz router
doesn't allow to broadcast the traffic.
Same case, if Client PC want to gain IP address, it will
broadcast...n requesting for IP address from DHCP server.
I hope u knw the DHCP process, I mean "DORA" process. In
this case also router block all the broadcast traffic.
So wats the solution for this....
By configuring IP address on the interface subconfig mode..
with the help of (ip helper-address A.B.C.D)....
wat it'll do, The UDP broadcasts traffics are translated
into a unicast by the router, making the communication
possible.
The command should be configured on the interface that will
be receiving the broadcasts.
Router(config)#interface fastethernet 0/0
Router(config-if)#ip helper-address A.B.C.D
where A.B.C.D is the IP address of ur DNS/DHCP server.
One more point is there, this ip-helper address doesn't
forward all the UDP broadcast.. it broadcast only 8 UDP
services.. like..
1. TIME, port 37
2. TACACS, port 49
3. DNS, port 53
4. BOOTP/DHCP Server, port 67
5. BOOTP/DHCP Client, port 68
6. TFTP, port 69
7. NetBIOS name service, port 137
8. NetBIOS datagram service, port 138
if u want to include any more UDp services the command is
Router(config)#ip forward-protocol udp (port Number)
Hope this post helps u to understand the use of command n
circumstances of command when to use it n how to use it.
Looking forward ur feedback. If i did anymistake the let me
know plzzzzzzzzz...
Cheers.. hv a nice day buddy.
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