11-23-2006 12:24 AM - edited 03-05-2019 12:59 PM
Hi,
Can someone tell me what the effect of having multiple ip helper-address commands on the same interface is ?
Do the broadcasts get "load balanced" to each of the IP's in turn, do they get send to the second IP if the first is down or do they just get sent to both IP's all of the time?
Thanks,
Ellis
Solved! Go to Solution.
11-23-2006 02:11 AM
Hi Edixon,
The broadcast will only reach till the layer 3 interface where multiple helper address is configured bur after that it will be a unicast to multiple DHCP addresses whatever is configured in ip helper command and as Narayan updated the DHCP request will go to each and every DHCP server what is configured in helper address command and all the servers will reply and it depends on client which one to take.
HTH
Ankur
*Pls rate all helpfull post
11-23-2006 07:35 AM
Ellis
Yes, if you have configured two helper addresses and a broadcast packet comes in the interface then two copies will be transmitted (one to each of the addresses configured in the helper address). There is not any alternation or anything like that - a copy sent to each helper destination every time.
HTH
Rick
11-23-2006 12:47 AM
Hi,
I beleive that the effect will be the same as when you have multiple DHCP servers on your LAN segment. I don't think that there will be any real "load balancing".
//Mikhail Galiulin
11-23-2006 01:01 AM
Hi Friend,
Having multiple helper address doesn't really load balance.
When a user sends a DHCP broadcast it is relayed to both the DHCP server.
Both the servers then send the response which is forwarded to the host
Now the client choses the DHCP server and sends a DHCP request.
HTH, rate if it does
Narayan
11-23-2006 01:19 AM
So to clarify, the effect will be all broadcasts will get directed to both addresses all of the time?
11-23-2006 02:01 AM
HI
In addition i would like to put it like this.The reason to have multiple DHCP servers is redundancy.one server acting as primary and the other secondry.so if one server is out the other can serve client requests for address.
Thanks
Mahmood
11-23-2006 03:17 AM
Hi,
Nobody has answered my original question !!!!!
What is the effect of having multiple ip helper-address commands on a single interface?
Is it that broadcasts get sent as directed unicasts to ALL of the IP's listed on the ip helper lines ALL of the time?
11-23-2006 02:11 AM
Hi Edixon,
The broadcast will only reach till the layer 3 interface where multiple helper address is configured bur after that it will be a unicast to multiple DHCP addresses whatever is configured in ip helper command and as Narayan updated the DHCP request will go to each and every DHCP server what is configured in helper address command and all the servers will reply and it depends on client which one to take.
HTH
Ankur
*Pls rate all helpfull post
11-23-2006 02:22 AM
It is not a broadcast once it hits the router , it gets modified into a directed unicast in the case of a specific helper address or a directed broadcast in which case the router at the far end will turn it back into a broadcast if the helper address is like 10.2.3.255 then everyone on the far end subnet will hear and the dhcp server on that subnet will reply .
11-23-2006 02:26 AM
Glen,
Thanks for the clarification.
To clarify again : The original broadcast will get sent as a directed unicast to both of the addresses specificed by the IP Helper-Address commands?
Thanks,
Ellis
11-23-2006 07:35 AM
Ellis
Yes, if you have configured two helper addresses and a broadcast packet comes in the interface then two copies will be transmitted (one to each of the addresses configured in the helper address). There is not any alternation or anything like that - a copy sent to each helper destination every time.
HTH
Rick
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