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Webcast-Catalyst9k
New Member

Prioritisng IP Helper-addresses

Hi Team,

I was wondering if anyone can give some answers to this....

is there anyway i can prioritise where to point broadcast address to?

Like e.g.

interface vlan 2

     ip address 10.1.2.1 255.255.255.0

     ip helper-address 10.1.1.50

     ip helper-address 10.1.1.80

the senario is like this:

i want 10.1.1.50 (pabx dhcp)to answer first to any dhcp request because its a PABX,and will provide connectivity for IP phones ,so now if the equipment is not a phone,  it will not hand out an ip for it. on the other hand a pc will get its ip from 10.1.1.80, since it knows that its a pc so gives it an ip.

other wise the 10.1.1.80 will try to give an ip address to the ip phone but the connection will fail since there's no tftp address

what i want is iphones and pc on the same LAN but different DHCP servers.

cheers.

3 REPLIES
Hall of Fame Super Gold

Re: Prioritisng IP Helper-addresses

No, you cannot do this. However you can configure a single DHCP server to correctly give addresees for all devices.

Note, in reality you should have the phones on a separate VLAN. Not doing so causes many problems.

New Member

Re: Prioritisng IP Helper-addresses

Hi Ioane,

What happens in your example is that the router sends the DHCP discovery to both DHCP servers. The first one to repond with an offer is the one your host will send a request to.

If I were in your shoes, I'd have both DHCP servers providing the same options but for different halves of each scope. IN addition to mitigting your issue, this give you a basic level of redundancy (although it cuts your address spacing in half). Althernatively, a clustered DHCP server would provide redundancy with full scope availaiblty.

HTH

Rgds

Scott

New Member

Re: Prioritisng IP Helper-addresses

Thank you Guys,

you've been a great help...i now know what needed to do...

Thank you again.

Regards

Ioane

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