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Daniel, I’d also like to add to Godswill’s response that since by default a Cisco router acting as a DHCP server will ping each address before leasing it out it will not lease out an HSRP virtual address because HSRP virtual addresses are pingable, but what about a VRRP virtual address?
Also I thought this was interesting - did you know that with VRRP you can actually assign one of the router’s physical interface addresses as the virtual address?
Brian L.
—–Original Message—– From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Godswill Oletu Sent: Friday, July 07, 2006 8:39 AM To: Daniel Ramirez Cc: ccielab@groupstudy.com Subject: Re: DHCP server excluded address
Daniel,
By default the DHCP server pings a pool address before assigning a particular ip address to a requesting client. If the ping is unanswered after 2 pings of 500ms timeouts each, the DHCP server assumes that the address is not in use & assigns it. You can change this default behaviour by configuring ‘ip dhcp ping ‘
The DHCP server assumes that all ip addresses in the pool subnet are available for assignment to clients, so configuring the exclude range is a good design practice to define what is available & what is unavailable. Since, you already know of some unavailable ip addresses, why not go ahead and let the dhcp server know about those unavailable ip addresses? It will helps to reduce the range of ip addresses, the dhcp sever have to check before assigning an ip address. Also, you will increase the chances of not getting a duplicate ip address.
I really do not see it as an overconfiguration.
Godswill Oletu CCIE #16464
—– Original Message —– From: “Daniel Ramirez” To: “Godswill Oletu” Cc: Sent: Friday, July 07, 2006 7:56 AM Subject: Re: DHCP server excluded address
> Thanks for your reply. > > I know that excluding local IP address and virtual IP address It will > work. But I have checked that without configuring the command: “ip > dhcp excluded-address” it also works (that is, the router that acts as > dhcp server doesn’t assign the local ip address or the hsrp virtual > ip). So I am not sure if I am overconfiguring the router if I > explicitly configure the excluded address. > > Regards > DRA > > > On 7/7/06, Godswill Oletu wrote: > > Daniel, > > > > Yes, exclude all used ip addresses including the virtual ip address of the > > HSRP. > > > > HTH > > > > Godswill Oletu > > CCIE #16464 > > > > > > —– Original Message —– > > From: “Daniel Ramirez” > > To: > > Sent: Friday, July 07, 2006 3:05 AM > > Subject: DHCP server excluded address > > > > > > > Hi, > > > > > > When configuring dhcp server, is it necessary to excluded the local > > > address of the router from the avalaible address pool?. Also, when > > > configuring both HSRP and DHCP server feature in the same router, I > > > assume that it is necessary to excluded also the HSRP virtual ip, is > > > it rigth ? > > > > > > Best Regards, > > > DRA > > > > > >