RE: DHCP Server - Default-router List

Ah I see where you are going with this now (hopefully). The IOS DHCP
server will just hand the address you defined in the order your define
them, I don't know of any options you can use in the IOS DHCP that would
say if default router 1 is down, then hand out default router 2. Some
devices can receive multiple default gateways and utilize some type of
intelligence to prefer one gateway over the other for example up/down.
Windows clients on the other hand will accept the first default gateway
it receives and apply a binding order in order received (if no metrics
are set to them). I would guess you would need a software application
that could tell the clients if gateway 1 is unreachable then use gateway
2, but from what I understand out of the box it doesn't. Hopefully I
answered your questions, if not someone else may be of help.

From: Tom Kacprzynski [mailto:tom.kac_at_gmail.com]
Sent: Friday, November 19, 2010 1:16 PM
To: Mahaffey, Brian
Cc: Cisco certification
Subject: Re: DHCP Server - Default-router List

Brain,
Thank you for your response. I'm trying to figure out what is the
feature for in the DHCP server. How could a DHCP server give out up to 8
IP addresses that can be used as a default route. Yes HSRP would work
great to provide first hop redundancy, but why would cisco provide the
option of giving out 8 IP addresses if the client will take the first
address. As far as i could see, yes it does take the first one, even if
that first one is not reachable, so no arp or icmp ping for it from the
client.

Regards,

Tom

On Fri, Nov 19, 2010 at 3:09 PM, Mahaffey, Brian <bmahaffey_at_pelco.com>
wrote:

Have you looked into HSRP and just giving the clients one default
router? I would assume the client would accept the first one it
receives, but I am just guessing.

-----Original Message-----
From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
Tom Kacprzynski
Sent: Friday, November 19, 2010 12:50 PM
To: Cisco certification
Subject: Re: DHCP Server - Default-router List

Anyone, please? I'm stuck.

thanks

On Thu, Nov 18, 2010 at 7:21 PM, Tom Kacprzynski <tom.kac_at_gmail.com>
wrote:

> Hello,
> Just a quick question regarding IOS DHCP server and the default-router
> list.
>
> If I have a pool that specifies multiple default routers, but what I
don't
> understand is how does the client pick one of the other?
>
> Sample config below.
>
> Rack1R1#sh run | s pool
> ip dhcp pool TEST
> network 155.1.146.0 255.255.255.0
> default-router 155.1.146.10 155.1.146.1
> dns-server 155.1.146.1
>
> Based on this the client takes the first IP address for default
router,
> even if that router is not reachable it does not failover.
>
> Does anyone know how you could use the two IP addresses and how does
the
> client switch between them?
>
> Thank you,
>
> Tom Kacprzynski

Blogs and organic groups at http://www.ccie.net
Received on Fri Nov 19 2010 - 13:28:14 ART