Another method for the check can be gratuitous arp. This would not be restricted by firewalls.
Phil Priest CCIE #39930 Sent from my iPhone On 8 Jan 2014, at 20:28, "Ron Marosko" <[email protected]<mailto:[email protected]>> wrote: Do keep in mind that even with a ping check, certain client devices (especially Microsoft with firewall enabled) will not respond to an ICMP echo packet, thus leading the DHCP server to infer that an address is available when, technically, it is not… and thus leading to duplicate address error messages as well. It’s one of those pains that we just have to learn to work around. Rgds, Ron -- Ron Marosko, Jr. . . . . . . . . . . . . . . . . . . . . . . . . . . CCIE No. 4526 (R/S), CWNA, ACMA, NN5DX <image001.gif> Consulting Network Architect Global Technology Resources,Inc. 1108 West Dickinson Blvd, Suite A Fort Stockton, TX 79735 USA o: +1 432 336 5600 x110 c: +1 432 290 6344 e: [email protected]<mailto:[email protected]> pgp pubkey: 0x58AB8B5C<http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x778B3B0258AB8B5C> "To know me is to fly with me." This message contains confidential information and is intended only for the individual named. Please notify the sender immediately by e-mail if you have received this e-mail by mistake and delete this e-mail from your system. Any opinions presented in this email are solely those of the author and do not necessarily represent those of the company. E-mail transmission cannot be guaranteed to be secure or error–free; the sender therefore does not accept liability for any errors or omissions in the contents of this message, which arise as a result of e–mail transmission. Diese Nachricht enthält vertrauliche Informationen und ist nur für den einzelnen, namentlich genannten gedacht. Bitte benachrichtigen Sie den Absender umgehend per E-Mail, wenn Sie diese E-Mail irrtümlich erhalten haben und löschen Sie diese E-Mail aus Ihrem System. Alle Meinungen in dieser E-Mail die vorgestellt werden sind ausschließlich die des Autors und nicht unbedingt die des Unternehmens. E-Mail-Übertragung kann nicht garantiert werden, sicher oder fehlerfrei sind; der Absender übernimmt daher keine Haftung für irgendwelche Fehler oder Auslassungen in den Inhalten dieser Nachricht, die als Ergebnis der E-Mail-Übertragung ergeben. 此消息包含机密信息，并仅用于指定的个人。通过e-mail，请立即通知发件人如果您误收到此电子邮件，并从您的系统中删除此电子邮件。这封电子邮件中提出的任何意见仅仅是那些作者，并不一定代表公司。发送E-mail不能保证是安全或无差错，因此，发件人在该消息的内容，电子邮件传输的结果产生任何错误或遗漏不承担责任。 From: [email protected]<mailto:[email protected]> [mailto:[email protected]] On Behalf Of Michael Ruetz Sent: Wednesday, January 08, 2014 10:32 AM To: Jeff Rensink; Justin Kurynny Cc: [email protected]<mailto:[email protected]> Subject: Re: [OSL | CCIE_Wireless] DHCP on IIOS Hi again, Thx. to both of you, solution one was my favorite too. :) The PING-check you (Jeff) mentioned is new to me (as so much other stuff), sounds interesting. Greetings from Austria … MICHAEL RUETZ Senior IT Architekt/Engineering Manager, CCIE#5356 R/S Von: Jeff Rensink <[email protected]<mailto:[email protected]>> Datum: Mittwoch, 08. Jänner 2014 17:08 An: Justin Kurynny <[email protected]<mailto:[email protected]>> Cc: Michael Ruetz <[email protected]<mailto:[email protected]>>, "[email protected]<mailto:[email protected]>" <[email protected]<mailto:[email protected]>> Betreff: Re: [OSL | CCIE_Wireless] DHCP on IIOS I agree with Justin. The switches will do a check (I'm guessing it's a ping) before handing out an IP address. But why run the risk of an accidental duplicate address. Regards, Jeff Rensink : Sr Instructor : iPexpert<http://www.ipexpert.com/> CCIE # 24834 :: Wireless / R&S :: World-Class Cisco Certification Training Direct: +1.810.326.1444 :: Free Videos<http://www.youtube.com/ipexpertinc> :: Free Training / Product Offerings<http://www.facebook.com/ipexpert> :: CCIE Blog<http://blog.ipexpert.com/> :: Twitter<http://www.twitter.com/ipexpert> On Wed, Jan 8, 2014 at 12:17 AM, Justin Kurynny <[email protected]<mailto:[email protected]>> wrote: Michael, I’d personally go with the first option unless otherwise instructed by the exam. You know that in real life you probably wouldn’t do it the second way, especially considering conflicts could occur (yes, I know the lab isn’t real life). The argument here is that I don’t like to leave anything to chance in the lab and you don’t want to be troubleshooting a self-inflicted DHCP/IP conflict issue on top of everything else you’re already doing. It’s slightly more configuration work, but because IOS doesn’t offer a DHCP clustering/LB mechanism, I’d just split the pools. Justin From:[email protected]<mailto:[email protected]> [mailto:[email protected]<mailto:[email protected]>] On Behalf Of Michael Ruetz Sent: Tuesday, January 07, 2014 21:45 To: [email protected]<mailto:[email protected]> Subject: [OSL | CCIE_Wireless] DHCP on IIOS Dear Wireless-Guys, I though about setting up a redundant DHCP-Service running on two IOS-Devices while preparing for the lab (in march), and came up with two solutions: — split the DHCP-pools in half on the two boxes — configure both devices with the same (!) pool of addresses, and leave it to the client’s duplicate-adress-check to resolve any issues Any recommendations from your side would be very welcome. Best regards … MICHAEL RUETZ Senior IT Architekt/Engineering Manager, CCIE#5356 _______________________________________________ Free CCIE R&S, Collaboration, Data Center, Wireless & Security Videos :: iPexpert on YouTube: www.youtube.com/ipexpertinc<http://www.youtube.com/ipexpertinc> ________________________________ This message contains confidential information and is intended only for the individual named. Please notify the sender immediately by e-mail if you have received this e-mail by mistake and delete this e-mail from your system. Any opinions presented in this email are solely those of the author and do not necessarily represent those of the company. E-mail transmission cannot be guaranteed to be secure or error–free; the sender therefore does not accept liability for any errors or omissions in the contents of this message, which arise as a result of e–mail transmission. _______________________________________________ Free CCIE R&S, Collaboration, Data Center, Wireless & Security Videos :: iPexpert on YouTube: www.youtube.com/ipexpertinc<http://www.youtube.com/ipexpertinc>
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