4** Sent from my Windows Mobile® phone. -----Original Message----- From: nanog-request@nanog.org <nanog-request@nanog.org> Sent: Saturday, March 20, 2010 8:00 AM To: nanog@nanog.org <nanog@nanog.org> Subject: NANOG Digest, Vol 26, Issue 106 Send NANOG mailing list submissions to nanog@nanog.org To subscribe or unsubscribe via the World Wide Web, visit https://mailman.nanog.org/mailman/listinfo/nanog or, via email, send a message with subject or body 'help' to nanog-request@nanog.org You can reach the person managing the list at nanog-owner@nanog.org When replying, please edit your Subject line so it is more specific than "Re: Contents of NANOG digest..." Today's Topics: 1. Re: ISC DHCP server failover (Mike) 2. Re: CRS-3 (Steve Meuse) 3. Re: CRS-3 (jim deleskie) 4. Re: ISC DHCP server failover (sthaug@nethelp.no) 5. Help with a 3561 debug (Jess Kitchen) ---------------------------------------------------------------------- Message: 1 Date: Fri, 19 Mar 2010 17:10:04 -0700 From: Mike <mike-nanog@tiedyenetworks.com> Subject: Re: ISC DHCP server failover To: "David W. Hankins" <David_Hankins@isc.org> Cc: nanog@nanog.org Message-ID: <4BA4125C.2090309@tiedyenetworks.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed David W. Hankins wrote:
On Wed, Mar 17, 2010 at 09:22:06AM -0500, Dan White wrote:
The servers stop balancing their addresses, and one server starts to exhibit 'peer holds all free leases' in its logs, in which case we need to restart the dhcpd process(es) to force a rebalance.
If restarting one or both dhcpd processes corrects a pool balancing problem, then I suspect what you're looking at is a bug where the servers would fail to schedule a reconnection if the failover socket is lost in a particular way. Because the protocol also uses a message exchange inside the TCP channel to determine if the socket is up (rather than just TCP keepalives) this can sometimes happen even without a network outage during load spikes or other brief hiccups on
<long explanation snipped> With all due respect and acknowledgment of the tremendous contributions of ISC and you yourself Mr. Hankins, I have to comment that failover in isc-dhcp is broken by design because it requires the amount of handholding and operator thinking in the event of a failure that you explained to us at length is required. Failure needs to be handled automatically and without any intervention at all, otherwise you might as well not have it and I think most network operators would agree. I am certainly not prepared to develop proof of concept code or go the full route of developing such a server myself, however, I belive firmly that a failover implementation in dhcp could be designed as a counterpoint to the current implementation that is reliable, simple, scalable and requiring no special procedures once a 'break' occurs. The method used by isc-dhcpd, I think, creates the problem of the potential for unreliable failover because it's not designed for the 'right' problem. But there are example implementations - such as vrrp/carp - that would form the basis of trustworthy dhcp failover protocol. Your key issues are a) broadcast discovery packets, which every listening host on the lan segment (such as 1 or more slaves) can easily respond to, and b) unicast frames from relay agents and others, which could easily be handled by a virtual mac/shared ip address by a group of slaves. This means that redundancy of more than 2 hosts is already possible. The last pieces are protocol for servers to join and leave the pool of hosts serving dhcp, a master election protocol that pre-determines the order of slaves to fail over to in order to avoid the half-brain syndrome, a sanity checking protocol to ensure the elected master is sane and kicking (eg: the slaves all hit the master with, what else, dhcp requests), and a well defined group database update protocol over the network so that leases hit some fixed storage somewhere, sometime. Just my $0.02 worth. Mike- ------------------------------ Message: 2 Date: Fri, 19 Mar 2010 21:30:20 -0400 From: Steve Meuse <smeuse@mara.org> Subject: Re: CRS-3 To: Paul Ferguson <fergdawgster@gmail.com> Cc: "nanog@nanog.org list" <nanog@nanog.org> Message-ID: <20100320013020.GA1574@mara.org> Content-Type: text/plain; charset=us-ascii Paul Ferguson expunged (fergdawgster@gmail.com):
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Anyone have any idea how much a fully configured CRS-3 would cost? Or how much power it would consume? Or how much heat it would generate?
Admittedly, my information on these topics comes from NPR these days. :-)
They said it costs ~US$90k, and that AT&T was in trails.
$90k is the price of the special lift jack you need to move them around :) -Steve ------------------------------ Message: 3 Date: Fri, 19 Mar 2010 22:37:48 -0300 From: jim deleskie <deleskie@gmail.com> Subject: Re: CRS-3 To: Steve Meuse <smeuse@mara.org> Cc: "nanog@nanog.org list" <nanog@nanog.org> Message-ID: <ffcec29f1003191837n5b177b0exbeede90529eefbda@mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1 Thats funny, not sure if Cisco sells one or not but back in the day, I worked @ Avici, and we did in fact have a special jack used to move the chassis around :) -jim On Fri, Mar 19, 2010 at 10:30 PM, Steve Meuse <smeuse@mara.org> wrote:
Paul Ferguson expunged (fergdawgster@gmail.com):
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Anyone have any idea how much a fully configured CRS-3 would cost? ?Or how much power it would consume? ?Or how much heat it would generate?
Admittedly, my information on these topics comes from NPR these days. :-)
They said ?it costs ~US$90k, and that AT&T was in trails.
$90k is the price of the special lift jack you need to move them around :)
-Steve
------------------------------ Message: 4 Date: Sat, 20 Mar 2010 09:43:41 +0100 (CET) From: sthaug@nethelp.no Subject: Re: ISC DHCP server failover To: mike-nanog@tiedyenetworks.com Cc: nanog@nanog.org Message-ID: <20100320.094341.74713325.sthaug@nethelp.no> Content-Type: Text/Plain; charset=us-ascii
With all due respect and acknowledgment of the tremendous contributions of ISC and you yourself Mr. Hankins, I have to comment that failover in isc-dhcp is broken by design because it requires the amount of handholding and operator thinking in the event of a failure that you explained to us at length is required. Failure needs to be handled automatically and without any intervention at all, otherwise you might as well not have it and I think most network operators would agree.
Note that this method of handling failover is inherent in the original DHCP failover design. See http://tools.ietf.org/id/draft-ietf-dhc-failover-12.txt Specifically, quoting from the above draft, "While this technique works in some domains, having the only server to which a DHCP client can communicate voluntarily shut itself down seems like something worth avoiding. The failover protocol will operate correctly while both servers are unable to communicate, whether they are both running or not. At some point there may be resource contention, and if one of the servers is actually down, then the operator can inform the operational server and the operational server will be able to use all of the failed server's resources." I certainly cannot speak for "most network operators". However, I will note that I have been aware of this behavior of the IDC DHCP server as long as I have been running it in failover mode.
I am certainly not prepared to develop proof of concept code or go the full route of developing such a server myself, however, I belive firmly that a failover implementation in dhcp could be designed as a counterpoint to the current implementation that is reliable, simple, scalable and requiring no special procedures once a 'break' occurs.
And which implements failover protocol in the IETF draft? Steinar Haug, Nethelp consulting, sthaug@nethelp.no ------------------------------ Message: 5 Date: Sat, 20 Mar 2010 11:27:44 +0000 (GMT) From: Jess Kitchen <jess.kitchen@adjacentnetworks.net> Subject: Help with a 3561 debug To: nanog@nanog.org Message-ID: <alpine.BSF.2.00.1003201122110.72001@beaujolais.extremis.net> Content-Type: TEXT/PLAIN; format=flowed; charset=US-ASCII Hello, If anyone is single homed via Savvis AS3561 that could spare a minute to help with a couple of mtr/tcptraceroute/iperfs that would be great- trying to drill down a peculiar and intermittent issue that has been occurring since some time Thursday (packets indescriminately dropped on the floor but only on particular paths) Please mail offlist, thanks -- Jess Kitchen <jess.kitchen@adjacentnetworks.net> ------------------------------ _______________________________________________ NANOG mailing list NANOG@nanog.org https://mailman.nanog.org/mailman/listinfo/nanog End of NANOG Digest, Vol 26, Issue 106 **************************************