Two interfaces one subnet (summary)

> > Anyone else want to unconfused Ben? I obviously cannot. The numerous misconceptions propagated in this thread prompted me to go through the relevant sections of RFC 1122 and write a short article on multihomed IP host issues. http://wiki.nil.com/Multihomed_IP_hosts Your contributions, eithe

Re: two interfaces one subnet

> use separate subnets for the different > interfaces. As someone said before, it's not rocket science. It can be a barrier to selling gear if you don't have multiple subnets easily available to you - which is a very big deal for vendors doing evals or for development teams doing staging. Almost

Re: two interfaces one subnet

On Mon, May 11, 2009 at 2:59 PM, Chris Meidinger wrote: > Just to restate here, for people who have been responding both publicly and > privately: > > I know that *I* can make it work, and I know that *you* can make it work. > But I also know that it's not likely to stay working. You might like

Re: two interfaces one subnet

Completely off topic but, does this subject make anyone else immediately think of 2girls1cup? I blame the internets for my making this correlation... --Original Message-- From: Martin Hannigan To: Patrick W. Gilmore Cc: NANOG list Subject: Re: two interfaces one subnet Sent: May 12, 2009

Re: two interfaces one subnet

On 12.05.2009, at 19:37, Curtis Maurand wrote: Try this: http://www.linuxfoundation.org/en/Net:Bridge Wow. It's really hard to convince people that you're not trying to solve a problem today but to avoid one tomorrow. Stil, I want to thank everyone that responded - both publicly and pr

Re: two interfaces one subnet

Try this: http://www.linuxfoundation.org/en/Net:Bridge --Curtis Patrick W. Gilmore wrote: On May 11, 2009, at 5:40 PM, Ben Scott wrote: On Mon, May 11, 2009 at 5:28 PM, Hector Herrera wrote: On Mon, May 11, 2009 at 2:22 PM, David Devereaux-Weber wrote: ... both> interfaces are on the same

Re: two interfaces one subnet

On Tue, May 12, 2009 at 12:12 AM, Patrick W. Gilmore wrote: > On May 11, 2009, at 11:43 PM, Ben Scott wrote: > >> On Mon, May 11, 2009 at 11:01 PM, Patrick W. Gilmore >> wrote: >> > > Do you even read your own posts? Specifically: >>> >>> On May 11, 2009, at 5:40 PM, Ben Scott wrote: >>> >>> E

Re: two interfaces one subnet

On May 11, 2009, at 4:48 PM, Duane Waddle wrote: On Mon, May 11, 2009 at 3:39 PM, Mikael Abrahamsson wrote: IIRC, you can turn the feature off WHEN it makes an issue. Fixed that for you. S550 attached to a 6509, Dell blade in a blade chassis with Power connect switches cross-connected

Re: two interfaces one subnet

David Devereaux-Weber wrote: > > I work with iHDTV , a project that sends uncompressed high > definition television (1.5 Gbps) as UDP over two 1 Gbps interfaces. If both > interfaces are on the same subnet, the OS sees the same router (gateway) > address on both interfaces, and

Re: two interfaces one subnet

On May 11, 2009, at 11:43 PM, Ben Scott wrote: On Mon, May 11, 2009 at 11:01 PM, Patrick W. Gilmore > wrote: Do you even read your own posts? Specifically: On May 11, 2009, at 5:40 PM, Ben Scott wrote: Either way, if the packet *from* X was addressed *to* B but the response comes back from

Re: two interfaces one subnet

On Mon, May 11, 2009 at 11:01 PM, Patrick W. Gilmore wrote: >>> It doesn't matter which physical interface transmits the packet. >> >>  Well, in the general sense, I suppose not.  The computer can put >> whatever it wants in an Ethernet frame, and as long as it's valid for >> the receiving system,

Re: two interfaces one subnet

On May 11, 2009, at 8:04 PM, Ben Scott wrote: On Mon, May 11, 2009 at 6:01 PM, Patrick W. Gilmore wrote: It doesn't matter which physical interface transmits the packet. Well, in the general sense, I suppose not. The computer can put whatever it wants in an Ethernet frame, and as long as

RE: two interfaces one subnet

king" land, as, at the very least, emperical evidence has a quite different story to say. - S -Original Message- From: Chris Adams Sent: Monday, May 11, 2009 16:29 To: nanog@nanog.org Subject: Re: two interfaces one subnet Once upon a time, Kevin Oberman said: > > From: Chr

Re: two interfaces one subnet

Once upon a time, David Coulson said: > Remember, Linux has no concept of downing an interface when the link > goes away Not true in several different ways. You can run netplugd or Network Manager to control it. -- Chris Adams Systems and Network Administrator - HiWAAY Internet Services I do

Re: two interfaces one subnet

Remember, Linux has no concept of downing an interface when the link goes away, so even if you have two interfaces with the same subnet config, the kernel will continue to send traffic to a disconnected interface. Utilizing the bonding kernel module is the only really effective way to handle la

Re: two interfaces one subnet

On Mon, May 11, 2009 at 7:04 PM, Ben Scott wrote: > On Mon, May 11, 2009 at 6:01 PM, Patrick W. Gilmore wrote: >[snip] Many OSes should handle it correctly, in principle, there's nothing wrong with hosts homed twice to the same network and addressed inside the same subnet, but for Linux hosts,

Re: two interfaces one subnet

On Mon, May 11, 2009 at 6:01 PM, Patrick W. Gilmore wrote: > You are assuming facts not in evidence. I *have* actually done this before, so I'd like to think, for my own purposes at least, my experiences are factual. :) > It doesn't matter which physical interface transmits the packet. Wel

Re: two interfaces one subnet

> Date: Mon, 11 May 2009 18:29:08 -0500 > From: Chris Adams > > Once upon a time, Kevin Oberman said: > > > From: Chris Meidinger > > > For example, eth0 is 10.0.0.1/24 and eth1 is 10.0.0.2/24, nothing like > > > bonding going on. The customers usually have the idea of running one > > > int

Re: two interfaces one subnet

Once upon a time, Kevin Oberman said: > > From: Chris Meidinger > > For example, eth0 is 10.0.0.1/24 and eth1 is 10.0.0.2/24, nothing like > > bonding going on. The customers usually have the idea of running one > > interface for administration and another for production (which is a > > _go

Re: two interfaces one subnet

On May 11, 2009, at 6:35 PM, Arnold Nipper wrote: On 12.05.2009 00:25 Patrick W. Gilmore wrote On May 11, 2009, at 6:13 PM, Arnold Nipper wrote: On 11.05.2009 23:47 Patrick W. Gilmore wrote On May 11, 2009, at 5:19 PM, Alex H. Ryu wrote: It may be allowed from host-level, but from router equ

Re: two interfaces one subnet

On 12.05.2009 00:25 Patrick W. Gilmore wrote > On May 11, 2009, at 6:13 PM, Arnold Nipper wrote: >> On 11.05.2009 23:47 Patrick W. Gilmore wrote >>> On May 11, 2009, at 5:19 PM, Alex H. Ryu wrote: >>> It may be allowed from host-level, but from router equipment, I don't think it w

RE: two interfaces one subnet

ferent source IP on the reply. Most firewalls will reject packets such as this. -Original Message- From: Chris Meidinger [mailto:cmeidin...@sendmail.com] Sent: Monday, May 11, 2009 1:29 PM To: nanog@nanog.org Subject: two interfaces one subnet Hi, This is a pretty moronic question, but I

Re: two interfaces one subnet

On May 11, 2009, at 6:13 PM, Arnold Nipper wrote: On 11.05.2009 23:47 Patrick W. Gilmore wrote On May 11, 2009, at 5:19 PM, Alex H. Ryu wrote: It may be allowed from host-level, but from router equipment, I don't think it was allowed at all. Ever used HSRP / VRRP? Two interfaces in the sa

Re: two interfaces one subnet

On May 11, 2009, at 5:59 PM, Chris Meidinger wrote: Just to restate here, for people who have been responding both publicly and privately: I know that *I* can make it work, and I know that *you* can make it work. But I also know that it's not likely to stay working. One day, down the road

Re: two interfaces one subnet

On 11.05.2009 23:47 Patrick W. Gilmore wrote > On May 11, 2009, at 5:19 PM, Alex H. Ryu wrote: > >> It may be allowed from host-level, but from router equipment, I don't >> think it was allowed at all. > > Ever used HSRP / VRRP? Two interfaces in the same subnet. Works > fine. In fact, most

Re: two interfaces one subnet

On 12/05/2009, at 9:00 AM, Charles Wyble wrote: What does two interfaces in one subnet mean? Two NICs? Or virtual interfaces? Also, what does one subnet mean? A. Using the same IP prefix on two different networks (ie. ethernet broadcast domains) with an interface in to each, or B. running

Re: two interfaces one subnet

In my case, each Ethernet interface has its own unique MAC address. Dave On Mon, May 11, 2009 at 4:28 PM, Hector Herrera wrote: > On Mon, May 11, 2009 at 2:22 PM, David Devereaux-Weber > wrote: > > Chris, > > > > I work with iHDTV , a project that sends uncompressed > high > >

Re: two interfaces one subnet

On May 11, 2009, at 5:40 PM, Ben Scott wrote: On Mon, May 11, 2009 at 5:28 PM, Hector Herrera > wrote: On Mon, May 11, 2009 at 2:22 PM, David Devereaux-Weber wrote: ... both> interfaces are on the same subnet, the OS sees the same router (gateway) address on both interfaces, and the results ar

Re: two interfaces one subnet - SOLVED

On 11.05.2009, at 23:39, Mike O'Connor wrote: :Hi, : :This is a pretty moronic question, but I've been searching RFC's on- :and-off for a couple of weeks and can't find an answer. So I'm hoping :someone here will know it offhand. : :I've been looking through RFC's trying to find a clear statemen

Re: two interfaces one subnet

On 11.05.2009, at 23:48, Ben Scott wrote: On Mon, May 11, 2009 at 5:38 PM, Chris Meidinger wrote: For example, eth0 is 10.0.0.1/24 and eth1 is 10.0.0.2/24, nothing like bonding going on. The customers usually have the idea of running one interface for administration and another for productio

Re: two interfaces one subnet

On 5/11/09 3:23 PM, Chris Meidinger wrote: On 11.05.2009, at 23:19, Alex H. Ryu wrote: Unless you configure Layer 2 for two interfaces, it's not going to work. It is invalid from networking principle. If you have to send the traffic for host in same subnet you configured, which interface it sho

Re: two interfaces one subnet

On May 11, 2009, at 4:45 PM, Chris Meidinger wrote: On 11.05.2009, at 22:34, Patrick W. Gilmore wrote: On May 11, 2009, at 4:29 PM, Chris Meidinger wrote: I would be grateful for a pointer to such an RFC statement, assuming it exists. Why would an RFC prohibit this? Most _implementations_

RE: two interfaces one subnet

empla Healthcare (303) 467-4671 matlo...@exempla.org -Original Message- From: Chris Meidinger [mailto:cmeidin...@sendmail.com] Sent: Monday, May 11, 2009 3:39 PM To: Dan White Cc: nanog@nanog.org Subject: Re: two interfaces one subnet On 11.05.2009, at 23:31, Dan White wrote: > Chris Meiding

Re: two interfaces one subnet

> From: Chris Meidinger > Date: Mon, 11 May 2009 23:38:30 +0200 > > On 11.05.2009, at 23:31, Dan White wrote: > > > Chris Meidinger wrote: > >> Hi, > >> > >> This is a pretty moronic question, but I've been searching RFC's on- > >> and-off for a couple of weeks and can't find an answer. So I'm

Re: two interfaces one subnet

On 11.05.2009, at 23:42, Kevin Oberman wrote: Date: Mon, 11 May 2009 16:19:56 -0500 From: "Alex H. Ryu" Unless you configure Layer 2 for two interfaces, it's not going to work. It is invalid from networking principle. If you have to send the traffic for host in same subnet you configured,

Re: two interfaces one subnet

:Hi, : :This is a pretty moronic question, but I've been searching RFC's on- :and-off for a couple of weeks and can't find an answer. So I'm hoping :someone here will know it offhand. : :I've been looking through RFC's trying to find a clear statement that :having two interfaces in the same su

Re: two interfaces one subnet

On Mon, May 11, 2009 at 5:38 PM, Chris Meidinger wrote: > For example, eth0 is 10.0.0.1/24 and eth1 is 10.0.0.2/24, nothing like > bonding going on. The customers usually have the idea of running one > interface for administration and another for production (which is a _good_ > idea) but they want

Re: two interfaces one subnet

On May 11, 2009, at 5:19 PM, Alex H. Ryu wrote: Unless you configure Layer 2 for two interfaces, it's not going to work. It can work. Of course it _may_ not, depending upon your implementation, but then some implementations can't get a single interface to work properly per subnet. It

RE: two interfaces one subnet

Hi Chris, I remember this. I remember it in an early IP RFC, but couldn't find it in 10 minutes of searching. It had to do with intefaces cannot have overlapping address space. One of the IETF greybeards ought to know. It's been a while since I was writing code with marked up rfc's in fro

Re: two interfaces one subnet

> Date: Mon, 11 May 2009 16:19:56 -0500 > From: "Alex H. Ryu" > > Unless you configure Layer 2 for two interfaces, it's not going to work. > It is invalid from networking principle. > If you have to send the traffic for host in same subnet you configured, > which interface it should send out ? >

Re: two interfaces one subnet

On Mon, May 11, 2009 at 5:28 PM, Hector Herrera wrote: > On Mon, May 11, 2009 at 2:22 PM, David Devereaux-Weber > wrote: >> ... both> interfaces are on the same subnet, the OS sees the same router >> (gateway) >> address on both interfaces, and the results are sub-optimal ... around 50% >> packe

Re: two interfaces one subnet

On 11.05.2009, at 23:31, Dan White wrote: Chris Meidinger wrote: Hi, This is a pretty moronic question, but I've been searching RFC's on- and-off for a couple of weeks and can't find an answer. So I'm hoping someone here will know it offhand. I've been looking through RFC's trying to find a

Re: two interfaces one subnet

Chris Meidinger wrote: Hi, This is a pretty moronic question, but I've been searching RFC's on-and-off for a couple of weeks and can't find an answer. So I'm hoping someone here will know it offhand. I've been looking through RFC's trying to find a clear statement that having two interfaces i

Re: two interfaces one subnet

On Mon, May 11, 2009 at 2:22 PM, David Devereaux-Weber wrote: > Chris, > > I work with iHDTV , a project that sends uncompressed high > definition television (1.5 Gbps) as UDP over two 1 Gbps interfaces.  If both > interfaces are on the same subnet, the OS sees the same router (g

Re: two interfaces one subnet

On 11.05.2009, at 23:19, Alex H. Ryu wrote: Unless you configure Layer 2 for two interfaces, it's not going to work. It is invalid from networking principle. If you have to send the traffic for host in same subnet you configured, which interface it should send out ? Basically it may create

Re: two interfaces one subnet

Chris, I work with iHDTV , a project that sends uncompressed high definition television (1.5 Gbps) as UDP over two 1 Gbps interfaces. If both interfaces are on the same subnet, the OS sees the same router (gateway) address on both interfaces, and the results are sub-optimal ...

Re: two interfaces one subnet

Unless you configure Layer 2 for two interfaces, it's not going to work. It is invalid from networking principle. If you have to send the traffic for host in same subnet you configured, which interface it should send out ? Basically it may create broadcast storm loop by putting two ip addresses in

Re: two interfaces one subnet

On 11.05.2009, at 23:00, Charles Wyble wrote: What does two interfaces in one subnet mean? Two NICs? Or virtual interfaces? Two NICs, as in physical interfaces.

Re: two interfaces one subnet

What does two interfaces in one subnet mean? Two NICs? Or virtual interfaces? Mikael Abrahamsson wrote: On Mon, 11 May 2009, Chris Meidinger wrote: I've been looking through RFC's trying to find a clear statement that having two interfaces in the same subnet does not work, but can't find i

Re: two interfaces one subnet

On Mon, May 11, 2009 at 3:39 PM, Mikael Abrahamsson wrote: > ... There are "legitimate" cases where you might want to do > this. > NetApp filers consider this to be a legitimate configuration, even a "supported and recommended one". If I understand the documentation correctly, NetApp will (some

Re: two interfaces one subnet

On 11.05.2009, at 22:34, Patrick W. Gilmore wrote: On May 11, 2009, at 4:29 PM, Chris Meidinger wrote: I would be grateful for a pointer to such an RFC statement, assuming it exists. Why would an RFC prohibit this? Most _implementations_ do, but as far as network "rules" in general it is

Re: two interfaces one subnet

On Mon, 11 May 2009, Chris Meidinger wrote: I've been looking through RFC's trying to find a clear statement that having two interfaces in the same subnet does not work, but can't find it that statement anywhere. I don't know if it still works, but it did in Linux little over 10 years back.

Re: two interfaces one subnet

On May 11, 2009, at 4:29 PM, Chris Meidinger wrote: This is a pretty moronic question, but I've been searching RFC's on- and-off for a couple of weeks and can't find an answer. So I'm hoping someone here will know it offhand. I've been looking through RFC's trying to find a clear statement

two interfaces one subnet

Hi, This is a pretty moronic question, but I've been searching RFC's on- and-off for a couple of weeks and can't find an answer. So I'm hoping someone here will know it offhand. I've been looking through RFC's trying to find a clear statement that having two interfaces in the same subnet d