[Bridge] Bridge question

[Bridge] Bridge question

[Hai Wang]

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Hello,

 Do you know why it is impossible to add more than #254 interfaces on a
bridge, why we need such a limit, how it can be exceeded?

  Thanks!

 Regards!

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Re: [Bridge] Bridge question

[Stephen Hemminger]

On Thu, 3 Nov 2005 17:16:45 -0500
Hai Wang <u2.ireland@gmail.com> wrote:

> Hello,
> 
>  Do you know why it is impossible to add more than #254 interfaces on a
> bridge, why we need such a limit, how it can be exceeded?
> 
>   Thanks!
> 
>  Regards!

You can have up 1023 interfaces with 2.6.  I didn't want to change the 2.4
code, only critical bug fixes get backported.

-- 
Stephen Hemminger <shemminger@osdl.org>
OSDL http://developer.osdl.org/~shemminger

Re: [Bridge] Bridge question

[Hai Wang]

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 Stephen,

Did you mean that the #255 limit is set in 2.4 Kernel, not
> bridge-utility? I am wondering why there is such limit,
> performance-related, or...? If I have to modify kernel 2.4 to exceed the
> limit, can you tell me where I should look at? Any drawback if I increase
> the limit up to 6000?
>
> Many thanks
>
>
> From: bridge-bounces@lists.osdl.org
> [mailto:bridge-bounces@lists.osdl.org] On Behalf Of Stephen Hemminger
> Sent: Thursday, November 03, 2005 6:06 PM
> To: Hai Wang
> Cc: bridge@lists.osdl.org
> Subject: Re: [Bridge] Bridge question
>
> On Thu, 3 Nov 2005 17:16:45 -0500
> Hai Wang <u2.ireland@gmail.com> wrote:
>
> > Hello,
> >
> > Do you know why it is impossible to add more than #254 interfaces on
> a
> > bridge, why we need such a limit, how it can be exceeded?
> >
> > Thanks!
> >
> > Regards!
>
> You can have up 1023 interfaces with 2.6. I didn't want to change the
> 2.4
> code, only critical bug fixes get backported.
>
> --
> Stephen Hemminger <shemminger@osdl.org>
> OSDL http://developer.osdl.org/~shemminger
>

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Re: [Bridge] Bridge question

[Stephen Hemminger]

On Thu, 3 Nov 2005 18:17:37 -0500
Hai Wang <u2.ireland@gmail.com> wrote:

>  Stephen,
> 
> Did you mean that the #255 limit is set in 2.4 Kernel, not
> > bridge-utility? I am wondering why there is such limit,
> > performance-related, or...? If I have to modify kernel 2.4 to exceed the
> > limit, can you tell me where I should look at? Any drawback if I increase
> > the limit up to 6000?
> >

Spanning tree protocol has limit on the protocol of 16 bits for port_id.
originally 8 bits were for priority and 8 bits were for port number,
but I added the cheat that vendors were using of using 2 bits of priority
for port number.

-- 
Stephen Hemminger <shemminger@osdl.org>
OSDL http://developer.osdl.org/~shemminger

Re: [Bridge] Bridge question

[Hai Wang]

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 Stephen,
  Can you tell me how you did the trick in code? From what you said that max
of limit only can be 1023, 6000 is not doable, right?

Regards!


On 11/3/05, Hai Wang <hwang@finepoint.com> wrote:
>
> Can you tell me how you did the trick? From what you said that max of
> limit only can be 1028, no more, right?
>
> Regards!
>
> --
> Hai Wang
> Principle Software Engineer
> Fine Point Technologies, Inc.
> 139 Centre Street, 6th Floor
> New York, New York 10013-4408
> email: hwang@finepoint.com
> phone: +1.212.962.7410 x 326
> fax: +1.212.962.7404
> web: http://www.finepoint.com
>
> -----Original Message-----
> From: bridge-bounces@lists.osdl.org
> [mailto:bridge-bounces@lists.osdl.org] On Behalf Of Stephen Hemminger
> Sent: Thursday, November 03, 2005 6:33 PM
> To: Hai Wang
> Cc: bridge@lists.osdl.org
> Subject: Re: [Bridge] Bridge question
>
> On Thu, 3 Nov 2005 18:17:37 -0500
> Hai Wang <u2.ireland@gmail.com> wrote:
>
> > Stephen,
> >
> > Did you mean that the #255 limit is set in 2.4 Kernel, not
> > > bridge-utility? I am wondering why there is such limit,
> > > performance-related, or...? If I have to modify kernel 2.4 to exceed
> the
> > > limit, can you tell me where I should look at? Any drawback if I
> increase
> > > the limit up to 6000?
> > >
>
> Spanning tree protocol has limit on the protocol of 16 bits for port_id.
> originally 8 bits were for priority and 8 bits were for port number,
> but I added the cheat that vendors were using of using 2 bits of
> priority
> for port number.
>
> --
> Stephen Hemminger <shemminger@osdl.org>
> OSDL http://developer.osdl.org/~shemminger
>

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Re: [Bridge] Bridge question

[Ben Greear]

Hai Wang wrote:
> Stephen,
>  
> 
>     Did you mean that the #255 limit is set in 2.4 Kernel, not
>     bridge-utility? I am wondering why there is such limit,
>     performance-related, or...? If I have to modify kernel 2.4 to exceed the
>     limit, can you tell me where I should look at? Any drawback if I
>     increase the limit up to 6000?

So, could you add a bridge group of bridge groups?

Ben

-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com

Re: [Bridge] Bridge question

[Hai Wang]

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Stephen,
  Since your trick is using 2 (even 4) priority bits, do you think it could
cause some cmpatibility issue with other STP implementation which still uses
these bits? (it seems to me that port priority is local significant. maybe
we can use all 8 bits for port ID, can't we?)
  If we take other approaches, like create more than one bridges on one
Linux box, I am not sure if it is feasible, since I saw all bridges created
on the box have the same bridge ID.
  Thanks!


 On 11/3/05, Ben Greear <greearb@candelatech.com> wrote:
>
> Hai Wang wrote:
> > Stephen,
> >
> >
> > Did you mean that the #255 limit is set in 2.4 Kernel, not
> > bridge-utility? I am wondering why there is such limit,
> > performance-related, or...? If I have to modify kernel 2.4 to exceed the
> > limit, can you tell me where I should look at? Any drawback if I
> > increase the limit up to 6000?
>
> So, could you add a bridge group of bridge groups?
>
> Ben
>
> --
> Ben Greear <greearb@candelatech.com>
> Candela Technologies Inc http://www.candelatech.com
>
>

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Re: [Bridge] Bridge question

[Stephen Hemminger]

On Fri, 4 Nov 2005 08:19:35 -0500
Hai Wang <u2.ireland@gmail.com> wrote:

> Stephen,
>   Since your trick is using 2 (even 4) priority bits, do you think it could
> cause some cmpatibility issue with other STP implementation which still uses
> these bits? (it seems to me that port priority is local significant. maybe
> we can use all 8 bits for port ID, can't we?)
>   If we take other approaches, like create more than one bridges on one
> Linux box, I am not sure if it is feasible, since I saw all bridges created
> on the box have the same bridge ID.
>   Thanks!

The port id is treated as a 16 bit ordered field by STP. So the other
side won't have any problem. Nested bridge's won't work for a bunch of
implementation related reasons, it's not impossible to change to allow
that just a lot of work getting rid of all the possible race issues.

The bridge id comes from the Mac of the first interface in bridge.
So if you have mulitple bridges they all would have different bridge ids.


-- 
Stephen Hemminger <shemminger@osdl.org>
OSDL http://developer.osdl.org/~shemminger

Re: [Bridge] Bridge question

[Hai Wang]

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Hello Stephen,
  I was not talking about nested bridges, I meant all bridges created on one
Linux are independent. As matter of fact, brctl does not allow to add a
bridge to another bridge.
  In my case, I have 10 BR2684 interfaces and eth0 on one linux PC with the
same MAC address, nas0....nas9.
  I create two bridges br0 and br1, and add nas0....nas5 and eth0.32 (VLAN)
into br0, and add nas6..nas9 and eth0.33 into br1, as I mentioned above,
nas0...nas9 have the same MAC whereas eth0.32 and eth0.32 also share a MAC,
so br0 and br1 have the same Bridge ID, do you think that the scenario will
work?
  Thanks!
 Regards!
              I am not talking about nested

 On 11/4/05, Stephen Hemminger <shemminger@osdl.org> wrote:
>
> On Fri, 4 Nov 2005 08:19:35 -0500
> Hai Wang <u2.ireland@gmail.com> wrote:
>
> > Stephen,
> > Since your trick is using 2 (even 4) priority bits, do you think it
> could
> > cause some cmpatibility issue with other STP implementation which still
> uses
> > these bits? (it seems to me that port priority is local significant.
> maybe
> > we can use all 8 bits for port ID, can't we?)
> > If we take other approaches, like create more than one bridges on one
> > Linux box, I am not sure if it is feasible, since I saw all bridges
> created
> > on the box have the same bridge ID.
> > Thanks!
>
> The port id is treated as a 16 bit ordered field by STP. So the other
> side won't have any problem. Nested bridge's won't work for a bunch of
> implementation related reasons, it's not impossible to change to allow
> that just a lot of work getting rid of all the possible race issues.
>
> The bridge id comes from the Mac of the first interface in bridge.
> So if you have mulitple bridges they all would have different bridge ids.
>
>
> --
> Stephen Hemminger <shemminger@osdl.org>
> OSDL http://developer.osdl.org/~shemminger
>

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Re: [Bridge] Bridge question

[Hai Wang]

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Hello Stephen,
  I have two questions for you, please help me.
  1. Are you aware that kernel panic issue when brtcl managed to remove
interfaces on the bridge on RH9 (2.4.X)? it is random, it seems to me that
it is racing issue? any fix?
  2. I went through ChangeLog of kernel, I found
 -------------------------------------------------------------------------------------------------

*Summary of changes from v2.6.6 to v2.6.7*

shemminger@osdl.org

      [BRIDGE]: Allow multiple interfaces with same address (necessary
for VLAN's).

-----------------------------------------------------

it seems to me that ethernet bridge allows interfaces with same MACs
address only on kernel 2.6.7 or later, right? If I want to backport
the feature to kernel 2.4.x, what I should take care?



Many thanks

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Re: [Bridge] Bridge question

[Stephen Hemminger]

On Tue, 8 Nov 2005 08:50:28 -0500
Hai Wang <u2.ireland@gmail.com> wrote:

> Hello Stephen,
>   I have two questions for you, please help me.
>   1. Are you aware that kernel panic issue when brtcl managed to remove
> interfaces on the bridge on RH9 (2.4.X)? it is random, it seems to me that
> it is racing issue? any fix?

Try 2.4.X latest first. Redhat kernels were a mix of 2.4 and 2.6.

>   2. I went through ChangeLog of kernel, I found
>  -------------------------------------------------------------------------------------------------
> 
> *Summary of changes from v2.6.6 to v2.6.7*
> 
> shemminger@osdl.org
> 
>       [BRIDGE]: Allow multiple interfaces with same address (necessary
> for VLAN's).
> 
> -----------------------------------------------------
> 
> it seems to me that ethernet bridge allows interfaces with same MACs
> address only on kernel 2.6.7 or later, right? If I want to backport
> the feature to kernel 2.4.x, what I should take care?

I only fix crashes on 2.4

-- 
Stephen Hemminger <shemminger@osdl.org>
OSDL http://developer.osdl.org/~shemminger