2.6 kernel: Cannot make multiple dummy network interfaces

2.6 kernel: Cannot make multiple dummy network interfaces

[Mike Schmidt]

[-- Attachment #1: Type: text/plain, Size: 3028 bytes --]



(please cc me directly with any responses - I am not (yet) a member of 
this mailing list.

*2.6 kernel: Cannot make multiple dummy network interfaces*
------------------------------------------------------------------------
I'm trying to set up a number of dummy interfaces but FC6 (Centos4, even 
RHEL4) won't make more than 1. a modprobe -c lists two default dummy 
interfaces, dumm0 and dummy1, just as it did even back to rh8. On my 
rh8/rh9 systems, there is no problem, I can generate as many dummy n as 
I want by adding alias and options lines in modules.conf. On 
FC6/Centos/RHEL (I assume as of kernel 2.6, but I don't have any early 
FC systems running) I can only create 1 dummy. I am trying to build a 
network simulator for testing purposes - a bridge with 100+ network 
interfaces. They have to be dummy (not just an alias) because they need 
separate MAC addresses.  I have tried the same thing on Knoppix, running 
2.6.17, with the same results. Centos4 and RHEL4 use kernel 2.6.9

On FC6: (kernel 2.6.20)
 >modprobe -c | grep dummy:
alias dummy0 dummy
alias dummy1 dummy
install dummy0 /sbin/modprobe -o dummy0 --ignore-install dummy
install dummy1 /sbin/modprobe -o dummy1 --ignore-install dummy

 >ip link
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast 
qlen 1000
link/ether 00:18:8b:e6:c3:82 brd ff:ff:ff:ff:ff:ff
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast 
qlen 1000
link/ether 00:0e:2e:b1:20:e6 brd ff:ff:ff:ff:ff:ff

 >modprobe dummy0
 >modprobe dummy1

 >ip link
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast 
qlen 1000
link/ether 00:18:8b:e6:c3:82 brd ff:ff:ff:ff:ff:ff
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast 
qlen 1000
link/ether 00:0e:2e:b1:20:e6 brd ff:ff:ff:ff:ff:ff
4: dummy0: <BROADCAST,NOARP> mtu 1500 qdisc noop
link/ether aa:96:c7:d9:40:eb brd ff:ff:ff:ff:ff:ff

This same thing give me two dummy interfaces in rh8. I have no 
difficulty making 100 or more dummy interfaces in rh8. (running 2.4.31). 
Note that I have not made any changes to the modprobe configuration 
here. Normally I would have at least 100 aliases - dummy0-dummy99.

On all 2.6 kernels I have checked, the kernel config has CONFIG_DUMMY=m. 
However, the modprobe configuration for 2.4 kernels is different (uses 
option instead of install statements in modules.conf).
Is there something going on that prevents me from loading multiple 
copies of the dummy driver? Is there anything I can do about this?

Thanks very much. There is very little information about this kind of 
thing available. I'm afraid I'm stuck between a rock and a hard place - 
I need 2.6 for some new device drivers not available in 2.4, and I need 
2.54 for my dummy net devices....

Again, I thank anyone who can help me.

Mike


[-- Attachment #2: mike.vcf --]
[-- Type: text/x-vcard, Size: 354 bytes --]

begin:vcard
fn:Mike Schmidt
n:Schmidt;Mike
org:Intello Technologies Inc. 
adr;quoted-printable;quoted-printable:;;580 1=C3=A8re Rue;Saint-Jean-sur-Richelieu;Qu=C3=A9;J2X 3B4;Canada
email;internet:mike@intello.com
title:Vice-President
tel;work:450-358-2266 x223
tel;cell:514-835-9497
x-mozilla-html:FALSE
url:http://www.intello.com
version:2.1
end:vcard

Re: 2.6 kernel: Cannot make multiple dummy network interfaces

[Lennart Sorensen]

On Fri, Jun 08, 2007 at 01:34:16PM -0400, Mike Schmidt wrote:
> (please cc me directly with any responses - I am not (yet) a member of 
> this mailing list.
> 
> *2.6 kernel: Cannot make multiple dummy network interfaces*
> ------------------------------------------------------------------------
> I'm trying to set up a number of dummy interfaces but FC6 (Centos4, even 
> RHEL4) won't make more than 1. a modprobe -c lists two default dummy 
> interfaces, dumm0 and dummy1, just as it did even back to rh8. On my 
> rh8/rh9 systems, there is no problem, I can generate as many dummy n as 
> I want by adding alias and options lines in modules.conf. On 
> FC6/Centos/RHEL (I assume as of kernel 2.6, but I don't have any early 
> FC systems running) I can only create 1 dummy. I am trying to build a 
> network simulator for testing purposes - a bridge with 100+ network 
> interfaces. They have to be dummy (not just an alias) because they need 
> separate MAC addresses.  I have tried the same thing on Knoppix, running 
> 2.6.17, with the same results. Centos4 and RHEL4 use kernel 2.6.9

# modinfo dummy
filename:       /lib/modules/2.6.18-4-gx1/kernel/drivers/net/dummy.ko
license:        GPL
vermagic:       2.6.18-4-gx1 preempt mod_unload GEODEGX1 gcc-3.3
depends:
parm:           numdummies:Number of dummy pseudo devices (int)

Perhaps you want to pass that numdummies aregument with some value.  The
default may be pretty low.

--
Len Sorensen

Re: 2.6 kernel: Cannot make multiple dummy network interfaces

[Mike Schmidt]

[-- Attachment #1: Type: text/plain, Size: 831 bytes --]

Oh, yes! Thank you. The one thing I didn't check - since dummy had no 
parameters in 2.4 kernels, it didn't occur to me to do a modinfo. I just 
did a modprobe dummy0 numdummies=99 and there we are - 99 devices. Thank 
you. I will pass this info on. I searched high and lo through user 
groups and mailing lists, but dummy is such a common word that it is 
difficult to narrow down the search.
Thank you again.

Mike

Lennart Sorensen wrote:
> # modinfo dummy
> filename:       /lib/modules/2.6.18-4-gx1/kernel/drivers/net/dummy.ko
> license:        GPL
> vermagic:       2.6.18-4-gx1 preempt mod_unload GEODEGX1 gcc-3.3
> depends:
> parm:           numdummies:Number of dummy pseudo devices (int)
>
> Perhaps you want to pass that numdummies aregument with some value.  The
> default may be pretty low.
>
> --
> Len Sorensen
>   

[-- Attachment #2: mike.vcf --]
[-- Type: text/x-vcard, Size: 354 bytes --]

begin:vcard
fn:Mike Schmidt
n:Schmidt;Mike
org:Intello Technologies Inc. 
adr;quoted-printable;quoted-printable:;;580 1=C3=A8re Rue;Saint-Jean-sur-Richelieu;Qu=C3=A9;J2X 3B4;Canada
email;internet:mike@intello.com
title:Vice-President
tel;work:450-358-2266 x223
tel;cell:514-835-9497
x-mozilla-html:FALSE
url:http://www.intello.com
version:2.1
end:vcard