[Xorp-users] Linux 2.6 multicast issue using PIM

Chris Robson crobson@cmf.nrl.navy.mil
Mon, 23 Aug 2004 16:58:33 -0400

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Sorry, I thought I said, all my linux boxes where directly connected to 
each other.  But anyway, you have asked for info whcih will take me a few 
days to collect, which I already have started doing, namely, updating all 
boxes in the cofnigure with the latest Fedora Core 2 updates (which 
includes a kernel update) and I did a CVS pull and rebuild.  One question 
however, when I do "make check" on the XORP build, it fails one of the 
tests (I'll have to get that info to you later), should I focus on making 
sure it passes all tests, or not worry about the check test.  Again the 
test config is .......

Host<---->Linux RTR<--->Linux RTR<--->Linux RTR<--->host

All RTRs are directly connected to each other, hosts will actually be 
connected to associated Linux RTR via a Linksys 
hub.  I.E.   Host<-->Linksys Hub<-->Linux RTR.  But the Linux RTR links are 
"not" thru the hub but RTR to RTR direct.

I'll need about a week to complete this, unfortunately I have a job that is 
getting in the way of fun stuff......

Well, U have ask me to collect some info so off I go.....

Thanks again for all the help........l8r....chris

At 01:05 PM 8/23/2004, Pavlin Radoslavov wrote:

> > Bruce
> > Thanks for the comment and this is why the local concern here is the 
> kernel
> > multicast functions are not really working in Linux 2.6, therefore, any
> > user apps (aka PIM) wont function correctly.
> >
> > ...chris
>Based on my test results with a 2.6 kernel, I had no problems with
>multicast forwarding, therefore to solve the problem faster I
>would recommend that we try to isolate it by first looking somewhere
>Hence, can you do the following:
>1. Make sure that you have the following options in you Linux-2.6
>kernel configuration file:
>[those options are mentioned in xorp/pim/README]
>If you don't have the above options enabled, the results are
>2. For consistency, please get the lastest XORP code from the
>    anonymous CVS repository.
>3. Please answer my earlier question whether your PIM routers are
>    directly connected to each other (e.g., via a physical LAN), or
>    whether there is something between them. For example, do you have
>    switches, do you use some tunnels (e.g., openvpn), etc.
>4. Once you start XORP PIM on two neighbor routers, please run
>    tcpdump on the neighboring interfaces on each router. E.g., in
>    your topology you have:
>Host <--> Core 2 (acting as edge router) <--> Core 2 (acting as backbone
>rtr) <--> Core 2 (edge rtr) <--> Host.
>    In that case, please run tcpdump on the interface that connects
>    the first edge router to the backbone router, and on the
>    corresponding interface of the backbone router.
>    In your previous email you said that each router is sending PIM
>    Hello messages, but those messages are not received by the other
>    routers. Hence, by running tcpdump can you confirm whether the
>    PIM Hello messages originated by the backbone router reach the
>    first edge router (and vice-versa). If tcpdump on the backbone
>    router shows that the Hello messages are sent on that interface,
>    but tcpdump on the first edge router does not see those Hello
>    messages, then the Hellos have been lost somewhere between the
>    routers (e.g., a switch in the middle may have filtered them, a
>    virtual tunnel may have been misconfigured, etc). If tcpdump on
>    the receiving side does see the Hellos, but PIM userland daemon
>    doesn't see them, then the problem is within the router itself,
>    and we can take additional steps to find it.
>Once we have the above information, we can trace the problem
>further. Otherwise, we will be just guessing...
> >
> > At 08:21 AM 8/23/2004, Bruce M Simpson wrote:
> >
> > >On Mon, Aug 23, 2004 at 02:04:14PM +0200, Arnaud Le Taillanter wrote:
> > > > Just out of curiosity, why is PIM kernel support necessary for the Xorp
> > > > PIM daemon to operate?
> > > > I've successfully run XORP PIM on a FreeBSD box, I followed the
> > > > documentation and enabled the kernel options MROUTING (fair :) and also
> > > > PIM, but I don't see why Xorp PIM would need PIM support from the
> > > > kernel. Xorp BGP doesn't need BGP support from the kernel for example.
> > >
> > >BGP lives entirely in userland; it only requires specific kernel support
> > >in special circumstances (TCP-MD5).
> > >
> > >PIM does not live entirely in userland. Multicast forwarding functions are
> > >located within the kernel.
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