[Xorp-users] multicast over GRE tunnel

[Pavlin Radoslavov]

Christian Lyra <lyra at pop-pr.rnp.br> wrote:

> Hi there,
> 
> 	I´d like to setup a xorp router to do multicast over a GRE tunnel. My 
> setup is like this:
> 
> [multicast_enabled_net]----[Cisco-Router]---[no-multicast_net]--[xorp_router]---[desktops]
> 
> 	Between Cisco-router and xorp_router there´s a GRE tunnel so I can 
> trasverse the non_multicast_net. The protocol used is PIM-SM and there
> ´s a "static" RP on multicast_enabled_net.
> 
> 	I´m sure that all the other parts are ok, because I had a cisco 2500 in 
> the place of xorp_router and it work just fine with a simple config 
> like this one:
> 
> ip multicast-routing
> interface Tunnel1
>  ip address 200.x.x.154 255.255.255.252
>  ip pim sparse-mode
>  tunnel source 200.y.y.191
>  tunnel destination 200.y.y.9
> 
> ip pim rp-address 200.z.z.z
> ip mroute 0.0.0.0 0.0.0.0 tunnel0
> 
> 	I tried to emulate this same configuration with xorp:
> 
> xorp at teste# show
>     protocols {
>         igmp {
>             interface eth0 {
>                 vif eth0 {
>                     query-interval: 30
>                 }
>             }
>             interface tun0 {
>                 vif tun0 {
>                 }
>             }
>         }
>         pimsm4 {
>             interface "register_vif" {
>                 vif "register_vif" {
>                 }
>             }
>             interface tun0 {
>                 vif tun0 {
>                 }
>             }
>             interface eth0 {
>                 vif eth0 {
>                 }
>             }
>             static-rps {
>                 rp 200.z.z.z {
>                     group-prefix 224.0.0.0/4 {
>                     }
>                 }
>             }
>         }
>         static {
>             route 0.0.0.0/0 {
>                 next-hop: 200.x.x.x
>             }
>             mrib-route 0.0.0.0/0 {
>                 next-hop: 200.x.x.153 /* tunnel */
> }
>         }
>     }
>     fea {
>         unicast-forwarding4 {
>         }
>     }
>     interfaces {
>         interface eth0 {
>             vif eth0 {
>                 address 200.x.x.191 {
>                     prefix-length: 24
>                 }
>             }
>         }
>         interface lo {
>             vif lo {
>             }
>         }
>         interface tun0 {
>             vif tun0 {
>                 address 200.x.x.154 {
>                     prefix-length: 30
>                     multicast-capable: true
>                 }
>             }
>         }
>     }
>     plumbing {
>         mfea4 {
>             interface eth0 {
>                 vif eth0 {
>                 }
>             }
>             interface "register_vif" {
>                 vif "register_vif" {
>                 }
>             }
> 	interface tun0 {
>                 vif tun0 {
>                 }
>             }
>         }
>     }
> 
> 
> 	One thing that I noticed is this:
> xorp at teste> show pim neighbors
> Interface    DRpriority NeighborAddr    V Mode   Holdtime Timeout
> tun0                  1 200.x.x.153   2 Sparse      105      82
> 
> 
> 	But Cisco doesnt see the xorp as a neighbor! (when using the cisco 2500 
> instead of xorp, this Cisco router sees two neighbors, one is the 
> upstream one and the other the 2500).
> 
> bb3#show ip pim neighbor
> PIM Neighbor Table
> Neighbor          Interface                Uptime/Expires    Ver   DR
> Address                                                            
> Prio/Mode
> <wanip>     FastEthernet1/1/0        04:14:05/00:01:39 v2    N /
> 
> 
> 	Maybe I´m missing something.... or this can be compatibility problem 
> between xorp and cisco? Any clues? I can see the PIM join messagens 
> going out from tunnel interface.
> 
> 	Btw... the xorp is running in a debian sarge. Kernel from distro, and a 
> little script to create the tun interface before the xorp_rtmgr is 
> started:
> 
> ip tunnel add tun0 mode gre remote 200.ci.s.co local 200.lo.ca.l dev 
> eth0
> 
> ifconfig tun0 allmulti
> ifconfig tun0 multicast


Your XORP configuration seems right. Well, you don't really need the
"lo" interface configuration, but it shouldn't hurt as long as you
don't touch it (e.g., reconfigure it).

You mentioned that you see PIM Join messages going out from the
tunnel interface. Do you see PIM Hello messages as well?

If yes, could you check whether they have the IP Router Alert option
set. This option shouldn't be set (it was specified in earlier drafts
of the PIM-SM spec, but not anymore), and some (Cisco?) equipment
might not like PIM control packets if the option is set.
XORP-1.3 and earlier had the IP Router Alert option included, but
this has been fixed in the latest XORP code in CVS.
If you are running XORP-1.3 (or earlier), please get the latest code
from anon CVS and see whether you still have the problem.

Regards,
Pavlin

> 
> -- 
> Christian Lyra
> POP-PR - RNP
> 
> http://lyra.soueu.com.br
> 
>   ``The rules of programming are transitory; only Tao is eternal. 
> Therefore you must contemplate Tao before you receive enlightenment.'' 
>   ``But how will I know when I have received enlightenment?'' asked the 
> novice. 
>   ``Your program will then run correctly,'' replied the master. 
> 						The Tao Of Programing
> 
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