The ip and smcroute Multicast Utilities

Linux multicast setup is performed via the ip utility. smcroute(8) is an alternative to ip and to mrouted/pimd, which manipulates Linux kernel multicast routes statically. You can find this utility at http://www.cschill.de/smcroute; it might come in handy in the absence of mrouted/pimd or if you lack IGMP signaling. This utility essentially adds/removes multicast routes and joins/leaves multicast groups. You can start smcroute as a daemon by typing smcroute -d, whereas ip is just a powerful vehicle to manipulate the kernel multicast settings. Example 14-12 offers an example of joining a multicast group via smcroute as well as adding a static multicast routing entry. Example 14-13 summarizes the multicast command section of the Linux ip utility.

Example 14-12. smcroute Utility

[root@callisto:~#] smcroute -h

usage: smcroute [-v] [-d]

           [-a     [] ...]

               [-r   ]

               [-j  ]

               [-l  ]



[root@callisto:~#] smcroute –d



[root@callisto:~#] smcroute  -j eth1 224.7.7.7



[root@callisto:~#] smcroute  -a eth1 182.168.2.254 224.4.4.4 eth0



[root@callisto:~#] netstat -g

IPv6/IPv4 Group Memberships

Interface       RefCnt Group

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

lo              1      ALL-SYSTEMS.MCAST.NET

eth0            1      ALL-SYSTEMS.MCAST.NET

eth1            1      224.7.7.7

eth1            1      224.2.2.2

eth1            1      NTP.MCAST.NET

eth1            1      ALL-SYSTEMS.MCAST.NET



[root@callisto:~#] ip mroute show

(182.168.2.254, 224.4.4.4)       Iif: eth1       Oifs: eth0

(192.168.1.1, 224.2.2.2)         Iif: unresolved

(192.168.2.7, 224.2.2.2)         Iif: unresolved

NOTE

Only one multicast router daemon can be active at any time. It is impossible to run smcroute and mrouted or pimd simultaneously.

Example 14-13. Multicast Commands of the ip Utility

[root@callisto:~#] ip mroute help

Usage: ip mroute show [ PREFIX ] [ from PREFIX ] [ iif DEVICE ]



[root@callisto:~#] ip maddr help

Usage: ip maddr [ add | del ] MULTIADDR dev STRING

      ip maddr show [ dev STRING ]



[root@callisto:~#] ip -s mroute

(192.168.2.7, 224.2.2.2)         Iif: eth1

 4169 packets, 621166 bytes

(192.168.1.1, 224.2.2.2)         Iif: eth1

 6302 packets, 2012324 bytes

(192.168.1.1, 224.0.1.1)         Iif: eth1

 315 packets, 10184 bytes



[root@callisto:~#] ip -s maddr

1:      lo

       inet  224.0.0.1

2:      eth0

       link  01:00:5e:00:00:02

       link  01:00:5e:00:00:04

       link  01:00:5e:00:00:01

       inet  224.0.0.2

       inet  224.0.0.4

       inet  224.0.0.1

3:      eth1

       link  01:00:5e:02:02:02

       link  01:00:5e:00:01:01

       link  01:00:5e:00:00:02

       link  01:00:5e:00:00:04

       link  01:00:5e:00:00:01

       inet  224.2.2.2

       inet  224.0.1.1

       inet  224.0.0.2

       inet  224.0.0.4

       inet  224.0.0.1

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