multicast not happy ?

Poul-Henning Kamp phk at phk.freebsd.dk
Fri Jun 15 21:09:26 UTC 2007


I set up a really simple network here, two boxes with two 
cross-over ethernets:

        10.1.0.1/24 ------------- 10.1.0.2/24
     A						B
        10.2.0.1/24 ------------- 10.2.0.2/24

Ipforwarding is enabled on both, and "routed" is running with
/etc/gateways containing:

	ripv2
	no_solicit
	no_rdisc_adv

And nothing happens at all...

routed in both ends complain about:

	routed: Send mcast sendto(sis2, 224.0.0.9.520): Network is unreachable
	routed: Send mcast sendto(sis1, 224.0.0.9.520): Network is unreachable

Running a tcpdump on one end, the IGMP reports to the new MCast are
sent:

    syv# tcpdump -i vr1 -n -s 2000 -v
    tcpdump: listening on vr1, link-type EN10MB (Ethernet),
	capture size 2000 bytes
    20:35:24.738693 IP (tos 0x0, ttl   1, id 11501, offset 0,
	flags [none], proto: IGMP (2), length: 32, options ( RA
	(148) len 4 )) 10.1.0.1 > 224.0.0.9:
	igmp v2 report 224.0.0.9

    20:35:25.118284 IP (tos 0x0, ttl   1, id 118, offset 0,
	flags [none], proto: IGMP (2), length: 32, options ( RA
	(148) len 4 )) 10.1.0.2 > 224.0.0.9: igmp v2 report 224.0.0.9

But no further trafic is sent.

Netstat -ian shows the mcast groups joined:

vr1    1500 <Link#2>      00:00:24:08:62:ed       25     0        8     0     0
                          01:00:5e:00:00:09       23              7
                          01:00:5e:00:00:01       23              7
vr1    1500 10.1.0.0/24   10.1.0.1                17     -        7     -     -
                          224.0.0.9        
                          224.0.0.1        
vr2    1500 <Link#3>      00:00:24:08:62:ee       28     0        9     0     0
                          01:00:5e:00:00:09       26              7
                          01:00:5e:00:00:01       26              7
vr2    1500 10.2.0.0/24   10.2.0.1                17     -        7     -     -
                          224.0.0.9        
                          224.0.0.1        

as does ifmcstat:
vr1:
        inet 10.1.0.1
                group 224.0.0.9
                        igmpv2
                        mcast-macaddr 01:00:5e:00:00:09 refcnt 1
                group 224.0.0.1
                        mcast-macaddr 01:00:5e:00:00:01 refcnt 1
vr2:
        inet 10.2.0.1
                group 224.0.0.9
                        igmpv2
                        mcast-macaddr 01:00:5e:00:00:09 refcnt 1
                group 224.0.0.1
                        mcast-macaddr 01:00:5e:00:00:01 refcnt 1

Any ideas ?

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.


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