Can anyone provide pointers to an MOSPF implementation for Solaris 2.5
(without full OSPF if possible - I plan static routs) or better yet, a
multicast proxy or Firewall-1 rule that will pass multicast correctly?
An alternative would be a proxy/rule for joining an external group and
then doing NAT to unicast to selected host(s) internally. Anyone got
one they can share?
By running _Mrouted_ on the firewall I can multicast between LAN's on
either side of Firewall-1 on a SUN with Solaris 2.5 (I know... UDP,
multicast <> security, but we have to have it.) Alas, the backbone
(external) router will be running MOSPF. MOSPF and DVMRP supposedly do
not talk to each other on Bay Networks routers (over which I have no
>From what I can tell from some searches, as of June '96 gated did not
support MOSPF. It will someday but it doesn't look like it will be in
time to help me.
Knowledge sharing and misinformation:
Multicast uses the Class D IP addresses to transmit a single packet that
can be seen by a group of hosts. An IGMP (protocol 2, not ICMP) "join"
(or "drop") message is sent to multicast capable routers by hosts that
wish to join a multicast group. The router uses either MOSPF or DVMRP to
tell other routers it has group memebers for that group. When a
multicast UDP packet is sent by one host the routers unicast it between
routers that have group memebers for that packet. When a router has an
attached LAN with memebers in the group it sends that packet out with a
multicast IP address (Ex: 220.127.116.11) on the LAN's multicast MAC
address. (Ethernet actually ends up mapping 4 multicast IP addresses to
each ethernet multicast address.)
The need to write to a multicast MAC address is why I think regular NAT
will not work well with multicast. We could try to work out something by
overloading IP addresses on each interface and forcing a multicast MAC
address on each multicast IP address in the ARP table but with a bunch
of multicast addresses this is a painfully tedious process, if it even
Mrouted takes care of all of that but then the firewall is acting as a
router running DVMRP, which is incompatible with MOSPF (multicast
extensions to OSPF!) I tried running an AltaVista search on +MOSPF +sun
+multicast and got limited results and no pointers to MOSPF code
Adam Safier asafier @
CSC-SED-Infosec (301) 794-1349 (301) 552-3272 (fax)
Curious Cat Question:
How does DIX Ethernet know the packet length?
802.3 Ethernet has a length field but DIX has a type and no length
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