Michael Painter wrote:
Source route allows the packets to follow a set path. It does not require the standard routing protocols and is thus dangerous. Source routing is used in a number of multicast protocols (still) and many are loath to disable it.
Not true. DVMRP with tunnels hasn't been used for inter-domain multicast for a long time. Many implementations, including FreeBSD, have deprecated the use of IPIP and LSRR. I believe most folk who are serious about inter-domain multicast are running BGP with PIM-SM and MSDP. However, this hasn't really been accessible to the individual hobbyist until now, and there are no free MSDP implementations out there that I know of. If security is a concern, turn LSRR off on packet filtering NAT gateways, if you don't know *for sure* that the forwarding plane is smart enough to block LSRR according to a well-defined site security policy. There are however cogent arguments for turning LSRR on in an AS's transit routers here: http://www.gweep.net/~crimson/network/lsrr.html regards, BMS