North American Network Operators Group

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Re: Another question on rfc1918

  • From: Bruce M Simpson
  • Date: Sat Nov 24 15:59:59 2007

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: