Date: Fri, 4 Mar 2011 05:55:38 +0200 From: Eugene Perevyazko <john@dnepro.net> To: freebsd-ipfw@freebsd.org Subject: ipfw fwd and multicast mac address Message-ID: <20110304035538.GA54753@traktor.dnepro.net>
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Hi I've stumbled on a pretty strange issue in combination of ipfw fwd rules with multicast. The system is 7-Stable. It runs ospf, that uses MC groups 224.0.0.5 and 224.0.0.6. Normally those groups use dst mac addresses of 01:00:5e:00:00:05 and 01:00:5e:00:00:06 respectively where last 4 bytes are taken from group's IP. Then I needed to add some fwd rules like this: fwd 192.168.31.14 out xmit em0 (em0 is the interface on which ospf is running) Somehow after that MC dst mac has got 2 bytes changed: 224.0.0.5 got 01:00:5e:a8:1f:05 and 224.0.0.6 got 01:00:5e:a8:1f:06 "a8:1f" clearly is "168.31" from fwd destination. Of course this means no ospf anymore. I've fixed this by adding "pass dst-ip 224.0.0.0/8" before "fwd" but it has made my evening much more lively until I figured what's happening. The question is if this is intended consequence and if yes then why change only two bytes instead of four (irony intended)? -- Eugene Perevyazko
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