pf.conf and cable modem

[RW]

On Wed, 28 Feb 2007 13:19:13 -0500
alex at schnarff.com wrote:

> Quoting RW <fbsd06 at mlists.homeunix.com>:
> 
> > On Wed, 28 Feb 2007 12:44:21 -0500
> > alex at schnarff.com wrote:

> > I was using a half-bridge modem that had a 30 second lease time,
> > which was definitely renewing. It would also give me a private
> > address when PPPoA went down, and I saw that happen too.
> 
> Are you sure it was a 30 *second* lease time? No sane ISP would set 
> such a low value -- that's a surefire way to overwhelm their DHCP 
> servers.

As I said, it was a half-bridge modem. It terminates PPPoA and delivers
the public IP address and DNS server addresses with its own DHCP
server. When PPP is not connected it issues a private IP address
instead.  

Until the Draytek Vigor 100 offered true PPPoA to PPPoE bridging,
half-bridge modems were the only ethernet-based modems that would work
with FreeBSD and PPPoA.  

> > I added-in some early static rules to log all the DHCP packets.
> > IIRC I never saw any of the lease renewal packets, just some
> > broadcast packets. I asked in this list about it but never got a
> > reply.
> 
> What were the rules? I'd be curious to see them.
>

pass out log  quick on $ext_if proto udp from  port { bootps, bootpc}  to port { bootps, bootpc}
pass in  log  quick on $ext_if proto udp from  port { bootps, bootpc}  to port { bootps, bootpc}

I can't remember the details, but the only packets I saw with tcpdump
were some incoming broadcasts from the DHCP server.