Re: Problem setting up poptop on RHEL5

On Wed, Aug 31, 2011 at 04:44:05PM +1000, Steve Phillips wrote:
> [root@wibble ppp]# tcpdump -i eth0:3 -n proto 47
> tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
> listening on eth0:3, link-type EN10MB (Ethernet), capture size 96 bytes
> 01:26:43.754157 IP 74.53.155.170 > 143.238.235.209: GREv1, call
> 45139, seq 0, length 36: LCP, Conf-Request (0x01), id 1, length 22
> 01:26:43.956930 IP 143.238.235.209 > 74.53.155.174: GREv1, call
> 1536, seq 0, length 40: LCP, Conf-Request (0x01), id 1, length 26

The interesting thing above is that the pptpd transmits from .170, and
the client packets are sent to .174.

There's no indication that the client packets are in response to the
server packets.  So both ends are transmitting blind to start with.

> 74.53.155.170 is the primary ip bound to eth0, 74.53.155.174 is
> eth0:3 and is what the client is trying to connect to
> ... [rewind] ...
> option /etc/ppp/options.pptpd
> debug
> logwtmp
> localip 10.101.0.1
> remoteip 10.101.0.2-102

You don't have a listen option, and so pptpd will bind to eth0 not
eth0:3.  Try adding

	listen 74.53.155.174

and restart pptpd.

> Aug 31 01:26:43 wibble pppd[31310]: sent [LCP ConfReq id=0x1
> <asyncmap 0x0> <magic 0xd4d3a867> <pcomp> <accomp>]
> Aug 31 01:26:43 wibble pptpd[31309]: GRE:
> read(fd=7,buffer=80515e0,len=8260) from network failed: status = -1
> error = Protocol not available
> 
> Which people seem to say means there is a firewall blocking things.

Yes, the firewall, a NAT gateway, the ISP, or the client, is refusing
the packet on the grounds that nothing is listening on that protocol for
packets from the address .170.  It is listening (at the time) to packets
of protocol 47 coming from address .174.

-- 
James Cameron
http://quozl.linux.org.au/

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