Re: Help, I have some problem with LCP ConfReq

i see, thank you for your help!

On Mon, Apr 11, 2011 at 3:59 PM, James Cameron <[email protected]> wrote:
> On Mon, Apr 11, 2011 at 03:52:13PM +0800, Benimaur Gao wrote:
>> Server Side:
>>
>> skyxen:~# tcpdump -ni eth0 host 121.0.29.193 and proto gre
>> tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
>> listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes
>> 14:59:43.829782 IP 199.68.197.202 > 121.0.29.193: GREv1, call 59360,
>> seq 0, length 41: LCP, Conf-Request (0x01), id 1, length 27
>> 14:59:44.014911 IP 121.0.29.193 > 199.68.197.202: GREv1, call 1536,
>> seq 1, length 36: LCP, Conf-Request (0x01), id 1, length 22
>
> Positive proof that server is emitting GRE.
>
> The server understands the client IP is 121.0.29.193.
>
>> Client(from my debian):
>> skyshouter:/home/benimaur# tcpdump -ni eth1 proto gre and host 199.68.197.202
>> tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
>> listening on eth1, link-type EN10MB (Ethernet), capture size 65535 bytes
>> 15:06:56.957177 IP 10.16.2.60 > 199.68.197.202: GREv1, call 1536, seq
>> 1, length 36: LCP, Conf-Request (0x01), id 1, length 22
>> 15:06:59.581653 IP 10.16.2.60 > 199.68.197.202: GREv1, call 1536, seq
>> 2, length 36: LCP, Conf-Request (0x01), id 1, length 22
>> 15:07:02.581648 IP 10.16.2.60 > 199.68.197.202: GREv1, call 1536, seq
>> 3, length 36: LCP, Conf-Request (0x01), id 1, length 22
>
> Positive proof that network is not supplying any of the server GRE
> packets to the client.
>
> Positive proof that the client is behind a NAT router of some sort;
> since the IP address is in 10/8 range.  This means the NAT router is
> responsible for readdressing the packets.
>
>> Client(created by wireshark):
>>
>> skyshouter:/home/benimaur/share/incoming# tcpdump -r temp.pcap host
>> 199.68.197.202 and proto gre
>> reading from file temp.pcap, link-type EN10MB (Ethernet)
>> 15:29:54.390057 IP 10.16.2.128 > 199.68.197.202: GREv1, call 1792, seq
>> 0, length 37: LCP, Conf-Request (0x01), id 0, length 23
>> 15:29:54.578682 IP 199.68.197.202 > 10.16.2.128: GREv1, call 16384,
>> seq 1, ack 0, length 27: LCP, Conf-Reject (0x04), id 0, length 9
>
> Positive proof that the NAT router is capable of readdressing the
> packets.
>
> Theory: the NAT router only supports Windows PPTP.
>
>> It seems that GRE packes must be dropped somewhere, and is there any
>> means to solve this problem?
>
> No, not unless you can fix the NAT router.
>
> You might use OpenVPN instead, since it does not require such excellence
> and processing by a NAT router.
>
> To identify the NAT router, it is the device that has the IP address
> 121.0.29.193.
>
> --
> James Cameron
> http://quozl.linux.org.au/
>

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