Tim, I respectfully urge you to ignore your doubts about changing MTU. Your issue has MTU problem written all over it and I have been a professional network engineer for over 15 years.
To prove whether MTU helps, conduct tests from your linux machine using ping with the DF
bit set in the IP header...
ping -M do -s 1232 <some pingable internet ip address>
I calculated the -s
parameter assuming your PPPoE IP MTU is 1300 bytes. If that ping succeeds, then use -s 1472
and watch what happens... if the ping it now fails, you have conclusive proof that there is an MTU issue (assuming you have not set your Ethernet link MTU lower). FYI, -s 1472
will send a 1500-byte ethernet-payload echo-request; -M do -s 1472
sends that same 1500-byte payload with the DF-bit set in the IP header.
Also remember that MTU must be set on both sides of the link... so you would need to do this on your modem as well.
EDIT
Tim, you still have not run the commands I asked you to. Let me give you an example of what is wrong with what you did (I need to modify the destination host to stackexchange.com, due to firewalling for IP fragmentation in my path to 8.8.8.8)
Negative example (using your ping flags)
[mpenning@Bucksnort ~]$ ping -c 1 -s 65507 64.34.119.12
PING 64.34.119.12 (64.34.119.12) 65507(65535) bytes of data.
65515 bytes from 64.34.119.12: icmp_seq=1 ttl=51 time=53.2 ms
--- 64.34.119.12 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 53.246/53.246/53.246/0.000 ms
[mpenning@Bucksnort ~]$
Rhetorical question: how did a 64KB ping packet get through a 1500-byte ethernet segment? (see End note A) I can't help unless you post the information I am asking for. This is the same example, with ping -M do
Positive example
[mpenning@Bucksnort ~]$ ping -M do -c 1 -s 65507 64.34.119.12
PING 64.34.119.12 (64.34.119.12) 65507(65535) bytes of data.
From 24.102.60.3 icmp_seq=1 Frag needed and DF set (mtu = 1500)
--- 64.34.119.12 ping statistics ---
0 packets transmitted, 0 received, +1 errors
[mpenning@Bucksnort ~]$
ping -M do
provides information about the maximum MTU along the path (in this case, we know the first-hop ethernet segment has an IP MTU
of 1500-bytes).
End Notes:
A. Your pings can be completed as a series of IP fragments, because by-default ping
allows IP fragmentation. If you are trying to find the maximum packet size that will pass through a link, you must modify the IP header (which I illustrated with -M do
) to ensure you don't get a bunch of fragmented responses stitched together at the end. Using ping -c 1 -s 65507 64.34.119.12
:
[mpenning@Bucksnort ~]$ sudo tshark -n -i eth0 icmp
1 0.000000 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=0)
2 0.000058 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=1480)
3 0.000071 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=2960)
4 0.000081 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=4440)
5 0.000094 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=5920)
6 0.000105 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=7400)
7 0.000116 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=8880)
8 0.000124 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=10360)
9 0.000133 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=11840)
10 0.000143 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=13320)
11 0.000152 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=14800)
12 0.000162 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=16280)
13 0.000172 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=17760)
14 0.000181 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=19240)
15 0.000191 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=20720)
16 0.000201 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=22200)
17 0.000211 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=23680)
18 0.000221 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=25160)
19 0.000230 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=26640)
20 0.000240 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=28120)
21 0.000250 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=29600)
22 0.000259 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=31080)
23 0.000269 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=32560)
24 0.000278 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=34040)
25 0.000288 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=35520)
26 0.000298 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=37000)
27 0.000308 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=38480)
28 0.000318 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=39960)
29 0.000327 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=41440)
30 0.000337 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=42920)
31 0.000352 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=44400)
32 0.000361 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=45880)
33 0.000372 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=47360)
34 0.000384 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=48840)
35 0.000394 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=50320)
36 0.000403 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=51800)
37 0.000411 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=53280)
38 0.000419 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=54760)
39 0.000428 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=56240)
40 0.000437 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=57720)
41 0.000446 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=59200)
42 0.000455 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=60680)
43 0.000466 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=62160)
44 0.000477 24.102.60.3 -> 64.34.119.12 IP Fragmented IP protocol (proto=ICMP 0x01, off=63640)
45 0.000486 24.102.60.3 -> 64.34.119.12 ICMP Echo (ping) request
46 0.044402 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=0)
47 0.044439 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=1480)
48 0.044899 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=2960)
49 0.044910 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=4440)
50 0.044916 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=5920)
51 0.045149 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=7400)
52 0.045399 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=8880)
53 0.045409 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=10360)
54 0.045415 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=11840)
55 0.045649 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=13320)
56 0.045899 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=14800)
57 0.045908 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=16280)
58 0.045915 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=17760)
59 0.046148 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=19240)
60 0.046163 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=20720)
61 0.046402 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=22200)
62 0.046421 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=23680)
63 0.046650 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=25160)
64 0.046668 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=26640)
65 0.046901 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=28120)
66 0.046918 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=29600)
67 0.047151 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=31080)
68 0.047171 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=32560)
69 0.047399 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=34040)
70 0.047418 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=35520)
71 0.047424 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=37000)
72 0.047650 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=38480)
73 0.047900 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=39960)
74 0.048149 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=41440)
75 0.048165 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=42920)
76 0.048172 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=44400)
77 0.048178 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=45880)
78 0.048398 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=47360)
79 0.048650 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=48840)
80 0.048667 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=50320)
81 0.048674 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=51800)
82 0.048900 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=53280)
83 0.048922 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=54760)
84 0.049150 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=56240)
85 0.049174 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=57720)
86 0.049398 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=59200)
87 0.049649 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=60680)
88 0.049671 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=62160)
89 0.049677 64.34.119.12 -> 24.102.60.3 IP Fragmented IP protocol (proto=ICMP 0x01, off=63640)
90 0.049683 64.34.119.12 -> 24.102.60.3 ICMP Echo (ping) reply
Best Answer
I'm on Debian at the moment, and I see both a client (package
mactelnet-client
) and server (predictably,mactelnet-server
). In the case of the client,mactelnet
is the binary to run. I'd be very wary of the security aspect in a piece of software like this, though. Linux TCP/IP has a well-established, peer-reviewed, often audited stack and toolset.However, as other(s) have mentioned already, if you need a remote-access console for your computer, invest in a machine with IPMI 2.0 or similar management subsystem, or buy an RS-232-to-ethernet adaptor and configure a serial
getty
on your computer. The former allows you access to the computer's BIOS/NVRAM, the latter doesn't unless your computer has ‘Serial Redirection’ support (Dell servers do, for one).It's interesting that on non-PC servers (e.g. SPARC machines), this sort of thing is the norm. Our Sun T100-based boxes don't even have keyboard or display ports. All management is done via a serial or ethernet console. Older Suns automatically use the first serial port as the console unless a keyboard is plugged in on boot.