Tim, dengan hormat saya mendorong Anda untuk mengabaikan keraguan Anda tentang perubahan MTU. Masalah Anda memiliki masalah MTU yang ditulis di atasnya dan saya telah menjadi insinyur jaringan profesional selama lebih dari 15 tahun.
Untuk membuktikan apakah MTU membantu, lakukan tes dari mesin linux Anda menggunakan ping dengan DF
bit yang diatur di header IP ...
ping -M do -s 1232 <some pingable internet ip address>
Saya menghitung -s
parameter dengan asumsi PPPoE IP MTU Anda adalah 1300 byte. Jika ping itu berhasil, gunakan -s 1472
dan perhatikan apa yang terjadi ... jika ping itu gagal, Anda memiliki bukti konklusif bahwa ada masalah MTU (dengan asumsi Anda belum menyetel MTU tautan Ethernet Anda lebih rendah). FYI, -s 1472
akan mengirimkan permintaan echo-ethernet-payload 1500-byte; -M do -s 1472
mengirimkan muatan 1500-byte yang sama dengan set DF-bit di header IP.
Ingat juga bahwa MTU harus disetel di kedua sisi tautan ... jadi Anda perlu melakukan ini pada modem Anda juga.
EDIT
Tim, Anda masih belum menjalankan perintah yang saya minta . Biarkan saya memberi Anda contoh apa yang salah dengan apa yang Anda lakukan (saya perlu memodifikasi host tujuan ke stackexchange.com, karena firewall untuk fragmentasi IP di jalur saya ke 8.8.8.8)
Contoh negatif (menggunakan flag ping Anda)
[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 ~]$
Pertanyaan retoris: bagaimana paket ping 64KB dapat melewati segmen ethernet 1500-byte? (lihat Catatan akhir A) Saya tidak dapat membantu kecuali Anda memposting informasi yang saya minta. Ini adalah contoh yang sama, denganping -M do
Contoh positif
[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
memberikan informasi tentang MTU maksimum di sepanjang jalan (dalam hal ini, kita tahu segmen ethernet hop pertama memiliki IP MTU
1500-byte).
Catatan Akhir:
A. Ping Anda dapat diselesaikan sebagai serangkaian fragmen IP, karena secara default ping
memungkinkan fragmentasi IP. Jika Anda mencoba menemukan ukuran paket maksimum yang akan melewati tautan, Anda harus memodifikasi header IP (yang saya ilustrasikan dengan -M do
) untuk memastikan Anda tidak mendapatkan banyak tanggapan terfragmentasi yang dijahit bersama di akhir. Menggunakan 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