我通过 ppp 连接了这两台计算机。
一个有 ip 10.10.0.1，另一个有 ip 10.10.0.2。
ppp0两者都有带有网络掩码的接口255.255.255.255：
# ifconfig
ppp0: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST> mtu 1500
inet 10.10.0.2 netmask 255.255.255.255 destination 10.10.0.1
ppp txqueuelen 3 (Point-to-Point Protocol)
RX packets 7 bytes 105 (105.0 B)
RX errors 3 dropped 0 overruns 0 frame 0
TX packets 20 bytes 1522 (1.4 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
如何才能使用 SSH10.10.0.2进行连接？10.10.0.1
如果我做：
# ssh -vv [email protected]
我可以看到它被冻结在：
.
.
.
password:
debug2: input_userauth_info_req
debug2: input_userauth_info_req: num_prompts 0
debug1: Authentication succeeded (keyboard-interactive).
Authenticated to 10.10.0.1 ([10.10.0.1]:22).
debug1: channel 0: new [client-session]
debug2: channel 0: send open
debug1: Requesting [email protected]
debug1: Entering interactive session.
debug1: pledge: network
从 tcpdump 观看所有内容，我看到：
# tcpdump -i ppp0
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on ppp0, link-type LINUX_SLL (Linux cooked), capture size 262144 bytes
22:15:48.592651 IP tlcmelo > 10.100.0.1: ICMP echo request, id 17288, seq 1, length 64
22:15:48.942907 IP 10.100.0.1 > tlcmelo: ICMP echo reply, id 17288, seq 1, length 64
22:15:49.593728 IP tlcmelo > 10.100.0.1: ICMP echo request, id 17288, seq 2, length 64
22:15:49.821594 IP 10.100.0.1 > tlcmelo: ICMP echo reply, id 17288, seq 2, length 64
22:15:50.595483 IP tlcmelo > 10.100.0.1: ICMP echo request, id 17288, seq 3, length 64
22:15:50.840112 IP 10.100.0.1 > tlcmelo: ICMP echo reply, id 17288, seq 3, length 64
22:15:51.597014 IP tlcmelo > 10.100.0.1: ICMP echo request, id 17288, seq 4, length 64
22:16:00.105020 IP tlcmelo.57621 > 10.100.0.1.57621: UDP, length 44
22:16:38.104153 IP tlcmelo.57621 > 10.100.0.1.57621: UDP, length 44
22:17:04.490191 IP tlcmelo.37489 > 239.255.255.250.1900: UDP, length 171
22:17:05.490773 IP tlcmelo.37489 > 239.255.255.250.1900: UDP, length 171
22:17:06.491775 IP tlcmelo.37489 > 239.255.255.250.1900: UDP, length 171
22:17:07.492280 IP tlcmelo.37489 > 239.255.255.250.1900: UDP, length 171
22:17:16.104112 IP tlcmelo.57621 > 10.100.0.1.57621: UDP, length 44
22:17:54.103994 IP tlcmelo.57621 > 10.100.0.1.57621: UDP, length 44
22:18:32.105034 IP tlcmelo.57621 > 10.100.0.1.57621: UDP, length 44
编辑1：
@derobert，感谢您的消息：实际上也不可能从10.10.0.1back ssh 到10.10.0.2，同样的问题。我尝试了较小的 MTU，不幸的是没有成功。
@pizdelect，感谢您的留言：我在两台计算机上都运行 debian。我尝试将 MTU 设置为 1000 和 500，但尚未成功。
编辑2：
在 中10.10.0.1，iptables -vL我看到了这些：
Chain Block (2 references)
pkts bytes target prot opt in out source destination
75 3210 LOG all -- any any anywhere !0.0.0.255/-1 limit: avg 3/hour burst 5 LOG level warning prefix "Iptables: Block: "
6 360 REJECT tcp -- any any anywhere anywhere reject-with tcp-reset
2433 143K REJECT udp -- any any anywhere anywhere reject-with icmp-port-unreachable
0 0 DROP all -- any any anywhere anywhere
是否有可能它阻止了连接？