调试 SSHD 在无线网络上对转发的请求没有响应

我正在努力弄清楚为什么 sshd 没有响应传入的请求。我有一个通过无线连接到 Linksys 路由器的 ubuntu 18.04 系统。

Router:  10.132.2.1
Computer: 10.132.2.20  This is a static IP address on wlp1s0

sshd 正在侦听端口 20（选择奇怪端口的原因并不重要）。

我在计算机上运行 /usr/sbin/sshd -dddD 并查看：

debug1: Bind to port 20 on 10.132.2.20
Server listening on 10.132.2.20 port 20

我尝试使用 ssh -vv -p 20 从另一台计算机上的 WAN 连接到 ssh，然后查看：

debug2: ssh_connect_direct
debug1: Connecting to  [  ] port 20.

在计算机 10.132.2.20 上的一个单独窗口中，我运行 tcpdump -i wlp1s0 port 20 -n -Q inout 并查看：

10:05:29.787051 IP 107.77.240.93.40190 > 10.132.2.20.20: Flags [s], seq 1030904803, win 64240, options [mss 1390,sackOK,TS val 1967897638 ecr 0,nop,wscale 7], length 0

sshd 没有输出。

编辑：

作为调试的一部分，我尝试将计算机连接到为 WIFI 提供服务的路由器。这有效。我能够从 WAN 连接到与无线连接关联的 IP 地址。再次将有线连接切换回 10.132.1 网络导致 10.132.2 ssh 连接失败。所以问题与生活在两个不同网络上的 ssh 有关。我尝试制作 sshd 服务的副本，这样我就有一个服务于 10.132.1.* 网络，另一个服务于 10.132.2.* 网络。这再次失败，但同样，仅当计算机位于两个网络上时。如果有线网络和无线网络在同一个路由器上，那么它可以工作。

编辑2：

这是 ip route 的输出（我不知道如何解码这里的所有内容——在我的基本理解中，看起来有两个网络，10.132.1.1 优先级（指标 100）超过 10.132.2.1）

default via 10.132.1.1 dev eno1 proto dhcp metric 100 
default via 10.132.2.1 dev wlp1s0 proto dhcp metric 600 
10.132.1.0/24 dev eno1 proto kernel scope link src 10.132.1.10 metric 100 
10.132.2.0/24 dev wlp1s0 proto kernel scope link src 10.132.2.20 metric 600 
169.254.0.0/16 dev wlp1s0 scope link metric 1000 

最后，这里是原始的sshd_config文件（注：10.132.1.10是电脑所在的有线网络——ssh在有线网络上没有问题）：

#   $OpenBSD: sshd_config,v 1.101 2017/03/14 07:19:07 djm Exp $

# This is the sshd server system-wide configuration file.  See
# sshd_config(5) for more information.

# This sshd was compiled with PATH=/usr/bin:/bin:/usr/sbin:/sbin

# The strategy used for options in the default sshd_config shipped with
# OpenSSH is to specify options with their default value where
# possible, but leave them commented.  Uncommented options override the
# default value.

Port 20
Port 22
#Port 80

#Port 22
#AddressFamily any
ListenAddress 10.132.2.20:20
ListenAddress 10.132.1.10:22
#ListenAddress 0.0.0.0
#ListenAddress ::

#HostKey /etc/ssh/ssh_host_rsa_key
#HostKey /etc/ssh/ssh_host_ecdsa_key
#HostKey /etc/ssh/ssh_host_ed25519_key

# Ciphers and keying
#RekeyLimit default none

# Logging
#SyslogFacility AUTH
#LogLevel INFO

# Authentication:

#LoginGraceTime 2m
#PermitRootLogin prohibit-password
#StrictModes yes
#MaxAuthTries 6
#MaxSessions 10

#PubkeyAuthentication yes

# Expect .ssh/authorized_keys2 to be disregarded by default in future.
#AuthorizedKeysFile .ssh/authorized_keys .ssh/authorized_keys2

#AuthorizedPrincipalsFile none

#AuthorizedKeysCommand none
#AuthorizedKeysCommandUser nobody

# For this to work you will also need host keys in /etc/ssh/ssh_known_hosts
#HostbasedAuthentication no
# Change to yes if you don't trust ~/.ssh/known_hosts for
# HostbasedAuthentication
#IgnoreUserKnownHosts no
# Don't read the user's ~/.rhosts and ~/.shosts files
#IgnoreRhosts yes

# To disable tunneled clear text passwords, change to no here!
#PasswordAuthentication yes
#PermitEmptyPasswords no

# Change to yes to enable challenge-response passwords (beware issues with
# some PAM modules and threads)
ChallengeResponseAuthentication no

# Kerberos options
#KerberosAuthentication no
#KerberosOrLocalPasswd yes
#KerberosTicketCleanup yes
#KerberosGetAFSToken no

# GSSAPI options
#GSSAPIAuthentication no
#GSSAPICleanupCredentials yes
#GSSAPIStrictAcceptorCheck yes
#GSSAPIKeyExchange no

# Set this to 'yes' to enable PAM authentication, account processing,
# and session processing. If this is enabled, PAM authentication will
# be allowed through the ChallengeResponseAuthentication and
# PasswordAuthentication.  Depending on your PAM configuration,
# PAM authentication via ChallengeResponseAuthentication may bypass
# the setting of "PermitRootLogin without-password".
# If you just want the PAM account and session checks to run without
# PAM authentication, then enable this but set PasswordAuthentication
# and ChallengeResponseAuthentication to 'no'.
UsePAM yes

#AllowAgentForwarding yes
#AllowTcpForwarding yes
#GatewayPorts yes
X11Forwarding yes
#X11DisplayOffset 10
#X11UseLocalhost yes
#PermitTTY yes
PrintMotd no
#PrintLastLog yes
#TCPKeepAlive yes
#UseLogin no
#PermitUserEnvironment no
#Compression delayed
#ClientAliveInterval 0
#ClientAliveCountMax 3
UseDNS no
#PidFile /var/run/sshd.pid
#MaxStartups 10:30:100
#PermitTunnel no
#ChrootDirectory none
#VersionAddendum none

# no default banner path
#Banner none

# Allow client to pass locale environment variables
AcceptEnv LANG LC_*

# override default of no subsystems
Subsystem   sftp    /usr/lib/openssh/sftp-server

# Example of overriding settings on a per-user basis
#Match User anoncvs
#   X11Forwarding no
#   AllowTcpForwarding no
#   PermitTTY no
#   ForceCommand cvs server