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我正在使用 ipsec vpn 客户端连接远程主机。由于远程主机只接受一个 IP 地址，因此我在 enc0 上为本地网络设置了 nat。从 ipsec 主机 Ping 正常：
PING 172.20.162.150 (172.20.162.150): 56 data bytes
64 bytes from 172.20.162.150: icmp_seq=0 ttl=252 time=2.597 ms
但是从本地网络 ping 失败：
PING 172.20.162.150 (172.20.162.150) 56(84) bytes of data.
From 192.168.1.5 icmp_seq=1 Frag needed and DF set (mtu = 0)
enc0 = 0 的 MTU，我无法更改它
netstat -i
Name Mtu Network Address Ipkts Ierrs Opkts Oerrs Colls
enc0 0 <Link> 29 0 29 0 0
enc0 0 172.25.41.1 172.25.41.10 29 0 29 0 0
我尝试在 pf.conf 中使用磨砂，但没有帮助：
match in on enc0 scrub (no-df max-mss 1300)
or match in all scrub (no-df max-mss 1300)
sudo ifconfig enc0 mtu 1452 返回：
SIOCSIFMTU: Inappropriate ioctl for device
不幸的是，没有解决方案选项（（（
其他可能有助于理解的设置：
172.20.162.150 - remote host
172.25.41.10 - local ip for enc0 (only this ip accepted by 172.20.162.150)
192.168.1.0/24 local net and 192.168.1.5 ip of my host for local net
/etc/hostname.enc0
inet 172.25.41.10 255.255.255.255
up
!/sbin/route add -host 172.20.162.150 172.25.41.10
/etc/ipsec.conf
ike esp from 172.25.41.10/32 to 172.20.162.150/32 peer 80.*.*.132 \
main auth hmac-sha1 enc aes-256 group modp1024 lifetime 86400 \
quick auth hmac-sha1 enc aes-256 group modp1024 lifetime 3600 \
psk ***********
/etc/pf.conf
pass from 172.20.162.150 to any
pass out quick on enc0 from <localnet> to 172.20.162.150 nat-to enc0 keep state (if-bound)
tcpdump for ping from local net for internal net if
192.168.1.13 > 172.20.162.150: icmp: echo request (id:777a seq:5) [icmp cksum ok] (DF) (ttl 64, id 30758, len 84)
192.168.1.5 > 192.168.1.13: icmp: 172.20.162.150 unreachable - need to frag [icmp cksum ok] (ttl 255, id 44410, len 56, bad ip cksum 0! -> 8ae7)
tcpdump for enc0 is empty.
Statistic for nat from pfctl:
sudo pfctl -s state | grep 172.20.162.150
all icmp 172.20.162.150:8 <- 192.168.1.13:30586 0:0
enc0 icmp 172.25.41.10:61751 (192.168.1.13:30586) -> 172.20.162.150:8 0:0
有人遇到类似的问题，能及时解决吗？