about freeswan connection

hi, everyone

I have tried freeswan, and vpn connection works, but it seems
something goes wrong.

freeswan version: 1.99
linux version: Redhat 7.3

The environment is:

PC1 10.0.1.23 ---- 10.0.1.12 gateway A 192.168.0.12 --
|
|
PC2 10.0.2.23 ---- 10.0.2.12 gateway B 192.168.0.13 --

the ipsec.conf in gateway A is:
################################################## ####
config setup
interfaces="ipsec0=eth0"
klipsdebug=none
plutodebug=all
plutoload=%search
plutostart=%search
uniqueids=yes

conn %default
keyingtries=0
disablearrivalcheck=no
authby=rsasig
leftrsasigkey=%dnsondemand
rightrsasigkey=%dnsondemand

conn dev1
type=tunnel
left=192.168.0.12
leftsubnet=10.0.1.0/24
right=192.168.0.13
rightsubnet=10.0.2.0/24
keyexchange=ike
keylife=1h
pfs=no
auth=esp
esp=3des-md5-96
authby=secret
keyingtries=0
auto=start
################################################## ####

the ipsec.conf in gateway B is:
################################################## ####
config setup
interfaces="ipsec0=eth0"
klipsdebug=none
plutodebug=all
plutoload=%search
plutostart=%search
uniqueids=yes

conn %default
keyingtries=0
disablearrivalcheck=no
authby=rsasig
leftrsasigkey=%dnsondemand
rightrsasigkey=%dnsondemand

conn dev2
type=tunnel
left=192.168.0.13
leftsubnet=10.0.2.0/24
right=192.168.0.12
rightsubnet=10.0.1.0/24
keyexchange=ike
keylife=1h
pfs=no
auth=esp
esp=3des-md5-96
authby=secret
keyingtries=0
auto=start
################################################## ####

The dotconf file works well.

I change "esp=3des-md5-96" to "esp=3des-sha1-96" in gateway B's
dotconf file while not change the same parameter in gateway A's
dotconf file, then reboot two machine.
I surprise to see the connection also works?!

I have checked "ipsec spi" and get the following information:

tun0x1006@192.168.0.13 IPIP: dir=out src=192.168.0.12
life(c,s,h)=bytes(7440,0,0)addtime(93,0,0)usetime( 92,0,0)packets(93,0,0)
idle=0
tun0x1005@192.168.0.12 IPIP: dir=in src=192.168.0.13
policy=10.0.2.0/24->10.0.1.0/24 flags=0x8<>
life(c,s,h)=bytes(7360,0,0)addtime(93,0,0)usetime( 91,0,0)packets(92,0,0)
idle=0
tun0x1004@192.168.0.13 IPIP: dir=out src=192.168.0.12
life(c,s,h)=bytes(160,0,0)addtime(95,0,0)usetime(9 4,0,0)packets(2,0,0)
idle=93
tun0x1003@192.168.0.12 IPIP: dir=in src=192.168.0.13
policy=10.0.2.0/24->10.0.1.0/24 flags=0x8<>
life(c,s,h)=bytes(160,0,0)addtime(95,0,0)usetime(9 3,0,0)packets(2,0,0)
idle=92
tun0x1002@192.168.0.13 IPIP: dir=out src=192.168.0.12
life(c,s,h)=bytes(1280,0,0)addtime(110,0,0)usetime (110,0,0)packets(16,0,0)
idle=95
tun0x1001@192.168.0.12 IPIP: dir=in src=192.168.0.13
policy=10.0.2.0/24->10.0.1.0/24 flags=0x8<>
life(c,s,h)=bytes(1360,0,0)addtime(117,0,0)usetime (110,0,0)packets(17,0,0)
idle=94
esp0x6e0e8f7b@192.168.0.12 ESP_3DES_HMAC_MD5: dir=in src=192.168.0.13
iv_bits=64bits iv=0x28671ca350a8b436 ooowin=64 seq=92
bit=0xffffffffffffffff alen=128 aklen=128 eklen=192
life(c,s,h)=bytes(7360,0,0)addtime(93,0,0)usetime( 91,0,0)packets(92,0,0)
idle=0
esp0x6e0e8f7a@192.168.0.12 ESP_3DES_HMAC_MD5: dir=in src=192.168.0.13
iv_bits=64bits iv=0x969100fec7469045 ooowin=64 seq=2 bit=0x3 alen=128
aklen=128 eklen=192 life(c,s,h)=bytes(160,0,0)addtime(95,0,0)usetime(9 3,0,0)packets(2,0,0)
idle=92
esp0x6e0e8f79@192.168.0.12 ESP_3DES_HMAC_MD5: dir=in src=192.168.0.13
iv_bits=64bits iv=0xf90911d581bcf48f ooowin=64 seq=17 bit=0x1ffff
alen=128 aklen=128 eklen=192
life(c,s,h)=bytes(1360,0,0)addtime(117,0,0)usetime (110,0,0)packets(17,0,0)
idle=94
esp0xab87e960@192.168.0.13 ESP_3DES_HMAC_MD5: dir=out src=192.168.0.12
iv_bits=64bits iv=0xe706fa96ea1268df ooowin=64 seq=93 alen=128
aklen=128 eklen=192 life(c,s,h)=bytes(10416,0,0)addtime(93,0,0)usetime (92,0,0)packets(93,0,0)
idle=0
esp0xab87e95f@192.168.0.13 ESP_3DES_HMAC_MD5: dir=out src=192.168.0.12
iv_bits=64bits iv=0x2f73c20d8b0b70be ooowin=64 seq=2 alen=128
aklen=128 eklen=192 life(c,s,h)=bytes(224,0,0)addtime(95,0,0)usetime(9 4,0,0)packets(2,0,0)
idle=93
esp0xab87e95e@192.168.0.13 ESP_3DES_HMAC_MD5: dir=out src=192.168.0.12
iv_bits=64bits iv=0x996cb93412db2cce ooowin=64 seq=16 alen=128
aklen=128 eklen=192 life(c,s,h)=bytes(1792,0,0)addtime(110,0,0)usetime (110,0,0)packets(16,0,0)
idle=95

I do not know where I have a mistake.
Thank you.