strongSwan

hi,

i get this issue below. please help.

our local network works well, and we can ping or telnet the host running strongswan client.
however strongswan client on the host reports this error "error writing to socket: Network is unreachable" when it initiates IKE message to secgw server.
if i reboot the host, then ipsec tunnel established between the host and secgw server.

2019.08.22_18.50.54 05[CFG] received stroke: add connection 'IPsecConn_f3p1c2'
2019.08.22_18.50.54 05[CFG] conn IPsecConn_f3p1c2
2019.08.22_18.50.54 05[CFG] left=10.10.100.67
2019.08.22_18.50.54 05[CFG] leftsubnet=0.0.0.0/0
2019.08.22_18.50.54 05[CFG] leftsourceip=
2019.08.22_18.50.54 05[CFG] leftauth=pubkey
2019.08.22_18.50.54 05[CFG] leftid=C=CN,ST=GD,L=GZ,O=zhaobiao,CN=002A2B00AA58@AP.comba.com.cn
2019.08.22_18.50.54 05[CFG] leftcert=f3p1c2-681D640000000000.-cert.pem
2019.08.22_18.50.54 05[CFG] right=20.0.0.2
2019.08.22_18.50.54 05[CFG] rightsubnet=0.0.0.0/0
2019.08.22_18.50.54 05[CFG] rightauth=pubkey
2019.08.22_18.50.54 05[CFG] rightid=C=CN,ST=GD,L=GZ,O=zhaobiao,CN=002A2B00AA61@AP.comba.com.cn
2019.08.22_18.50.54 05[CFG] aaa_identity=
2019.08.22_18.50.54 05[CFG] xauth_identity=
2019.08.22_18.50.54 05[CFG] ike=aes-sha1-prfsha1-modp1024!
2019.08.22_18.50.54 05[CFG] esp=aes-sha1-modp1024!
2019.08.22_18.50.54 05[CFG] dpddelay=30
2019.08.22_18.50.54 05[CFG] dpdtimeout=150
2019.08.22_18.50.54 05[CFG] mediation=no
2019.08.22_18.50.54 05[CFG] keyexchange=ikev2
2019.08.22_18.50.54 05[CFG] loaded certificate "C=CN, ST=GD, L=GZ, O=zhaobiao, CN=002A2B00AA58@AP.comba.com.cn" from 'f3p1c2-681D640000000000.-cert.pem'
2019.08.22_18.50.54 05[CFG] added configuration 'IPsecConn_f3p1c2'
2019.08.22_18.50.56 03[CFG] received stroke: initiate 'IPsecConn_f3p1c2'
2019.08.22_18.50.56 03[IKE] initiating IKE_SA IPsecConn_f3p1c2¹ to 20.0.0.2
2019.08.22_18.50.56 03[CFG] configured proposals: IKE:AES_CBC_128/HMAC_SHA1_96/PRF_HMAC_SHA1/MODP_1024
2019.08.22_18.50.56 03[ENC] generating IKE_SA_INIT request 0 [ SA KE No N(NATD_S_IP) N(NATD_D_IP) N(HASH_ALG) ]
2019.08.22_18.50.56 03[NET] sending packet: from 10.10.100.67⁵⁰⁰ to 20.0.0.2⁵⁰⁰ (320 bytes)
2019.08.22_18.50.56 10[NET] error writing to socket: Network is unreachable
2019.08.22_18.51.00 02[IKE] retransmit 1 of request with message ID 0
2019.08.22_18.51.00 02[NET] sending packet: from 10.10.100.67⁵⁰⁰ to 20.0.0.2⁵⁰⁰ (320 bytes)
2019.08.22_18.51.00 10[NET] error writing to socket: Network is unreachable
2019.08.22_18.51.08 07[IKE] retransmit 2 of request with message ID 0
2019.08.22_18.51.08 07[NET] sending packet: from 10.10.100.67⁵⁰⁰ to 20.0.0.2⁵⁰⁰ (320 bytes)
2019.08.22_18.51.08 10[NET] error writing to socket: Network is unreachable
2019.08.22_18.51.21 08[IKE] giving up after 2 retransmits

zhonghai li