caso roadwarrior estabelecendo IKE_SA falhou, peer não responde

Estou tentando implementar o caso roadwarrior usando strongswan. Neste caso, o cliente VPN está enviando uma solicitação para o gateway, mas o gateway simplesmente descarta o pacote. Eu me certifiquei de que apenas charon-systemdele está em execução. Basicamente, eu removo outros pacotes usando

sudo apt install -y strongswan charon-systemd strongswan-swanctl strongswan-pki libstrongswan-extra-plugins libtss2-tcti-tabrmd0
sudo apt remove -y strongswan-starter strongswan-charon

Mesmo em ss -tunlpum gateway podemos ver charon-systemdque ele está escutando portas

Netid  State   Recv-Q  Send-Q   Local Address:Port   Peer Address:Port Process                                                                                                                                     
udp    UNCONN  0       0           127.0.0.54:53          0.0.0.0:*     users:(("systemd-resolve",pid=1265,fd=19))                                                                                                 
udp    UNCONN  0       0        127.0.0.53%lo:53          0.0.0.0:*     users:(("systemd-resolve",pid=1265,fd=17))                                                                                                 
udp    UNCONN  0       0              0.0.0.0:68          0.0.0.0:*     users:(("charon-systemd",pid=1420,fd=22))                                                                                                  
udp    UNCONN  0       0              0.0.0.0:111         0.0.0.0:*     users:(("rpcbind",pid=1264,fd=5),("systemd",pid=1,fd=37))                                                                                  
udp    UNCONN  0       0            127.0.0.1:323         0.0.0.0:*     users:(("chronyd",pid=1382,fd=5))                                                                                                          
udp    UNCONN  0       0              0.0.0.0:500         0.0.0.0:*     users:(("charon-systemd",pid=1420,fd=15))                                                                                                  
udp    UNCONN  0       0              0.0.0.0:4500        0.0.0.0:*     users:(("charon-systemd",pid=1420,fd=16))                                                                                                  
udp    UNCONN  0       0              0.0.0.0:5355        0.0.0.0:*     users:(("systemd-resolve",pid=1265,fd=11))                                                                                                 
udp    UNCONN  0       0                 [::]:111            [::]:*     users:(("rpcbind",pid=1264,fd=7),("systemd",pid=1,fd=39))                                                                                  
udp    UNCONN  0       0                [::1]:323            [::]:*     users:(("chronyd",pid=1382,fd=6))                                                                                                          
udp    UNCONN  0       0                 [::]:500            [::]:*     users:(("charon-systemd",pid=1420,fd=13))                                                                                                  
udp    UNCONN  0       0                 [::]:4500           [::]:*     users:(("charon-systemd",pid=1420,fd=14))                                                                                                  
udp    UNCONN  0       0                 [::]:5355           [::]:*     users:(("systemd-resolve",pid=1265,fd=13))                                                                                                 
tcp    LISTEN  0       20           127.0.0.1:25          0.0.0.0:*     users:(("exim4",pid=1864,fd=4))                                                                                                            
tcp    LISTEN  0       4096        127.0.0.54:53          0.0.0.0:*     users:(("systemd-resolve",pid=1265,fd=20))                                                                                                 
tcp    LISTEN  0       4096           0.0.0.0:5355        0.0.0.0:*     users:(("systemd-resolve",pid=1265,fd=12))                                                                                                 
tcp    LISTEN  0       4096           0.0.0.0:3128        0.0.0.0:*     users:(("spiceproxy work",pid=1923,fd=6),("spiceproxy",pid=1922,fd=6))                                                                     
tcp    LISTEN  0       128            0.0.0.0:22          0.0.0.0:*     users:(("sshd",pid=1387,fd=3))                                                                                                             
tcp    LISTEN  0       4096           0.0.0.0:111         0.0.0.0:*     users:(("rpcbind",pid=1264,fd=4),("systemd",pid=1,fd=36))                                                                                  
tcp    LISTEN  0       4096     127.0.0.53%lo:53          0.0.0.0:*     users:(("systemd-resolve",pid=1265,fd=18))                                                                                                 
tcp    LISTEN  0       4096              [::]:5355           [::]:*     users:(("systemd-resolve",pid=1265,fd=14))                                                                                                 
tcp    LISTEN  0       128               [::]:22             [::]:*     users:(("sshd",pid=1387,fd=4))                                                                                                             
tcp    LISTEN  0       4096              [::]:111            [::]:*     users:(("rpcbind",pid=1264,fd=6),("systemd",pid=1,fd=38))                                                                                  
tcp    LISTEN  0       20               [::1]:25             [::]:*     users:(("exim4",pid=1864,fd=5))  

O cliente tenta iniciar a solicitação, mas não recebe nenhuma resposta do gateway

Nov 21 20:32:40 client-node charon-systemd[3938]: retransmit 1 of request with message ID 0
Nov 21 20:32:40 client-node charon-systemd[3938]: sending packet: from <REDACTED>[500] to <REDACTED>[500] (1048 bytes)
Nov 21 20:32:48 client-node charon-systemd[3938]: retransmit 2 of request with message ID 0
Nov 21 20:32:48 client-node charon-systemd[3938]: sending packet: from <REDACTED>[500] to <REDACTED>[500] (1048 bytes)
Nov 21 20:33:00 client-node charon-systemd[3938]: retransmit 3 of request with message ID 0
Nov 21 20:33:00 client-node charon-systemd[3938]: sending packet: from <REDACTED>[500] to <REDACTED>[500] (1048 bytes)
Nov 21 20:33:24 client-node charon-systemd[3938]: retransmit 4 of request with message ID 0
Nov 21 20:33:24 client-node charon-systemd[3938]: sending packet: from <REDACTED>[500] to <REDACTED>[500] (1048 bytes)
Nov 21 20:34:06 client-node charon-systemd[3938]: retransmit 5 of request with message ID 0
Nov 21 20:34:06 client-node charon-systemd[3938]: sending packet: from <REDACTED>[500] to <REDACTED>[500] (1048 bytes)
Nov 21 20:35:21 client-node charon-systemd[3938]: giving up after 5 retransmits
Nov 21 20:35:21 client-node charon-systemd[3938]: establishing IKE_SA failed, peer not responding

No gateway, usando tcpdumppodemos ver a solicitação vinda do cliente, mas o gateway não responde

20:32:48.050763 eno2np1 In  IP <REDACTED>.isakmp > <REDACTED>.maas.isakmp: isakmp: parent_sa ikev2_init[I]
20:32:48.050763 bond0 In  IP <REDACTED>.isakmp > <REDACTED>.maas.isakmp: isakmp: parent_sa ikev2_init[I]
20:32:48.050763 bond0.7 In  IP <REDACTED>.isakmp > <REDACTED>.maas.isakmp: isakmp: parent_sa ikev2_init[I]
20:33:01.011245 eno2np1 In  IP <REDACTED>.isakmp > <REDACTED>.maas.isakmp: isakmp: parent_sa ikev2_init[I]
20:33:01.011245 bond0 In  IP <REDACTED>.isakmp > <REDACTED>.maas.isakmp: isakmp: parent_sa ikev2_init[I]
20:33:01.011245 bond0.7 In  IP <REDACTED>.isakmp > <REDACTED>.maas.isakmp: isakmp: parent_sa ikev2_init[I]
20:33:24.339522 eno2np1 In  IP <REDACTED>.isakmp > <REDACTED>.maas.isakmp: isakmp: parent_sa ikev2_init[I]
20:33:24.339522 bond0 In  IP <REDACTED>.isakmp > <REDACTED>.maas.isakmp: isakmp: parent_sa ikev2_init[I]
20:33:24.339522 bond0.7 In  IP <REDACTED>.isakmp > <REDACTED>.maas.isakmp: isakmp: parent_sa ikev2_init[I]
20:34:06.329906 eno2np1 In  IP <REDACTED>.isakmp > <REDACTED>.maas.isakmp: isakmp: parent_sa ikev2_init[I]
20:34:06.329906 bond0 In  IP <REDACTED>.isakmp > <REDACTED>.maas.isakmp: isakmp: parent_sa ikev2_init[I]
20:34:06.329906 bond0.7 In  IP <REDACTED>.isakmp > <REDACTED>.maas.isakmp: isakmp: parent_sa ikev2_init[I]