Ono što je tebi potrebno je statički NAT. Npr:
Adresa na serijskom interfejsu je: 1.2.3.4/30
LAN koristi: 192.168.1.0/24
MySQL server: 192.168.1.1
MySQL port: 3306
Code:
interface Serial0
ip address 1.2.3.4 255.255.255.252
ip nat outside
!
interface Ethernet0
ip address 192.168.1.254 255.255.255.0
ip nat inside
!
ip nat source static tcp 192.168.1.1 3306 interface Serial 0 3306
Marko.