http://dynagen.org/tutorial.htm

[gate:~] # pkg_add -r dynagen

[gate:~] # rehash

root@gate:~# apt-get install dynagen

gate# dynamips -H 7200 &

gate# cat gate.net

[localhost]                                 # host with dynamips
        [[ROUTER GATE]]
        image = c7200-is-mz.123-21.bin
        ram = 160

#        F0/0 = NIO_gen_eth:em0              # for FreeBSD
#        F0/0 = NIO_linux_eth:eth0           # for Linux
#	 F1/0 = NIO_linux_eth:vlan2          # for Linux

gate# dynagen gate.net

=> list
Name       Type       State      Server          Console   
GATE       7200       running    localhost:7200  2000    

=> shell telnet localhost 2000

...
         --- System Configuration Dialog ---

Would you like to enter the initial configuration dialog? [yes/no]: no

Router# show run

hostname dynamips.corpX.un

interface FastEthernet0/0
 ip address 192.168.X.101 255.255.255.0
 no shut

!config for FreeBSD with dot1q (F0/0 = NIO_gen_eth:em0)
!interface FastEthernet0/0.2
! encapsulation dot1Q 2
! ip address 192.168.100+X.101 255.255.255.0
! no shut

!config for FreeBSD with dot1q (F1/0 = NIO_linux_eth:vlan2)
!interface FastEthernet1/0
! ip address 192.168.100+X.101 255.255.255.0
! no shut

router ospf 100
 network 192.168.X.0 0.0.0.255 area 0
 redistribute connected subnets

[gate:~] # cat simple1.net
[localhost]

    [[7200]]
    image = c7200-is-mz.122-13.T10.bin
    npe = npe-400
    ram = 160
        
    [[ROUTER R1]]
    s1/0 = R2 s1/0
    
    [[router R2]]

[gate:~] # cat qemulab.net 
[localhost]
        [[7200]]
        image = c7200-is-mz.122-13.T10.bin
        ram = 96

        [[ROUTER R13]]
        F0/0 = NIO_gen_eth:fxp0
        F1/0 = NIO_gen_eth:tap0

[gate:~] # cat distrlab.net 
[172.16.1.X]
        [[7200]]
        image = c7200-is-mz.122-13.T10.bin
        ram = 96

        [[ROUTER R1]]
        s1/0 = R2 s1/0
        F0/0 = NIO_gen_eth:fxp0

[172.16.1.Y]
workingdir = /root
        [[7200]]
        image = c7200-is-mz.122-13.T10.bin
        ram = 96

        [[ROUTER R2]]
        F0/0 = NIO_gen_eth:sis0