http://dynagen.org/tutorial.htm

[hostX:~] # pkg_add -r dynagen

[hostX:~] # rehash

root@hostX:~# apt-get install dynagen

hostX# dynamips -H 7200 &

[hostX:~] # cat router.dng

[localhost]
        [[ROUTER router.corpX.un]]
        image = c7200-is-mz.123-21.bin
        ram = 160
        npe = npe-400
        
        F1/0 = NIO_linux_eth:eth1
        F1/1 = NIO_linux_eth:eth0
        
#       F1/0 = NIO_gen_eth:em1      # For physical interface in FreeBSD
#	F1/0 = NIO_linux_eth:vlan2  # For vlan interface in Linux
#	F1/0 = NIO_gen_eth:vlan2    # For vlan interface in FreeBSD

hostX# dynagen router.dng

=> list
Name       Type       State      Server          Console   
router.corpX.un     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> enable

Router# show run

[hostX:~] # cat simple1.dng
[localhost]

    [[ROUTER R1]]
    image = c7200-is-mz.123-21.bin
    npe = npe-400
    ram = 160
        
    s1/0 = R2 s1/0
    
    [[router R2]]

[hostX:~] # cat distrlab.dng 
[172.16.1.X]
        [[ROUTER R1]]
        image = c7200-is-mz.123-21.bin
        ram = 96

        s1/0 = R2 s1/0
        F0/0 = NIO_gen_eth:fxp0

[172.16.1.Y]
workingdir = /root
        [[ROUTER R2]]
        image = c7200-is-mz.123-21.bin
        ram = 96

        F0/0 = NIO_gen_eth:sis0