終于把dynamips上面劃vlan給搞定了，屢試不爽，還能在模擬的三層交換機上起trunk和svi。

先是在R7，原來的fr交換機上加一塊PA-8E的板子，然后分組橋接，配置上BVI和多個橋接組。

想trunk也不難，vlan iD也可以訂制。

IF:interface_name:netio_type[:netio_parameters]

1) Configuring an Access Port

syntax: ACCESS:interface_name:vlan_id

2) Configuration a 802.1Q Trunk Port

syntax: DOT1Q:interface_name:native_vlan

The native VLAN is not tagged. On Cisco devices, by default the native VLAN
is VLAN 1.

Example of configuration file:

IF:E0:udp:10000:127.0.0.1:10001
IF:E1:udp:10002:127.0.0.1:10003
IF:E2:gen_eth:eth0

DOT1Q:E0:1
ACCESS:E1:4
DOT1Q:E2:1
這樣，我R7也成了一臺三層設備。top的靈活程度又提高了。

16 Ethernet interfaces
2 FastEthernet interfaces
8 Serial interfaces
125K bytes of NVRAM.