# Dummynet Strange Behaviour



## MartynH (Feb 13, 2013)

Hi *a*ll,

Thanks in advance for your help with this one. I have a VMWare FreeBSD v9 server, with 3 network interfaces:

em0 - management - DHCP
em1 - 'lab' network - No IP4 or 6
em2 - 'test' network - No IP4 or 6

I have a bridge configured from em1 to em2, and am attempting to use IPFW/Dummynet to pipe the traffic passing over this bridge so that the 'test' side of the network can simulate remote clients connecting to servers on the 'lab' side of the network in a variety of network conditions. 

I am attempting to test this installation by setting up a continuous `ping -t` from a Windows 7 client on the 'test' side of the network to a machine on the 'lab' side of the network.

With no delay or bandwidth throttling the bridge passes the pings correctly. 

The problem comes when I increase the delay: 


```
ipfw pipe 1 config delay 10ms
```

This breaks all network traffic across the bridge. Even adding, say, 5 ms delay doesn't appear to have any effect until it hits 10ms when it breaks the bridge. Am I missing something?

Interestingly if I add an additional pipe relating to em0 and ping google.com the config delay commands work brilliantly.

My rc.conf:


```
hostname="SPDemo-NetSimulator"
keymap="uk.iso.kbd"
ifconfig_em0="DHCP"
cloned_interfaces="bridge0"
ifconfig_bridge0="addm em1 addm em2 up"
ifconfig_em1="up"
ifconfig_em2="up"
sshd_enable="YES"
ntpd_enable="YES"
firewall_enable="YES"
firewall_type="/etc/fw.conf"
dummynet_enable="YES"
```

My `ipfw list`:

```
00051 add pipe 1 ip from any to any recv em1
00052 add pipe 1 ip from any to any recv em2
00053 add allow ip from any to any
65535 deny ip from any to any
```


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## HackerNumber9 (Mar 7, 2013)

Are you sure this is supposed to work with a VMWARE installation?


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