# Network stack b0rked after (lots of) arp changes



## frijsdijk (Apr 1, 2011)

Hi,

We (hosting provider) are in the process of implementing ipv6 in our network (yay). Yesterday one of the final steps in configuring and updating our core routers were taken, which did not go entirely as planned. As a result, the default gateway mac addresses for all our machines changed about 800 times in a time span of about 4 minutes.

Here's a small piece of the logging:


```
Mar 31 18:36:03 srv01 kernel: arp: 87.x.x.1 moved from 00:00:0c:07:ac:3d to 00:00:0c:9f:f0:3d on bge0
Mar 31 18:36:04 srv01 kernel: arp: 87.x.x.1 moved from 00:00:0c:9f:f0:3d to 00:00:0c:07:ac:3d on bge0
Mar 31 18:36:04 srv01 kernel: arp: 87.x.x.1 moved from 00:00:0c:07:ac:3d to 00:00:0c:9f:f0:3d on bge0
Mar 31 18:36:04 srv01 kernel: arp: 87.x.x.1 moved from 00:00:0c:9f:f0:3d to 00:00:0c:07:ac:3d on bge0
Mar 31 18:36:05 srv01 kernel: arp: 87.x.x.1 moved from 00:00:0c:07:ac:3d to 00:00:0c:9f:f0:3d on bge0
Mar 31 18:36:05 srv01 kernel: arp: 87.x.x.1 moved from 00:00:0c:9f:f0:3d to 00:00:0c:07:ac:3d on bge0
```

The result of that, is that loads of FreeBSD machines (6.x, 7.x and 8.x) developed serious network issues, mainly being no or slow traffic between other (FreeBSD) machine accross different VLAN's in our own network.

First thing that comes to mind is the network itself, but all Linux machines (Ubuntu, Red Hat and CentOS) had no issues at all. Only BSD.

An *arp -ad* on both machines where problems occured, didn't solve anything. What worked better was */etc/rc.d/netif restart* and a */etc/rc.d/routing restart*. Some machines even had to be rebooted in order to get networking back to normal.

This almost sounds like a bug in the network stack in BSD, but I can not imagine that I'm right. The BSD networking stack is considered to be one of the best..

Any ideas anyone?


-- Frederique


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## aragon (Apr 1, 2011)

I really think you should post this to the freebsd-net@ list too...


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## frijsdijk (Apr 1, 2011)

Done!


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