# CARP over lagg(4)



## brtkz (Nov 4, 2009)

I have Dell R200 server with four em(4) interfaces (Intel 1000 PT Dual Port on PCIe) with FreeBSD 8.0 RC1. I configure lagg(4) with two em(4) interfaces. Next I try to add CARP to lagg0 but it goes to MASTER and next to BACKUP state and again to MASTER etc (repeats every 5 second). Even if it is only one machine in network. CARP configured on physical interface works fine.

How should I configure carp interface over lagg? I try the same configuration on OpenBSD (with trunk and carp) and it works well. 

Today I try RC2 but it can't create carp0 interface at all.


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## phoenix (Nov 5, 2009)

Which laggproto are you using?  I believe carp-on-lagg only works for lacp, but I could be mistaken.


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## brtkz (Nov 5, 2009)

I wanted to use 'roundrobin', but it seems receiving transmited packet from one card by second one in lagg(4). On OpenBSD trunk(4) configured with roundrobin and carp discards duplicated packet and works very well.

I solved this problem with 'failover' mode for lagg device. My switches unfortunately do not support LACP.


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## dennylin93 (Nov 5, 2009)

From the Handbook:


> Round-robin
> 
> Distributes outgoing traffic using a round-robin scheduler through all active ports and accepts incoming traffic from any active port. This mode violates Ethernet Frame ordering and should be used with caution.



Perhaps this is the problem.


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