[c-nsp] Flapping & Linux bonding

[Colin Whittaker]

H there,

We do this for approx 25 servers, currently on a pair of 6500s but
before that we used 4ks. 

That message is normal enough if you only see it when the machine starts
up. If it appears more frequently you have a problem which is causing
the active interface to change.
Only thing to be aware of is if using portsecurity is that the
switchport can see the nic's original MAC prior to the bond driver
overriding the MAC.
Below is our config from a machine running debian. We use both carrier 
detection and arp checking to detect link failure.
The ipv6 lines at the end are to prevent a problem with the bond driver
where all your servers endup with the same eui-64 link local address.
We use static ipv6 addresses on the servers and so don't need to fix the
global eui-64 addresses.

Regards,

Colin

auto bond0
iface bond0 inet static
        address 193.1.219.90
        netmask 255.255.255.128
        network 193.1.219.0
        broadcast 193.1.219.127
        gateway 193.1.219.1
        pre-up modprobe bonding mode=active-backup use_carrier=1 arp_interval=200 arp_ip_target=193.1.219.1
        pre-up ip link set dev eth0 up
        pre-up ip link set dev eth1 up
        up ifenslave bond0 eth0
        up ifenslave bond0 eth1
        post-down ip link set dev eth0 down
        post-down ip link set dev eth1 down
        up ip addr del fe80::200:ff:fe00:0/64 dev bond0
        up ip addr add `ip addr show dev eth1 scope link | grep inet6 | awk '{ print $2 }'` dev bond0

iface bond0 inet6 static
        address 2001:770:18:2::90
        netmask 64


On Tue, May 31, 2005 at 04:10:18PM +0200, Xavier wrote:
> Hi *,
> 
> Context: a Linux server connected to two Catalyst 4506.
> On the Linux box, eth0 and eth1 are bonded to bond0.
> 
> On the first switch (first to be connected to the Linux), I got:
> 
> %C4K_EBM-4-HOSTFLAPPING: Host xx:xx:xx:xx:xx:xx in VLAN 200 is flapping between port Gi2/12 and port Gi1/1
> (Gi1/1 is connected to the second switch - trunk)
> 
> Any idea?
> 
> Xavier
> --
> Speak softly and carry a cellular phone.
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-- 
Colin Whittaker    colin.whittaker at heanet.ie    Tel: +353 1 6609040
HEAnet NOC         noc at heanet.ie                iNOC-DBA:  1213*752