Xen users - Jun 2008 - odd behavior with network-bridge and ip aliases on domU:s

Hi!

I''m experiencing odd behavior of Linux domU:s that are running on 
bridged ethernet and using ip aliases. I''ve been able to rule out 
everything, including multiple bridges on domU:s to just adding ip aliases.

When I do "ifconfig eth0:1 xx.xxx.xxx.xxx" on the domU, it stops 
respondig over ethernet, on the original address also which is specified 
in the .cfg. Is there a way to specify both/all addresses in the .cfg? 
Or is there a "best practice" that I should follow? :)

I''m using the xen-hypervisor-3.0.3-1-amd64 Debian Etch package.

Thanks in advance

Markus

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> I''m experiencing odd behavior of Linux domU:s that are running on
> bridged ethernet and using ip aliases. I''ve been able to rule out
> everything, including multiple bridges on domU:s to just adding ip
> aliases.
> 
> When I do "ifconfig eth0:1 xx.xxx.xxx.xxx" on the domU, it stops
> respondig over ethernet, on the original address also which is
specified
> in the .cfg. Is there a way to specify both/all addresses in the .cfg?
> Or is there a "best practice" that I should follow? :)
I don''t think interface aliases are really supported anymore.

You can add a new ip address to an interface by just doing:

ip addr add xxx.xxx.xxx.xxx/yyy dev iface

eg

ip addr add 11.22.33.44/24 dev eth0

and often you don''t actually need the secondary addresses on the
interface so you can just add them to lo instead.

Under Debian you can add the command to /etc/network/interfaces, eg:

"
auto xen-br0
iface xen-br0 inet static
bridge_ports eth0
 bridge_maxwait 0
 # primary address
 address 11.22.33.40
 netmask 255.255.255.0
 gateway 192.168.200.254
 # secondary address
 up /sbin/ip addr add 11.22.33.44/24 dev $IFACE || true
"

if you add them to lo instead, then you''ll need a
''down'' too, eg

"
auto lo
iface lo inet loopback
 up /sbin/ip addr add 11.22.33.44/24 dev $IFACE || true
 down /sbin/ip addr del 11.22.33.44/24 dev $IFACE || true
"

I normally put the ''|| true'' at the end so that a failure to
add or
remove an address doesn''t prevent the interface coming up or going
down.

The reason I add addresses to lo instead of the interface is that the
routing daemons I use announce using all IP addresses on an interface
which looks messy.

James


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