and "oh my...", I even remember having read that you're using KVM... and yes of course, my reply is about Xen

How do you issue the migration request? Assuming it is via "virsh", it'S man page states:

When migrateuri is not specified, libvirt will automatically determine the hypervisor specific URI. Some hypervisors, including QEMU, have an optional "migration_host" configuration parameter (useful when the host has multiple network interfaces). If
this is unspecified, libvirt determines a name by looking up the target host's configured hostname.

There are a few scenarios where specifying migrateuri may help:

The configured hostname is incorrect, or DNS is broken. If a host has a hostname which will not resolve to match one of its public IP addresses, then libvirt will generate an incorrect URI. In this case migrateuri should be explicitly specified,
using an IP address, or a correct hostname.

The host has multiple network interfaces. If a host has multiple network interfaces, it might be desirable for the migration data stream to be sent over a specific interface for either security or performance reasons. In this case migrateuri
should be explicitly specified, using an IP address associated with the network to be used.

The firewall restricts what ports are available. When libvirt generates a migration URI, it will pick a port number using hypervisor specific rules. Some hypervisors only require a single port to be open in the firewalls, while others require a
whole range of port numbers. In the latter case migrateuri might be specified to choose a specific port number outside the default range in order to comply with local firewall policies.

See <http://libvirt.org/migration.html#uris> for more details on migration URIs.
So while my original comments were for "xm", they semantically apply to your situation: Whereever you define the target host for the migration request, make sure to specify it's 10G interface, likely via an interface-specific DNS name or via IP.

I've not used KVM on SLES11SP4 yet, but on later systems, there's /etc/libvirt/qemu.conf, where you'll again find similar parameters to the ones I originally described for Xen:

# Override the listen address for all incoming migrations. Defaults to
#, or :: if both host and qemu are capable of IPv6.
#migration_address = ""

# The default hostname or IP address which will be used by a migration
# source for transferring migration data to this host.  The migration
# source has to be able to resolve this hostname and connect to it so
# setting "localhost" will not work.  By default, the host's configured
# hostname is used.
#migration_host = "host.example.com"

# Override the port range used for incoming migrations.
# Minimum must be greater than 0, however when QEMU is not running as root,
# setting the minimum to be lower than 1024 will not work.
# Maximum must not be greater than 65535.
#migration_port_min = 49152
#migration_port_max = 49215
It's "migration_address" that is typically set to "listen on all hosts", which you might use to limit migrations to 10G interfaces only, and you'll likely have to give the 10G interface a unique DNS name so that originating servers can reach the KVM target server's 10G interface - I'd put that DNS name in "migration_host".

I hope this time my coffee level was high enough, sorry for the misleading initial response.