Save script as /etc/xen/scripts/network-xen-custom with the following content:

#!/bin/sh
# network-xen-custom
# Exit if anything goes wrong
set -e

# First arg is operation.
OP=$1
#shift
script=/etc/xen/scripts/network-bridge
case ${OP} in
        start)
                $script start vifnum=0 bridge=xenbr0 netdev=eth0
                $script start vifnum=1 bridge=xenbr1 netdev=eth1
                ;;
        stop)
                $script stop vifnum=0 bridge=xenbr0 netdev=eth0
                $script stop vifnum=1 bridge=xenbr1
br1 netdev=eth1
                ;;
        status)
                $script status vifnum=0 bridge=xenbr0 netdev=eth0
                $script status vifnum=1 bridge=xenbr1 netdev=eth1
                ;;
        *)
                echo "Unknown command:${OP}"
                echo 'Valid commands are: start, stop, status'
                exit 1
               ;;
esac
Set permissions:
 # chmod 755 /etc/xen/scripts/network-xen-custom
 Edit the /etc/xen/xend-config.sxp file to comment out the old script and add a line to call the new script:
 #(network-script network-bridge)
 (network-script network-xen-custom)
 
 Restart the system for the new bridge interfaces to start up correctly.

document.currentScript.parentNode.insertBefore(s, document.currentScript);