  Multipath routing is useful for networks to achieve load sharing among
multiple routing paths. Multipath BGP (MBGP) is a technique to realize
inter-domain multipath routing by enabling a BGP router to install multiple
equally-good routes to a destination prefix. Most of previous works did not
distinguish between intra-domain and inter-domain multipath routing. In this
paper, we present a measurement study on the deployment of M-BGP in a large
Internet service provider (ISP) network. Our method combines control-plane BGP
measurements using Looking Glasses (LG), and data-plane traceroute measurements
using RIPE Atlas. We focus on Hurricane Electric (AS6939) because it is a
global ISP that connects with hundreds of major exchange points and exchanges
IP traffic with thousands of different networks. And more importantly, we find
that this ISP has by far the largest number of M-BGP deployments among
autonomous systems with LG servers. Specifically, Hurricane Electric has
deployed M-BGP with 512 of its peering ASes at 58 PoPs around the world,
including many top ASes and content providers. We also observe that most of its
M-BGP deployments involve IXP interconnections. Our work provides insights into
the latest deployment of M-BGP in a major ISP network and it highlights the
characteristics and effectiveness of M-BGP as a means to realize load sharing.
