For CDN Static services you can set Secondary Origin Domains for failover of the Origin Domain.
Please refer to Understanding difference between origin and CDN content for more details on the Origin Domain.
You can set up to two Secondary Origin Domains and have 3 Origin Domains (Origin Domain plus Secondary Origin Domains).
Please note that for services with Secondary Origin Domains we require both Origin Domain and all Secondary Origin Domains to be IP addresses. Also please note that if one of the origins is down, the CDN service will fail over to running origins. However, in the case of all origins are up, the CDN service will fetch your content from all the origin IP addresses.