Robtex

Up: 199.255.120.0/21
Can't show all results, try to descend to a more specific CIDR
Down left: 199.255.120.0/23
Down right: 199.255.122.0/23
(Some of the IP numbers are capped at 3 entries)

IP	Type	Hostname
199.255.120.121	A	mailer.ringcentral.com
199.255.120.122	A	mailer1.ringcentral.com
199.255.120.133	A	webphone-sip.ringcentral.com
199.255.120.135	A+PTR	media.ringcentral.com
199.255.120.142	A	v.ringcentral.com
199.255.120.146	A	sip.ringcentral.com
199.255.120.162	A+PTR	sip111.ringcentral.com
199.255.120.163	A+PTR	sip211.ringcentral.com
199.255.120.164	A+PTR	sip112.ringcentral.com
199.255.120.165	A	sip212.ringcentral.com
199.255.120.166	A+PTR	sip113.ringcentral.com
199.255.120.167	A+PTR	sip213.ringcentral.com
199.255.120.168	A+PTR	sip114.ringcentral.com
199.255.120.169	A+PTR	sip214.ringcentral.com
199.255.120.170	A+PTR	sip115.ringcentral.com
199.255.120.171	A+PTR	sip215.ringcentral.com
199.255.120.172	A+PTR	sip116.ringcentral.com
199.255.120.173	A+PTR	sip216.ringcentral.com
199.255.120.173	A	sip123-141.ringcentral.com
199.255.120.176	PTR	sip.ringcentral.com
199.255.120.176	A	sip10.ringcentral.com
199.255.120.177	A+PTR	sip20.ringcentral.com
199.255.120.181	A+PTR	sip132-141.ringcentral.com
199.255.120.182	A+PTR	sip311.ringcentral.com
199.255.120.182	A	sip311.ringcentral.co.uk
199.255.120.183	A+PTR	sip411.ringcentral.com
199.255.120.184	A+PTR	linetest.ringcentral.co.uk
199.255.120.185	A	sip118.ringcentral.com
199.255.120.186	A	sip218.ringcentral.com
199.255.120.188	PTR	sip123.ringcentral.com
199.255.120.190	A	sip119.ringcentral.com
199.255.120.191	A	sip219.ringcentral.com
199.255.120.195	PTR	sip221.ringcentral.com
199.255.120.195	A	sip120.ringcentral.com
199.255.120.196	PTR	sip222.ringcentral.com
199.255.120.196	A	sip220.ringcentral.com
199.255.120.197	A+PTR	sip381-131.ringcentral.com
199.255.120.199	A+PTR	sip225.ringcentral.com
199.255.120.200	A	sip121.ringcentral.com
199.255.120.201	A	sip412-101.ringcentral.biz
199.255.120.204	A	sip221.ringcentral.com
199.255.120.210	A+PTR	platform.ringcentral.com
199.255.120.212	A+PTR	sip122.ringcentral.com
199.255.120.214	A	sip222.ringcentral.com
199.255.120.214	A	sip10.ringcentral.biz
199.255.120.216	A+PTR	cd.ringcentral.com
199.255.120.218	A+PTR	login-telus.ringcentral.com
199.255.120.219	A	sip421-101.ringcentral.biz
199.255.120.223	A+PTR	sip113-151.ringcentral.com
199.255.120.229	A	yp.ringcentral.co.uk
199.255.120.230	A	api.ringcentral.co.uk
199.255.120.231	A	service.ringcentral.co.uk
199.255.120.233	PTR	sso.ringcentral.com
199.255.120.234	A	yp.ringcentral.com
199.255.120.235	A	service-telus.ringcentral.com
199.255.120.237	A+PTR	pp.ringcentral.com
199.255.120.239	A	cp.ringcentral.com
199.255.120.244	A	sip511.ringcentral.com
199.255.120.249	A+PTR	api.ringcentral.com
199.255.120.249	A	api-spold.ringcentral.com
199.255.120.250	A+PTR	service.ringcentral.com
199.255.120.250	A	download.ringcentral.com
199.255.120.251	PTR	agentconnect.ringcentral.com
199.255.120.252	A+PTR	sync.ringcentral.com
199.255.120.253	A	japi.ringcentral.com
199.255.122.2	PTR	vlan-310.sjc01-c01-vsw01.ringcentral.com
199.255.122.30	PTR	ringcentral.com
199.255.122.30	PTR	1-800-numbers.ringcentral.com
199.255.122.30	PTR	800-number.ringcentral.com
199.255.122.35	PTR	api.ringcentral.com
199.255.122.38	A+PTR	affiliate.ringcentral.com
199.255.122.38	PTR	affiliates.ringcentral.com
199.255.122.38	A+PTR	origin101-test.ringcentral.com
199.255.122.42	A+PTR	sjc01rel02.ringcentral.com
199.255.122.43	A+PTR	sjc01rel03.ringcentral.com
199.255.122.44	A+PTR	sjc01rel04.ringcentral.com
199.255.122.68	PTR	cloudfax.ringcentral.com
199.255.122.68	PTR	faxout.ringcentral.com
199.255.122.68	A	analytics.ringcentral.com
199.255.122.78	A	sp-download.ringcentral.com
199.255.122.78	A	crr.ringcentral.com
199.255.122.100	A	ftp.ringcentral.com
199.255.122.103	A	service-officeathand.att.com
199.255.122.103	A	ws03a.ringcentral.com
199.255.122.105	PTR	support.ringcentral.com
199.255.122.105	A+PTR	tracking.ringcentral.com
199.255.122.132	PTR	e1-1.sjc01-c01-fwl01.ringcentral.com
199.255.122.148	A	sjc01-z01-zwc01.ringcentral.com
199.255.122.151	A+PTR	sjc01-z01-zmr51.ringcentral.com
199.255.122.163	A	sjc01-z01-zwc02.ringcentral.com
199.255.122.188	A	sjc01-z01-zmr27.ringcentral.com
199.255.122.195	A	sjc01-z01-zmr31.ringcentral.com
199.255.122.196	A	sjc01-z01-zmr33.ringcentral.com
199.255.122.198	A	sjc01-z01-zmr35.ringcentral.com
199.255.122.207	A	sjc01-z01-zmr37.ringcentral.com
199.255.122.212	A	sjc01-z01-zmr41.ringcentral.com
199.255.122.215	A+PTR	sjc01-z01-zmr66.ringcentral.com
199.255.122.218	A	sjc01-z01-zmr47.ringcentral.com
199.255.122.221	A	ntp1.ringcentral.com
199.255.122.222	A	ntp1.ringcentral.com
199.255.122.228	A+PTR	sjc01-z01-zmr09.ringcentral.com
199.255.122.241	A+PTR	sjc01-z01-zmr93-1.ringcentral.com
199.255.122.245	A	sjc01-z01-zmr05.ringcentral.com
199.255.122.246	A+PTR	sjc01-z01-zmr96-1.ringcentral.com
199.255.122.249	A	sjc01-z01-zmc01.ringcentral.com
199.255.122.250	A	sjc01-z01-zmc02.ringcentral.com
199.255.122.251	A+PTR	sjc01-z01-zmr22.ringcentral.com
199.255.122.253	A+PTR	e1-1.sjc01-c01-fwl01.ringcentral.com
199.255.123.123	PTR	sip.ringcentral.com
199.255.123.123	PTR	sip10.ringcentral.com
199.255.123.123	PTR	sip.up.ringcentral.com