ASN AS18731 is an Autonomous System Number used to identify a network for BGP internet routing.

Who manages ASN AS18731?

AS18731 is listed under Cityside Fiber.

What do peers, upstreams, and downstreams mean in ASN data?

Peers are lateral network interconnections, upstreams are transit providers, and downstreams are customer networks receiving connectivity.

What are routes and IP ranges for an ASN?

Routes and IP ranges are the network prefixes announced by the ASN on the internet and show the address space it originates.

Why is WHOIS data shown for an ASN?

WHOIS data provides registration and contact context for ASN ownership, administration, and operational reference.

How can I access the full ASN tables?

The page shows a preview of large ASN datasets. Use the page controls to load more rows, and upgrade to a paid plan for complete access.

AS18731 Cityside Fiber | IPGeolocation.io

ASN Lookup Tool

Cityside Fiber citysidefiber.com

US 3 Routes

AS Data

AS18731

AS18731 – Cityside Fiber

AS Number	18731
AS Name	CITYSIDE-01
Organization	Cityside Fiber(cnl-178)
Country	US
Website	citysidefiber.com
Number of IPv4 Routes	2
Number of IPv6 Routes	1
ASN type	ISP
Registry	ARIN
Date Allocated	2023-10-12

ASN Intelligence API for production workflows

Use ASN data for AS18731 in automation: routing intelligence, peering analysis, ownership checks, and network observability.

Access complete peers, upstreams, downstreams, routes, WHOIS, and contact intelligence via our API. Learn more

Get ASN API Key ASN API Docs

IP Ranges

Route	Origin	Origin Name	ISP	# IPs
2607:73c0:100::/48	AS18731	Cityside Fiber	Cityside Fiber	~1×10²⁴
23.164.40.0/24	AS18731	Cityside Fiber	Cityside Fiber	256
128.177.138.0/24	AS18731	Cityside Fiber	Cityside Networks	256

Raw Whois Response

#
# ARIN WHOIS data and services are subject to the Terms of Use
# available at: https://www.arin.net/resources/registry/whois/tou/
#
# If you see inaccuracies in the results, please report at
# https://www.arin.net/resources/registry/whois/inaccuracy_reporting/
#
# Copyright 1997-2026, American Registry for Internet Numbers, Ltd.
#


ASNumber:       18731
ASName:         CITYSIDE-01
ASHandle:       AS18731
RegDate:        2023-10-12
Updated:        2023-10-12
Comment:        http://www.citysidefiber.com
Comment:        NOC hours 
Comment:        07:00 to 16:00 PST    
Ref:            https://rdap.arin.net/registry/autnum/18731


OrgName:        Cityside Fiber
OrgId:          CNL-178
Address:        100 Spectrum Center Dr suite 500
City:           Irvine
StateProv:      CA
PostalCode:     92618
Country:        US
RegDate:        2023-10-05
Updated:        2025-05-12
Ref:            https://rdap.arin.net/registry/entity/CNL-178


OrgAbuseHandle: SIMON405-ARIN
OrgAbuseName:   Simon, Jacob 
OrgAbusePhone:  +1-727-599-9912 
OrgAbuseEmail:  jake.simon@citysidenetworks.com
OrgAbuseRef:    https://rdap.arin.net/registry/entity/SIMON405-ARIN

OrgTechHandle: SIMON405-ARIN
OrgTechName:   Simon, Jacob 
OrgTechPhone:  +1-727-599-9912 
OrgTechEmail:  jake.simon@citysidenetworks.com
OrgTechRef:    https://rdap.arin.net/registry/entity/SIMON405-ARIN

OrgDNSHandle: MOORE1860-ARIN
OrgDNSName:   Moore, Logan 
OrgDNSPhone:  +1-309-267-8574 
OrgDNSEmail:  logan.moore@citysidefiber.com
OrgDNSRef:    https://rdap.arin.net/registry/entity/MOORE1860-ARIN

OrgNOCHandle: PELAG1-ARIN
OrgNOCName:   Pelagio, Raul 
OrgNOCPhone:  +1-877-914-2489 
OrgNOCEmail:  noc@citysidefiber.com
OrgNOCRef:    https://rdap.arin.net/registry/entity/PELAG1-ARIN

OrgNOCHandle: SIMON405-ARIN
OrgNOCName:   Simon, Jacob 
OrgNOCPhone:  +1-727-599-9912 
OrgNOCEmail:  jake.simon@citysidenetworks.com
OrgNOCRef:    https://rdap.arin.net/registry/entity/SIMON405-ARIN

OrgDNSHandle: SIMON405-ARIN
OrgDNSName:   Simon, Jacob 
OrgDNSPhone:  +1-727-599-9912 
OrgDNSEmail:  jake.simon@citysidenetworks.com
OrgDNSRef:    https://rdap.arin.net/registry/entity/SIMON405-ARIN

OrgTechHandle: MOORE1860-ARIN
OrgTechName:   Moore, Logan 
OrgTechPhone:  +1-309-267-8574 
OrgTechEmail:  logan.moore@citysidefiber.com
OrgTechRef:    https://rdap.arin.net/registry/entity/MOORE1860-ARIN

OrgRoutingHandle: MOORE1860-ARIN
OrgRoutingName:   Moore, Logan 
OrgRoutingPhone:  +1-309-267-8574 
OrgRoutingEmail:  logan.moore@citysidefiber.com
OrgRoutingRef:    https://rdap.arin.net/registry/entity/MOORE1860-ARIN

OrgAbuseHandle: PELAG1-ARIN
OrgAbuseName:   Pelagio, Raul 
OrgAbusePhone:  +1-877-914-2489 
OrgAbuseEmail:  noc@citysidefiber.com
OrgAbuseRef:    https://rdap.arin.net/registry/entity/PELAG1-ARIN

OrgRoutingHandle: SIMON405-ARIN
OrgRoutingName:   Simon, Jacob 
OrgRoutingPhone:  +1-727-599-9912 
OrgRoutingEmail:  jake.simon@citysidenetworks.com
OrgRoutingRef:    https://rdap.arin.net/registry/entity/SIMON405-ARIN


#
# ARIN WHOIS data and services are subject to the Terms of Use
# available at: https://www.arin.net/resources/registry/whois/tou/
#
# If you see inaccuracies in the results, please report at
# https://www.arin.net/resources/registry/whois/inaccuracy_reporting/
#
# Copyright 1997-2026, American Registry for Internet Numbers, Ltd.
#

Parsed Whois Response

Peers

AS Number	Description	Country
AS3549	Level 3 Communications, Inc. (GBLX)	US
AS3356	Level 3 Parent, LLC	US
AS6461	Zayo Bandwidth	US

Upstreams

AS Number	Description	Country
AS3356	Level 3 Parent, LLC	US
AS6461	Zayo Bandwidth	US