Port 1987Cisco RSRB Priority 1

Cisco Remote Source-Route Bridging traffic for priority-1 Token Ring frame transport.

transport: tcp · udp
in transit: cleartext
assignment: official
risk: 2/10
lookups: 0

also known as tr-rsrb-p1, Remote Source-Route Bridging

Technical Details

what runs on :1987

RSRB is a Cisco-specific protocol that encapsulates Token Ring and source-route bridging traffic between configured router peers. The IANA assignment covers both TCP and UDP, with port 1987 identifying the priority-1 traffic class; related RSRB assignments include ports 1986 and 1988. RSRB carries bridged network frames rather than providing a general-purpose application service, and its traffic is not encrypted by the protocol.

Security Information

exposure of :1987

risk score

2/ 10safe

routine exposure. this port is rarely the way in on its own — keep it patched and logged and move on.

network services averages 3.6 across 704 ports — this one sits 1.6 below.

in transit

cleartext

credentials and payloads are readable by anyone on path

assignment

official

registered with iana for this service — scanners fingerprint it by number

reachable over

tcp · udp

udp is connectionless — source addresses are trivially spoofed and it is a reflection favourite

security overview

This is legacy network-infrastructure traffic and should not normally be exposed to the public Internet. An exposed RSRB endpoint could disclose or relay bridged Token Ring traffic and provide an attacker with an unexpected path into internal network segments; use peer restrictions and network filtering where the protocol is still required.

Record

iana registry entry

port: :1987
service: Cisco RSRB Priority 1
transport: TCPUDP
encryption: cleartext
assignment: iana registered
risk: 2/10safe
category: Network Services System
usage: Cisco routers use this port for priority-1 Remote Source-Route Bridging (RSRB) traffic between Token Ring networks across an IP WAN. It is a legacy infrastructure protocol and is rarely encountered on modern Internet-connected systems.
lookups: 0rank 994
added: 2026-08-24
updated: 2026-08-24
references: IANA service name registry — port 1987

Something wrong?

This record is maintained by the engineers who use port 1987. Every field on it is editable — change what's wrong, say how you know, and a reviewer publishes it, usually within a minute. Last touched 2026-08-24.

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Related Ports

all 704 in network services →

the 8 most looked-up other ports in network services — 704 ports carry that label.

port	service	proto	category	risk	views
:9080	Groove RPC	TCPUDP	Web Services	caution	70.8k
:6543	Jetnet	UDP	Network Services	caution	65.3k
:5938	TeamViewer	TCPUDP	Remote Access	caution	65.0k
:8291	Winbox MikroTik Admin	TCP	Security	caution	62.9k
:3233	WhiskerControl Protocol	TCPUDP	Network Services	caution	61.9k
:3268	Microsoft Global Catalog (GC)	TCPUDP	Security	caution	54.6k
:135	Microsoft EPMAP	TCPUDP	Security	caution	51.9k
:3128	Tatsoft Default HTTP Proxy	TCP	Web Services	caution	46.8k

risk mix of the 8 listed

caution100%

0 of 8 encrypted

Port :1987Cisco RSRB Priority 1

Technical Details

Security Information

Related Ports

Port 1987Cisco RSRB Priority 1