434

Port 434/tcp is registered with IANA as mobileip-agent with the description "MobileIP-Agent" and blank assignee, contact, dates, and reference fields (dual-registered on TCP and UDP); its neighbor 435 is mobilip-mn ("MobilIP-MN," the mobile node). Its purpose is home-agent and foreign-agent registration signaling for Mobile IPv4, which lets a mobile node keep a stable home IP address while roaming. Mobile IP is defined across RFC 2002 (1996), RFC 3344 (2002), and RFC 5944 (2010); the IANA Mobile IPv4 registry notes that Mobile IP defines a set of control messages sent with UDP or TCP using well-known port number 434, carrying registration and registration-reply and related message types, and in practice it runs over UDP. The technology is largely superseded by Mobile IPv6 and modern mobility mechanisms. The IANA reference field is blank. Security-wise the port is niche and Mobile IPv4 is mostly historical; older Mobile IP had registration-spoofing and authentication concerns, but there is minimal modern footprint or attacker interest. For an analyst, an open 434 is a rare, near-obsolete finding that should be investigated as a legacy mobility agent or an anomalous service.

IANA assignment

mobileip-agent — "MobileIP-Agent"; reference (blank — no RFC cited in IANA registry); assignee blank; dual-registered 434/tcp + 434/udp (UDP is the operational transport) [IANA-assigned] — IANA Service Name and Transport Protocol Port Number Registry

Range class

well-known (0–1023)

Prevalence

extremely low; nmap-services open-frequency ~0.000013 (de-facto) [Well-established] — nmap-services file

Related ports

435 (mobilip-mn — the mobile node)

Primary use

Mobile IPv4 home-agent/foreign-agent registration signaling (RFC 3344/5944)

Other/unofficial uses

none today [Well-established]

Security implications

niche; Mobile IPv4 mostly historical; old Mobile IP registration-spoofing/auth concerns; minimal modern footprint [Well-established]

Typically seen on

historical Mobile IP home/foreign agents

Analyst note

An open 434 is a rare, near-obsolete finding; investigate as a legacy mobility agent or anomalous service.

Port 434/udp carries Mobile IP registration signaling under the IANA name mobileip-agent; it is a niche, largely obsolete protocol that should stay restricted to trusted mobility infrastructure rather than sit exposed on the public internet. IANA's Service Name and Transport Protocol Port Number Registry lists 434/udp as mobileip-agent ("MobileIP-Agent") with both the assignee and Reference columns blank — no RFC is cited in the registry itself — and the same name is dual-registered on 434/tcp.

The underlying protocol is IETF Mobile IP: RFC 2002 (1996), later obsoleted by RFC 3344 (2002). A Mobile Node roaming onto a foreign network sends Registration Request and Registration Reply messages to its Home Agent, often via a Foreign Agent, to keep a stable home address while moving between networks. Agent Advertisement itself piggybacks on ICMP Router Advertisement rather than this port — the registration exchange is what actually flows over UDP/434.

Nmap-services scan data puts 434/udp's open-frequency at 0.002257 (roughly 0.23% of scanned hosts), against a near-zero 0.000013 for the dual-registered 434/tcp — confirming UDP as the protocol's real operational transport. No mainstream consumer or commercial software was found generating traffic on this port as of an August 2026 search; the one concrete sighting is mkiol/MobileIP, an open-source Linux implementation that documents launching its Home Agent service on UDP 434.

IANA assignment

mobileip-agent — "MobileIP-Agent"; reference (blank — no RFC cited in IANA registry); assignee (blank); dual-registered 434/tcp + 434/udp [Confirmed] — the IANA Service Name and Transport Protocol Port Number Registry mobileip-agent 434/udp

Range class

well-known (0–1023) [Confirmed] — IANA Service Name and Transport Protocol Port Number Registry

Prevalence

nmap-services open-frequency 434/udp = 0.002257 (~0.23%); the dual-registered 434/tcp figure is 0.000013 (~0.001%), confirming UDP as the operational transport [Confirmed] — this site's own tooling

Related ports

434/tcp (dual registration, same mobileip-agent name); 435/tcp+udp (mobilip-mn — the mobile-node counterpart) [Confirmed] — the IANA Service Name and Transport Protocol Port Number Registry mobileip-agent 434/tcp; the IANA Service Name and Transport Protocol Port Number Registry mobilip-mn 435/udp

Primary use

IETF Mobile IP (RFC 2002, 1996; obsoleted by RFC 3344, 2002) registration signaling — a Mobile Node sends Registration Request/Reply to its Home Agent/Foreign Agent to keep a stable home address while roaming; Agent Advertisement itself rides on ICMP, not this port

Other/unofficial uses

mkiol/MobileIP — an open-source Linux Mobile IP implementation (GitHub) documented running its Home Agent service on this port; no mainstream consumer or commercial software found using 434/udp as of an August 2026 search

Security implications

no CVE or malware/backdoor association confirmed as of an August 2026 search; SANS ISC shows only low, sporadic scanning activity; auditmypc.com's UDP-434 page gives an explicit negative on IDS/malware indicators

Typically seen on

legacy or niche Mobile IP home/foreign agents; otherwise a rare, largely obsolete finding if seen open

Analyst note

A responsive 434/udp today is a rare, largely obsolete finding — investigate as a legacy Mobile IP agent, a misconfiguration, or a possible decoy/backdoor rather than assuming routine traffic.