When Microsoft Teams Phone Error Code 410 appears during a call, the useful clue is rarely the number alone. In Microsoft’s Direct Routing troubleshooting catalog, SIP 410 appears with three Microsoft subcodes — 531000, 531004, and 531005 — and each one points to a different repair path. Read the subcode first. Then test the path it names.
Plain-English Reading
531000 usually points to SDP negotiation that is malformed or unsupported. 531004 points to ICE connectivity checks that could not build a media path. 531005 means the media path was up and then failed.
Table of Contents
How Error Code 410 Is Used in Teams Phone
In Teams Phone Direct Routing, a failure record becomes useful when you pair two fields: the SIP response code and the Microsoft response code. Microsoft notes that these values are reported in the Teams admin center and in the Power BI Quality of Experience Report for PSTN. That pairing tells you whether the last failure should send you toward SBC signaling, media negotiation, or network path work. Misread, this code often sends teams toward the wrong fix.
What Each 410 Variant Means
Direct Routing 410 is not one issue. It is a small family of failures. Administrators often compare the pattern with other documented Microsoft Teams calling error codes to confirm whether the failure belongs to signaling, media negotiation, or network reachability. The table below keeps the first diagnosis step tied to the actual subcode, which is where many investigations become faster.
| Microsoft Subcode | What It Usually Points To | First Place to Inspect |
|---|---|---|
| 531000 | SDP offer or answer is malformed, incomplete, or unsupported | SBC trace, raw SDP body, media attributes, codec overlap, SRTP details |
| 531004 | ICE checks could not establish a media path | Firewall rules, NAT behavior, relay reachability, published IP and port access |
| 531005 | Media path existed, then broke during the call | Packet loss, jitter, round-trip delay, transient WAN issues, path changes |
531000
Think signaling and SDP first. The call fails before media becomes usable.
531004
Think path creation first. ICE cannot produce a working route for media.
531005
Think stability first. Media started, then continuity was lost.
Where to Look First Before Changing Anything
Before editing firewall rules or touching the SBC, collect the exact failed call sample. For Teams Phone, that usually means one failed call record, its CallEndReason, the six-digit CallEndSubReason, the user or resource involved, the route used, and the rough time window. Then move in this order.
- Open Call Analytics for the affected user and inspect the individual call legs.
- Check whether the same 410 subcode repeats for one site, one SBC, one trunk, or one device pool.
- Confirm whether the failure is happening on setup or after media starts flowing.
- Compare a failed call against a nearby successful call on the same route.
- Only then change network or SBC settings.
Microsoft’s Call Analytics view exists for exactly this kind of isolation work: it shows call details down to devices, networks, connectivity, and call quality, and it lets an admin inspect each leg instead of guessing from a single error number.
531000 SdpParsingFailure
With 531000, Microsoft states that the Session Description Protocol offers or answers may be malformed or unsupported. In practice, this pushes the investigation toward the raw INVITE, 183 Session Progress, and 200 OK bodies. Read the SDP itself, not just the short vendor summary. Small formatting faults matter here.
- Check that the audio media description is present and internally consistent.
- Verify that payload types, media directions, and transport details remain valid across the offer and answer.
- Confirm that crypto and SRTP-related attributes are complete and syntactically correct.
- Look for truncated lines, duplicated attributes, unsupported media sections, or attributes the peer does not accept.
- Review whether a recent SBC normalization rule changed SDP on only one direction of the call.
When this subcode appears, the fix usually comes from clean SDP generation, not from user-side resets. Often, the change is tiny — a media attribute, a transport mismatch, an offer that no longer aligns with the answer, a malformed line after an SBC update. Tiny, yes. Enough to break setup, too.
531004 IceConnectivityChecksFailed
531004 means the media path could not be established. This is the 410 variant most closely tied to reachability, firewall policy, NAT behavior, and relay access. Microsoft publishes the Direct Routing media IP ranges for Microsoft 365 and Office 365 environments as 52.112.0.0/14 and 52.120.0.0/14. Microsoft also publishes the media processor UDP/SRTP destination ranges as 3478–3481 and 49152–53247, and notes that an SBC should have at least two ports per concurrent call.
- Confirm that the SBC can send and receive media on the required published ranges.
- Check whether a firewall allows signaling yet blocks SRTP media return traffic.
- Inspect NAT translation symmetry and timeout behavior during call setup.
- Verify that the SBC is advertising reachable addresses to the far side.
- Retest from a network segment that bypasses unusual perimeter inspection rules.
There is one more pattern worth checking early: media path detours. Microsoft states that Teams media prefers the most direct available route and recommends that media traffic not pass through packet shapers, VPN servers, and similar middleboxes because they can affect media quality. If 531004 appears only on one site or one remote access pattern, this clue matters.
531005 MediaConnectivityFailure
With 531005, the call usually gets farther: media started, then continuity failed. This shifts the investigation away from pure setup syntax and toward path stability. In Call Quality Dashboard classification, an audio stream is marked poor when packet utilization is above 500 packets and at least one threshold breaks: round trip > 500 ms, packet loss rate > 0.1, or jitter > 30 ms. Those values do not prove a 531005 on their own, yet they are strong places to inspect when media drops after setup.
- Check whether the failure appears after hold, transfer, resume, or network roam events.
- Review WAN congestion windows and interface counters for the same minute as the failed call.
- Compare wired and wireless behavior for the same user group.
- Inspect jitter, packet loss, and round-trip changes before the drop.
- Test whether the issue disappears when the client avoids the VPN path.
Microsoft’s network assessment material also states that Teams network quality is measured through UDP latency, UDP jitter, and UDP packet loss. That matters because a Teams Phone call can have clean signaling while the UDP media path still degrades enough to trigger a broken session.
Media Bypass and IPv6 Notes That Matter
One detail is easy to miss during route design: IPv6 support in Teams Phone has boundaries. Microsoft states that IPv6 is supported for non-media-bypass scenarios, while media bypass with IPv6 and mixed SIP and media mode using IPv6/IPv4 are not supported. So, if Error 410 started after an addressing or routing change, do not treat the IP version as a background detail. For some paths, it is the detail.
- If the deployment uses media bypass, confirm that the call path is still inside the supported IP version model.
- If a site recently introduced IPv6, compare failing and working routes by bypass state.
- If the SBC is set to IPv6, confirm that both signaling and media follow the documented support model.
A Practical Fix Order for Admins
- Find the six-digit subcode. Without it, 410 is too broad.
- If the subcode is 531000, capture the raw SDP and compare both directions.
- If the subcode is 531004, test firewall, NAT, and reachable media addresses before changing user settings.
- If the subcode is 531005, inspect UDP quality trends and transient path changes during the call.
- Compare one failed call with one successful call on the same trunk. Differences speak faster than assumptions.
- Retest from a simpler path — no VPN, minimal inspection, stable wired access — to separate route issues from endpoint issues.
- Only after that, adjust normalization rules, media bypass design, or SBC behavior.
Error Code 410 becomes easier to fix once you stop treating it like one message. It is a routing and media diagnosis label. The subcode tells you which layer deserves your next hour.
FAQ
What does Microsoft Teams Phone Error Code 410 usually mean?
It usually means the failed call belongs to a Direct Routing scenario where the useful diagnosis depends on the Microsoft subcode paired with SIP 410. The most common paths are SDP parsing, ICE path creation, and media path failure.
Is 410 always a firewall problem?
No. 531004 often leads toward firewall, NAT, or media reachability checks, yet 531000 points toward SDP syntax or compatibility, and 531005 often needs a stability review of the live media path.
Where can I see the subcode for a failed Teams Phone call?
You usually inspect it in the Teams admin center call records or in reporting tied to PSTN quality data. The six-digit Microsoft response code matters more than the 410 alone.
Which 410 variant is closest to malformed SDP?
531000 SdpParsingFailure. Start with the raw SDP body on both directions, then check media lines, transport, crypto details, and attribute consistency.
Can VPN use trigger Teams Phone 410 issues?
It can. Microsoft notes that Teams media should avoid unnecessary middleboxes such as VPN servers and packet shapers because they can affect media quality and routing behavior.
Does IPv6 matter when troubleshooting 410?
Yes. In Teams Phone, IPv6 support is documented for non-media-bypass scenarios, while media bypass with IPv6 and mixed IPv6/IPv4 signaling-media mode are not supported. That design detail can directly shape a 410 investigation.