A Unified CM cluster upgraded from 8.x or earlier may keep a 5000-byte SIP Max Incoming Message Size; raising it to 11000 fixes B2B calls rejected as 'large message'.
Checked 2026-09-25
- Vendor
- Cisco
- Product
- Cisco Unified CM
- Subsystem
- service parameters
- Deployment
- on-premises
- Region
- not restricted
- Release range
- clusters upgraded from Unified CM 8.x or earlier
- Checked
- 2026-09-25
Sources
- Troubleshoot Most Common Issues for Business to Business Calls Through Expressway — Cisco Systems · tier 2 current vendor documentation · Issue: large SIP messages rejected
Cite this note
APA
WarmTransfer. (2026, September 25). Setting up business-to-business calling on Cisco Expressway: source note expressway-b2b-setup-cucm-max-message-size. WarmTransfer. https://warmtransfer.net/knowledge/claims/expressway-b2b-setup-cucm-max-message-size
BibTeX
@misc{warmtransfer-claim-expressway-b2b-setup-cucm-max-message-size,
title = {Setting up business-to-business calling on Cisco Expressway: source note expressway-b2b-setup-cucm-max-message-size},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/expressway-b2b-setup-cucm-max-message-size},
note = {Source note expressway-b2b-setup-cucm-max-message-size, checked 2026-09-25}
}