Cisco Expressway Administrator Guide (X15.4) - Firewall Traversal

Publisher

Cisco Systems

URL

https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/expressway/admin_guide/X15-4/exwy_b_cisco-expressway-administrator-guide-x154/exwy_m_firewall-traversal.html

Published

2026-02-09

Updated

unknown

Accessed

2026-09-25

HTTP status

200

License

Cisco website terms of use; all rights reserved; no-redistribution; short excerpts and locators only

Source notes citing this source

• Cisco recommends turning off any H.323 and SIP protocol support (ALG) on the firewall in front of the Expressway. in context
• For H.323 firewall traversal a traversal zone can use either Assent or H.460.18, while SIP traversal uses Assent over a TCP/TLS connection from client to server. in context
• Expressway-E and Expressway-C must not share an address behind NAT, because the firewall cannot distinguish between them. in context
• Expressway supports traversal chaining, in which the first Expressway-E is the traversal server to Expressway-C and a traversal client to a second Expressway-E. in context
• Both the traversal client and the traversal server must be Cisco Expressway systems; neither can be a Cisco VCS. in context
• A traversal client keeps a connection open through the firewall to a designated port on the traversal server using keepalives, and the server sends incoming call requests to the client over that connection. in context
• The default traversal media port range is 36000 to 59999. in context
• Cisco guidance numbers traversal zone ports from TCP 7001 for SIP and UDP 6001 for H.323, incrementing by one for each additional traversal zone. in context

Cite this source record

APA

WarmTransfer. (2026, February 9). Cisco Expressway Administrator Guide (X15.4) - Firewall Traversal. WarmTransfer. https://warmtransfer.net/knowledge/sources/cisco-exwy-admin-x154-firewall-traversal

BibTeX

@misc{warmtransfer-cisco-exwy-admin-x154-firewall-traversal,
  title  = {Cisco Expressway Administrator Guide (X15.4) - Firewall Traversal},
  author = {{WarmTransfer}},
  year   = {2026},
  url    = {https://warmtransfer.net/knowledge/sources/cisco-exwy-admin-x154-firewall-traversal},
  note   = {Cisco Systems, accessed 2026-09-25}
}