Temporary Fix for Delay in Call Completion on SIP Cisco Unified Border Element Gateway
Question
A collaboration engineer is troubleshooting a delay in call completion on a SIP Cisco Unified Border Element gateway.
The gateway is set up for dual stack IP with DNS as the dial peer target.
In DNA, AAAA and A records are configured for the target.
The engineer determines that IPv4 calls should remain IPv4, when possible, to temporary resolve the issue.
The company is testing some IPv6 applications so the engineer cannot disable IPv6 altogether.
Which configuration can the engineer apply to the Cisco Unified Border Element to accomplish this temporary fix?
Answers
Explanations
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A. B. C. D. E.D.
The issue at hand is a delay in call completion on a SIP Cisco Unified Border Element gateway, which is set up for dual stack IP with DNS as the dial peer target. There are AAAA and A records configured for the target in DNA, which means that both IPv4 and IPv6 addresses are available for the target.
The engineer determines that IPv4 calls should remain IPv4, when possible, to temporarily resolve the issue. However, the company is testing some IPv6 applications, so the engineer cannot disable IPv6 altogether.
To accomplish this temporary fix, the engineer needs to configure the Cisco Unified Border Element to prefer IPv4 calls over IPv6 calls. There are several configuration options provided in the answers, but only one will achieve this goal.
Answer A: sip-ua protocol mode ipv4 is incorrect because it only configures the SIP user agent to use IPv4, but it doesn't influence the way calls are processed.
Answer B: voice service voip sip no anat is incorrect because it disables Application-level gateway (ALG) processing, which is not related to the issue at hand.
Answer C: voice service voip no allow-connections ipv4 to ipv6 is incorrect because it disables connections between IPv4 and IPv6 addresses, which is not what the engineer wants to achieve.
Answer D: sip-ua protocol mode dual-stack preference ipv4 is the correct answer because it configures the SIP user agent to prefer IPv4 over IPv6 when initiating calls.
Answer E: voice service voip sip preference ipv4 is incorrect because it only configures the SIP preference to use IPv4, but it doesn't influence the way calls are processed.
In summary, the correct configuration to temporarily resolve the delay in call completion on a SIP Cisco Unified Border Element gateway that is set up for dual stack IP with DNS as the dial peer target is to configure the sip-ua protocol mode dual-stack preference ipv4.
