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Download User`s Manual Version 5.2
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Mediant 1000 When the CPU module loses all Ethernet connectivity, a Critical alarm is generated (displaying 'No Ethernet Link'): 8.3 When MIIRedundancyEnable is disabled: the alarm is generated when the single physical connection is lost. The alarm is cleared when the single physical connection is restored. When MIIRedundancyEnable is enabled: the alarm is generated when both physical connections are lost. The alarm is cleared when one or both of the physical connections are restored. NAT (Network Address Translation) Support Network Address Translation (NAT) is a mechanism that maps a set of internal IP addresses used within a private network to global IP addresses, providing transparent routing to end hosts. The primary advantages of NAT include (1) Reduction in the number of global IP addresses required in a private network (global IP addresses are only used to connect to the Internet); (2) Better network security by hiding its internal architecture. The following figure illustrates the gateway's supported NAT architecture. The design of SIP creates a problem for VoIP traffic to pass through NAT. SIP uses IP addresses and port numbers in its message body and the NAT server can’t modify SIP messages and therefore, can’t change local to global addresses. Two different streams traverse through NAT: signaling and media. A gateway (located behind a NAT) that initiates a signaling path has problems in receiving incoming signaling responses (they are blocked by the NAT server). Furthermore, the initiating gateway must notify the receiving gateway where to send the media. To resolve these issues, the following mechanisms are available: STUN (refer to 'STUN' on page 425) First Incoming Packet Mechanism (refer to 'First Incoming Packet Mechanism' on page 426) RTP No-Op packets according to the avt-rtp-noop draft (refer to 'No-Op Packets' on page 426) For information on SNMP NAT traversal, refer to the SIP Series Reference Manual. SIP User's Manual 424 Document #: LTRT-83302
