What is lre port

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Print page Print document pages. Rename the bookmark. Delete bookmark? Cancel Delete. Delete from my manuals? Sign In OR. Don't have an account? Sign up! Restore password. Upload manual. Upload from disk. Upload from URL. Cables have higher attenuation at higher frequencies and also interfere with other pairs in the bundle at higher frequencies. This interference or cross talk can significantly impact the signal quality.

When assigning a profile to a switch LRE port, keep these considerations in mind:. On the LRE link, the downstream transmission runs in a low-frequency band from approximately 1 to 3. The upstream transmission runs in a high-frequency band from approximately 4 to 8 MHz.

Higher frequencies are more susceptible to interference. Consequently, upstream signals are susceptible to cross-talk and disruption on the link. To maintain the quality of the LRE connection, use the asymmetric port profiles. These profiles use a low upstream rate but provide a high downstream rate. Microfilters improve voice call quality when voice and data equipment are using the same telephone line. They also prevent nonfiltered telephone rings and nonfiltered telephone transitions such as on-hook to off-hook from interrupting the LRE connection.

For details on which profile to use elsewhere, consult the regulations for connecting to the PSTN in your area. However, LRE signaling is not compatible with T1 signals in the same cable bundle. Follow these guidelines when configuring CPE Ethernet links:. You can configure the CPE Ethernet port to operate at 10 or Mbps and at half- or full-duplex mode, depending on the capability of the remote Ethernet device.

Autonegotiation for port speed and duplex mode is supported. The default speed for the CPE Ethernet port is auto. The default duplex mode is half duplex with back pressure. When the default speed is set to 10 or Mbps with half duplex, the values set are the same. Table shows the speed and duplex settings on the CPE Ethernet port and the switch Ethernet port.

Note The LRE link speed and duplex values are profile independent. Use duplex autonegotiation only if the remote device supports The PC user should notice no significant difference in performance between Mbps half duplex and Mbps full duplex. Autonegotiation for CPE port speed and duplex mode is supported. The default speed for the CPE Ethernet ports is auto.

The default duplex mode is half duplex at Mbps with back pressure. You can enable or disable the CPE Ethernet ports on a per-port basis. The loopback interface configuration command is not supported on the LRE ports. External loopback on the LRE ports is also not supported. Global profiles are set on a switch-wide basis.

Port sequences, global sequences, and port profiles have priority over global profiles see the "Precedence" section. If you assign a global profile to the switch, it cannot override any previously or subsequently set sequence port profile. Changes to the global profile settings are immediately put in effect, and the global mode automatically becomes the active mode.

Enter the global profile name. Select from the list in Table or Table For information about these commands, refer to the switch command reference.

You can set profiles on a per-port basis. You can assign the same profile or different profiles to the LRE ports on the switch. The switch resets the ports with the updated profile settings when they are changed.

Enter interface configuration mode, and specify the LRE port to be configured. Enter the port profile name select from the list in Table or Table Global sequences are set on a switch-wide basis.

If you assign a global sequence to the switch, it overrides any previously or subsequently set profiles. Changes to the global sequence settings are immediately put in effect, and the global mode automatically becomes the active mode. Enter the global sequence name. Select from the list in Table and Table You can set sequences on a per-port basis. You can assign the same sequence or different sequences to the LRE ports on the switch. If you assign a sequence on a per-port basis, it overrides any previously or subsequently set profiles or global sequence.

The switch resets the ports with the updated sequence settings when they are changed. Enter interface configuration mode, and enter the number of the LRE port to be configured.

Enter the port sequence name select from the list in Table or Table For more information about these commands, refer to the switch command reference. You can use the rate selection feature to automatically choose a profile from a set of profiles that the switch port uses to establish an LRE link a link between an LRE switch port and an attached CPE device.

Rate selection is enabled by default, but you must choose a sequence for rate selection to start in other words, there is no default sequence defined. When rate selection is running, the switch chooses the profile for the LRE interface from a sequence, or predefined series of profiles, that are configured for that interface.

The rate-selection algorithm begins with the first profile in the sequence and successively tries the next profiles in descending order until a link is established with the CPE device. When rate selection is enabled, the LRE switch executes rate selection in these scenarios:.

In any of these cases, rate selection obtains the optimal profile for your line conditions. Note When an LRE link is lost for fewer than 25 seconds, the switch does not execute rate selection to re-establish the link.

The link is re-established at the profile used before link loss. The switch chooses the appropriate profile for an LRE interface when it executes rate selection.

If line conditions of the LRE interface change, rate selection must be executed again. The rate selection feature can be applied at both the port level and at the switch level. Profiles and sequences have a system-defined priority level that work with rate selection to determine the rate for a port or the entire switch. Port sequences have the highest priority; that is, they take precedence over any other profile or sequence. The priority levels, from highest to lowest, are as shown:.

Port sequence : rate selection is enabled on the given port only with the given sequence. Global sequence : rate selection is enabled for the entire switch with the given sequence. Port profile : rate selection is enable for the given port only with the given profile. Global profile : rate selection is enabled for the entire switch with the given profile. See Table and Table for the list of profiles and Table and Table for the list of system-defined sequences.

Note If rate selection is disabled for a port, then profiles are used. You can also use rate selection as an installation tool to lock in a particular profile.

In this case, you execute rate selection only once at installation; afterwards, rate selection is never executed, even if one of the four listed events occur. You use the config privileged EXEC command to lock the profile chosen by rate selection. You can enter a special EXEC command to rerun rate selection on the interfaces that have locked the profiles, as needed.

An advantage to profile locking is that the convergence time during bootup is faster if a profile is locked on an LRE port rather than having to go through a profile sequence. When rate selection is running, the SNR is used as an indicator of link quality. The switch does not provide any internal mechanism to ensure link quality. There can be different requirements for link quality, depending on the required bit-error rate and the noise level of the environment.

A noisier environment would require a higher SNR to be able to provide a stable link. A lower bit-error rate would require a higher SNR. Typically a 6-dB margin provides an error rate of 10 bits. To provide link stability, you should add a margin to the required SNR. You can configure your margins to an amount that is appropriate for the noise level of your environment. Increasing the margin requirement can cause the system to choose a lower profile, which would in turn translate to a lower rate but with a higher reach.

The switch does not guarantee any margins after a link is activated; margins are only guaranteed only when the link is established. When a link is activated, if the SNR requirements do not match the configured margin level, the link is not established.

Downstream means the remote end of the link, and upstream the local end. The link has to satisfy both the local and remote margin requirements. If either one is not met, the link is advertised as down. This command has no significance if rate selection is disabled on the interface. Table and Table list the SNR requirements for downstream rates for different profiles.

Table and Table list the SNR requirements for upstream rates for different profiles. The margin range for link qualification is from 1 to 10 dB. The recommended value in a low-noise environment is 2 dB.

The recommended value for medium noise environment is 4 dB. The recommended value in a high noise environment is 6 dB. User-Space Routing Software. The Quagga Project. The routed Daemon.

GateD 3. The Bird Project. Multicast Routing Daemons: mrouted and pimd. Chapter 3. Kernel Requirements for a Full-Featured Lab. The sysctl Facility. Ethernet Channel Bonding. Multicast Support. Firewall and Traffic-Shaping Support. The IPv6 Protocol Stack. Chapter 4. Wireless Technologies. Powerline Communications. ATM Interfaces. Cable Access Ethernet Interfaces. DSL Access. Lab Synchronous Serial Connection Setup. Chapter 5. Ethernet and VLANs. Ethernet NICs. Hubs, Bridges, and Multilayer Switches.

Alias Interfaces. VLAN Configurations. A Few Words on Cabling. Lab Linux Bridging and the Spanning Tree. A Few Words on Layer 2 Security. Exercise STP Operation. Chapter 6. Terminal Emulation Software. Secure Shell Tools. Protocol Analyzer. Statistical Tools. Port Scanners.