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If you have a strong Cisco background, then you immediately think of Spanning Tree Protocol when you think of Layer 2 loop protection. Or if you’re keeping abreast of the newest developments, you think of TRILL and SPB. But there are other mechanisms for helping detect loops at layer 2. Here’s one I came across while studying for HP Master ASE: HP Procurve Loop-Protection.
According to the documentation:
Loop protection provides protection against loops by transmitting loop protocol packets out of ports on which loop protection has been enabled. When the switch sends out a loop protocol packet and then receives the same packet on a port that has a receiver-action of send-disable configured, it shuts down the port from which the packet was sent.
![Spanning Spanning](/uploads/1/1/8/5/118598545/993760815.jpg)
After configuring loop guard. This example shows that, by executing spanning-tree 20 loop-guard, loop guard has been configured on port 20 of Switch 2. HP Switch(config)#: show spanning-tree Spanning Tree Information STP Enabled No: Yes Mode: RPVST Extended System ID: Enabled Ignore PVID Inconsistency: Disabled RPVST Enabled VLANs: 20 Switch MAC Address: 002347-c651c0 Root Guard Ports. Hewlett Packard Enterprise Support Center HPE Support Center. Hello all, Can someone explain to me the equivalent configuration of the following commands on Cisco switches for the HP ProCurve switches? Interface range f0/1 spanning-tree portfast end copy run start.
So it’s not doing anything fancy - just using its own protocol packet to detect loops back to the switch itself. Note this is different to Cisco’s loopback detection, which will detect a switchport looped back on itself - e.g. due to faulty wiring - but will not detect a cable run from one port to another on the same switch. Configuration is quick and easy, and it seems to work well. It should work well in any situation where you have edge ports that users might connect together, possibly via a ‘dumb’ switch that doesn’t forward STP BPDUs. These loop protection frames should be forwarded.
Hp Procurve Spanning Tree Priority
Let’s take a quick look at the configuration and operation on my lab switch, an HP 2910al-24G Procurve switch, running W.15.08.0012. The default configuration is for loop-protection to be disabled:
In my lab, I’ve run a cable between ports 21 and 22, so we can simulate a loop. Currently both ports are shut down. Spanning-tree is disabled on this switch, so if I enable those ports, we’ve got a loop, and things will get messy. Let’s configure loop protection, and then enable the ports:
OK, let’s take a look at what’s happened with our ports:
Pretty simple hey? One of the ports has been shut down, as expected. It has been logged, and an SNMP trap (
OID: 1.3.6.1.4.1.11.2.14.11.5.1.12.1.5.6.1
) has been generated. We’ve got the “Port Disable Timer” at the default of “Disabled” - this means that the port will stay shut down until we take manual action. We’d like it to re-enable after 10s, so we configure this:Now if we keep an eye on the output of
show loop-protect
we can see the Loop Count incrementing, as the port gets re-enabled, detects a loop, and shuts down again:![Portfast Portfast](https://community.hpe.com/hpeb/attachments/hpeb/switching-e-series-forum/9900/1/Diagram switch HP.png)
So now you can set a disable timer, and once users remove the loop, their network ports will come back up, without needing any input from the local network admin. All up, this is an easy feature to configure, and should be used on all edge ports on Procurve switches.
Comware has a very similar feature, called loopback-detection. Currently I don’t have any Comware-based devices in my lab though…unless someone wants to donate some?
Related Supplies, Accessories, & Products
Hp Procurve 2910al 48g
more Product Information in pdf format
Hp Procurve Switch Firmware
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The HP Procurve managed 24-port switch has 10/100BASE-TX autosensing per port and 2 open transceiver slots for media flexibility. The HP Procurve switch 2524 is ideal for low-cost, managed 10/100 connectivity with uplinks. | |||||||||||||||||||||||||||
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