Extreme Networks ExtremeWare XOS 11.3, Manual

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Troubleshooting
ExtremeWare XOS 11.3 Concepts Guide
620
VRRP
You cannot define VRRP virtual router parameters:
Before configuring any virtual router parameters for VRRP, you must first create the VRRP instance on
the switch. If you define VRRP parameters before creating the VRRP, you may see an error similar to
the following:
Error: VRRP VR for vlan vrrp1, vrid 1 does not exist.
Please create the VRRP VR before assigning parameters.
Configuration failed on backup MSM, command execution aborted!
If this happens, do the following:
●
Create a VRRP instance using the
create vrrp vlan vrid
command.
●
Configure the VRRP instance’s parameters.
Using Standalone ELRP to Perform Loop Tests
Having a tool to determine if the network has any loops is extremely useful. There are various other
protocols that can exploit this tool to prevent network loops. There are also situations where you might
want to check the topology for the existence or absence of a loop.
The Extreme Loop Recovery Protocol (ELRP) allows you to prevent, detect, and recover from Layer 2
loops in the network. You can use ELRP with other protocols such as ESRP, as described in the section
“Using ELRP with ESRP” on page 476 . Other protocols such as Ethernet Automatic Protection Switching
(EAPS) requires that a network have a ring topology to operate. In this case you can use ELRP to ensure
that the network has a ring topology.
ELRP is used to detect network loops in a Layer 2 network. A switch running ELRP transmits multicast
packets with a special MAC destination address out of some or all of the ports belonging to a VLAN.
All of the other switches in the network treat this packet as a regular, multicast packet and flood it to all
of the ports belonging to the VLAN. If the packets transmitted by a switch are received back by that
switch, this indicates a loop in the Layer 2 network.
Once a loop is detected through ELRP, different recovery actions can be taken such as blocking certain
ports to prevent loop or logging a message to system log. The action taken is largely dependent on the
protocol using ELRP to detect loops in the network.
Using ELRP with ESRP is one way you can use ELRP. For more information about configuring ESRP
and ELRP, see the section
“Using ELRP with ESRP” on page 476 . Another way to use ELRP is to invoke
“standalone” ELRP commands to determine whether a network has an Layer 2 loop or not. The
remaining sections describe how to configure standalone ELRP on your switch.
This section describes the following topics:
●
About Standalone ELRP on page 621
●
Configuring Standalone ELRP on page 621
●
Displaying Standalone ELRP Information on page 622