Which two forms of spanning-tree protection are offered by EX Series switches? (Choose two.)
A.
BPDU protection
B.
broadcast protection
C.
core protection
D.
root protection
Explanation:
BPDU Protection for Spanning-Tree Instance Interfaces OverviewBy default, if a Bridge Protocol Data Unit (BPDU) data frame is received on a blocked interface, the system will disable the interface and stop forwarding frames out the interface until the interface is explicitly cleared.
The Spanning-Tree Protocol (STP) family is designed to break possible loops in a Layer2 bridged network. Loop prevention avoids damaging broadcast storms that can potentially render the network useless. STP processes on bridges exchange BPDUs to determine the LAN topology, decide the root bridge, stop forwarding on some ports, and so on. However, a misbehaving user application or device can interfere with the operation of the STP protocols and cause network problems.
On the MX Series routers only, you can configure BPDU protection to ignore BPDUs received on interfaces where none should be expected (for example, a LAN interface on a network edge with no other bridges present). If a BPDU is received on a blocked interface, the interface is disabled and stops forwarding frames. By default, all BPDUs are accepted and processed on all interfaces.
You can configure BPDU protection on interfaces with the following encapsulation types:
Loop Protection for Spanning-Tree Instance Interfaces Overview
Spanning-tree protocol loop protection enhances the normal checks that spanning-tree protocols perform on interfaces. Loop protection performs a specified action when BPDUs are not received on a nondesignated port interface. You can choose to block the interface or issue an alarm when bridge protocol data units (BPDUs) are not received on the port.
The spanning-tree protocol family is responsible for breaking loops in a network of bridges with redundant links. However, hardware failures can create forwarding loops (STP loops) and cause major network outages. Spanning-tree protocols break loops by blocking ports (interfaces). However, errors occur when a blocked port transitions erroneously to a forwarding state.
Ideally, a spanning-tree protocol bridge port remains blocked as long as a superior alternate path to the root bridge exists for a connected LAN segment. This designated port is determined by receiving superior BPDUs from a peer on that port. When other ports no longer receive BPDUs, the spanning-tree protocol considers the topology to be loop free. However, if a blocked or alternate port moves into a forwarding state, this creates a loop.
By default (that is, without spanning-tree protocol loop protection configured), an interface that stops receiving BPDUs will assume the designated port role and possibly result in a spanning-tree protocol loop.
You can configure spanning-tree protocol loop protection to improve the stability of Layer2 networks.
You configure spanning-tree protocol loop protection to prevent selected interfaces from interpreting the lack of received BPDUs as a false positive condition for making the interface the designated port.
* ethernet-bridge
* ethernet-vpls
* extended-vlan-bridge
* vlan-vpls
* extended-vlan-vplsYou can configure BPDU protection on individual interfaces or on all the edge ports of the bridge.