10
Q.
What is the difference between EVI edge devices and PE devices?
A.
In an EVI network, edge devices are located at the boundaries of customer sites. In an MPLS VPN network,
provider edge (PE) devices are located at the boundaries of the service provider network.
Q.
What are extended VLANs?
A.
Extended VLANs are customer VLANs extended by EVI between remote customer sites over a transport
network. An extended VLAN can be assigned to only one EVI network.
Q.
Under what conditions should I configure selective flood for a MAC address?
A.
By default, EVI does not flood unknown unicast or multicast traffic out of EVI tunnel interfaces to remote sites.
Selective flood enables an edge device to send an unknown unicast or multicast frame out of an EVI tunnel
interface.
You can configure this feature for special multicast addresses that require flooding across sites but cannot be
added to a multicast forwarding table by IGMP snooping.
For example, you must configure selective flood for PIM hellos, IGMP general query packets, and Microsoft
NLBS cluster traffic to be sent out of an EVI tunnel interface.
Q.
How does EVI prevent forwarding loops?
A.
EVI implements split horizon to prevent loops among edge devices. This feature prevents frames received from
EVI tunnels from being forwarded back to the transport network. Split horizon takes effect on all types of frames,
including unicast, multicast, and broadcast.
Q.
How does an edge device handle broadcast, unknown unicast, and unknown multicast traffic?
A.
An EVI edge device floods broadcast, unknown unicast, and unknown multicast traffic as follows:
•
Broadcast frame
—Floods the frame to all interfaces in the VLAN where the frame has been received,
including internal interfaces and EVI-Link interfaces. For ARP packets, you can use the ARP flood suppression
feature to reduce ARP broadcasts.
•
Unknown unicast or multicast frame
—Floods the frame to all internal interfaces in the VLAN where the
frame has been received. The edge device typically does not forward destination-unknown frames to other
sites. If a site-to-site flooding is desirable for a special MAC address, use the selective flood feature.
Miscellaneous
This section contains the most frequently asked questions about other problems.
Q.
When outbound traffic mirroring is configured on a port, why can't some packets sent by the CPU be mirrored
(for example, LACP packets)?
A.
These packets are not sent according to the packet sending logic, so they cannot be mirrored.
