H3C Technologies H3C S12500 Series Switches - Manual (Page 15)

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2. Site A's edge device floods the ARP requests out of all interfaces, including the EVI tunnel
interfaces.
3. Site B's edge device de-encapsulates the ARP request and broadcasts the request.
4. IP2 sends an ARP reply back to site A's edge device over the EVI link.
5. Site A's edge device creates an ARP cache entry for the remote MAC address and forwards the
reply to the requesting host.
6. Site A's edge device replies to all subsequent requests for the MAC address of IP2.
Figure 7 ARP flooding suppression
Selective flooding
Selective flooding enables an edge device to send an unknown unicast or multicast frame out of an EVI
tunnel interface.
This feature is designed for special multicast addresses that require flooding across sites and cannot be
added to a multicast forwarding table by IGMP snooping.
For example, you must configure selective flooding for PIM hellos, IGMP general query packets, and
Microsoft NLBS cluster traffic to be sent out of an EVI tunnel interface.
Path MTU
When encapsulating an Ethernet frame in EVI, the edge device does not modify the Ethernet frame, but
sets the DF bit in the IP header. For an Ethernet transport network, the total packet size increases by up
to 46 bytes. Because EVI does not support path MTU discovery, your EVI deployment must make sure the
path MTU of the transport network is higher than the maximum size of EVI tunneled frames.