Selective Flooding; Path Mtu - H3C S7500X Series Configuration Manual

Hide thumbs Also See for S7500X Series:

Table of Contents

ARP flood suppression uses the following workflow:

Host IP1 in site A sends an ARP request to obtain the MAC address of IP2.

Site A's edge device floods the ARP requests out of all interfaces, including the EVI tunnel

interfaces.

Site B's edge device de-encapsulates the ARP request and broadcasts the request.

IP2 sends an ARP reply back to site A's edge device over the EVI link.

Site A's edge device creates an ARP cache entry for the remote MAC address and forwards the

reply to the requesting host.

Site A's edge device replies to all subsequent requests for the MAC address of IP2.

Figure 6 ARP flood 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 but 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.

When encapsulating an Ethernet frame in EVI, the edge device does not modify the Ethernet frame,

but it sets the DF bit in the IP header. For an Ethernet transport network, the total size of an EVI

protocol packet increases by 46 bytes, and the total size of a data packet increases by 38 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.

Table of Contents