Unknown Unicast Flooding Supperssion

This chapter describes how to configure unknown unicast flooding supperssion on the Cisco ASR 1000 Series Routers. This chapter contains these topics:

About Unknown Unicast Flooding on Bridge Domain

Occasionally, unknown unicast traffic is flooded to all the provider edge device because the device does not know the destination MAC address of a received packet. By default the unknown unicast traffic will be flooded to all the devices. To prevent forwarding such traffic, you can configure unknown-unicast-suppress Suppress unknown unicast flooding command.

Limitations for Unknown Unicast Suppression

If the Unknown Unicast Flooding Suppression is on, the unicast traffic towards an unknown host will be dropped. A host becomes unknown or silent when its MAC address ages out from the MAC address table on the PE. The PE might rely on the Unknown Unicast Flooding to re-learn the MAC address.

Enabling Unknown Unicast Flooding on Bridge Domain

To enable unknown unicast flooding suppression, perform the following steps.


Note

By default, the unknown unicast flooding is disabled.

SUMMARY STEPS

  1. configure terminal
  2. bridge-domain {interface number}
  3. flooding-suppression unknown-unicast
  4. end

DETAILED STEPS

  Command or Action Purpose

Step 1

configure terminal

Example:


Router# configure terminal

Enters global configuration mode.

Step 2

bridge-domain {interface number}

Example:


Router(config)# bridge-domain 10

10

Configures the bridge domain on the interface.

Step 3

flooding-suppression unknown-unicast

Example:


Router(config-bdomain)# flooding-suppression unknown-unicast

Enables unknown unicast flooding suppression on the bridge domain.

Step 4

end

Example:


Router(config-bdomain)# end

(Optional) Returns to privileged EXEC mode.

Verifying the Unknown Unicast Flooding Suppression

Verify that you have enabled the unknown unicst flooding suppression by entering the following command:
Device(config-bdomain)#do show run | sec bridge
bridge-domain 10
flooding-suppression unknown-unicast

This examples shows the packets that are suppressed and dropped.

Device# show pla hard qfp ac fe bridge-domain datapath 1 
QFP L2BD Bridge Domain information


BD id                  : 1
State enabled          : Yes
Aging timeout (sec)    : 300
Aging active entry     : Yes
Max mac limit          : 65536
Unkwn mac limit flood  : Yes
mac_learn_enabled      : Yes
mac_learn_controled    : Yes
Unknown unicast olist  : Yes
otv_aed_enabled : No
otv_enabled : No
mcast_snooping_enabled : No
Feature : evpn, uuf-suppression
SISF snoop protocols   : arp, ndp, dhcpv4, dhcpv6 
Mac learned            : 0
BDI outer vtag         : 00000000
BDI inner vtag         : 00000000

Replication tree info:
  Global replication    : depth encode 0X2000001, (head 0X29D3D000)
  Split-horizon-group 0 : depth encode 00000000, (head 00000000)
  Split-horizon-group 1 : depth encode 00000000, (head 00000000)

Bridge Domain statistics

Total bridged                pkts : 0          bytes: 0
Total unknown unicast        pkts : 0          bytes: 0
Total broadcasted            pkts : 0          bytes: 0
Total to BDI                 pkts : 0          bytes: 0
Total injected               pkts : 0          bytes: 0
Total mac-sec violation drop pkts : 0          bytes: 0
Total mac-sec move drop      pkts : 0          bytes: 0
Total mac-sec unknown drop   pkts : 0          bytes: 0
Total source filter drop     pkts : 0          bytes: 0
Total bfib policy drop       pkts : 0          bytes: 0
Total replication start drop pkts : 0          bytes: 0
Total recycle tail drop      pkts : 0          bytes: 0
Total static MAC move drop   pkts : 0          bytes: 0
Total BD disabled drop       pkts : 0          bytes: 0
Total STP state drop         pkts : 0          bytes: 0
Total UUF suppression drop   pkts : 0          bytes: 0

Feature Information for Unknown Unicast Flooding Suppression

Table 1. Feature Information for Unknown Unicast Flooding Suppression

Feature Name

Releases

Feature Information

Unknown Unicast Flooding Suppression

Cisco IOS XE Bengaluru 17.4

This feature was introduced.