Reference Guide

478 | Layer 2
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Per-VLAN MAC Learning Limit
Per-VLAN MAC Learning Limit is available only on platform: e
An individual MAC learning limit can be configured for each VLAN using Per-VLAN MAC Learning
Limit.
One application of Per-VLAN MAC Learning Limit is on access ports. In Figure 22-1, an Internet
Exchange Point (IXP) connects multiple Internet Service Provider (ISP). An IXP can provide several types
of services to its customers including public an private peering. Public peering means that all customers are
connected to one VLAN, and if one ISP wants to peer with another ISP, it establishes a BGP peering
session over this VLAN. Private Peering means that the IXP sets up a separate VLAN between two
customers that want to peer privately; only the ports of these two ISPs would belong to this VLAN, and
they would peer via BGP. In Figure 22-1, Per-VLAN MAC Learning Limit is used on the access ports for
the ISPs that have subscribed to private and public peering since these access ports are members of
multiple VLANs.
Figure 22-1. Per-VLAN MAC Learning Limit
Task Command Syntax Command Mode
Configure a MAC learning limit on a
VLAN.
mac learning-limit limit vlan vlan-id INTERFACE
Display the MAC learning limit
counters for a VLAN.
show mac learning-limit [interface slot/port [vlan
vlan-id]]
EXEC Privilege
interface GigabitEthernet 1/1
...
mac learning-limit 1 vlan 10
mac learning-limit 1 vlan 20
ISP A
ISP B
ISP C
ISP A, B, and C are all public peers through VLAN 10.
In addition, ISP A and C are private peers on a separate
VLAN, VLAN 20. Since the access ports for ISP A
and C are members of multiple VLANs, Per-VLAN MAC
Learning Limit can be applied to those ports.
Internet Exchange Point
802.1QTagged