EVPN defines a mechanism to protect the EVPN service from control plane churn as a result of loops or accidental duplicated MAC addresses. The 7210 SAS supports an enhanced version of this procedure, which is described in this section.
In a scenario where two or more hosts are misconfigured using the same (duplicate) MAC address, the duplicate MAC address is learned by the PEs in the VPLS. As a result, the traffic originating from the hosts triggers continuous MAC moves among the PEs attached to the hosts. It is important to recognize such situations and avoid incrementing the sequence number (in the MAC Mobility attribute) to infinity.
To remedy accidentally duplicated MAC addresses, a router that detects a MAC mobility event through local learning starts a window in-minutes timer (the default value is 3). If the configured num-moves num value is detected before the timer expires (the default value is 5), the router concludes that a duplicate MAC situation has occurred and sends a trap message to alert the operator. Use the show service id svc-id bgp-evpn command to display the MAC addresses. The following is a sample configuration output.
10 2014/01/14 01:00:22.91 UTC MINOR: SVCMGR #2331 Base
"VPLS Service 1 has MAC(s) detected as duplicates by EVPN mac-
duplication detection."
# show service id 1 bgp-evpn
===============================================================================
BGP EVPN Table
===============================================================================
MAC Advertisement : Enabled Unknown MAC Route : Disabled
MPLS Admin Status : Enabled Creation Origin : manual
MAC Dup Detn Moves : 5 MAC Dup Detn Window: 3
MAC Dup Detn Retry : 9 Number of Dup MACs : 1
-------------------------------------------------------------------------------
Detected Duplicate MAC Addresses Time Detected
-------------------------------------------------------------------------------
00:00:00:00:00:12 01/14/2014 01:00:23
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===============================================================================
After a duplicate MAC address is detected, the router stops sending and processing BGP MAC advertisement routes for that MAC address until one of the following occurs:
The MAC is flushed because of a local event (SAP or SDP-binding associated with the MAC fails) or the reception of a remote update with better SEQ number (because of a MAC flush at the remote router).
The retry in-minutes timer expires, which flushes the MAC and restarts the process.
The other routers in the VPLS instance forward the traffic for the duplicate MAC address to the router advertising the best route for the MAC.
The values of num-moves and window can be configured for different environments. In scenarios where BGP rapid-update EVPN is configured, the operator should configure a shorter window timer than scenarios where BGP updates are sent per the configured min-route-advertisement interval, which is the default.
The preceding MAC duplication parameters can be configured per VPLS service under the bgp-evpn mac-duplication context. The following is a sample configuration output.
A:Dut-B>config>service>vpls>bgp-evpn# info
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evi 1
mac-duplication
detect num-moves 5 window 2
retry 10
exit
mpls
split-horizon-group "vpls1"
ingress-replication-bum-label
auto-bind-tunnel
resolution-filter
ldp
exit
resolution filter
exit
no shutdown
exit
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