Health Check - Lenovo RackSwitch G8264 Application Manual

Health Check

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 If the primary VLAG port fails, the secondary VLAG switch forwards traffic to
the receiver. Multicast entries are created on both the VLAG switches: primary
VLAG switch with forward state; secondary VLAG switch with VLAG pruned
state.
 If the secondary VLAG port fails, the primary VLAG switch forwards traffic to
the receiver. Multicast entries are created on both the VLAG switches: primary
VLAG switch with forward state; secondary VLAG switch with pruned state.
If the primary VLAG switch is down, the secondary VLAG switch forwards

traffic to the receiver. When the primary VLAG switch boots up again, it
becomes the secondary VLAG switch and blocks traffic to the receiver. The
VLAG switch that was secondary initially becomes the primary and continues
forwarding traffic to the receiver.
If the secondary VLAG switch is down, the primary VLAG switch forwards

traffic to the receiver. When the secondary VLAG switch is up, it blocks traffic.
The primary switch forwards traffic to the receiver.
 If the uplink to the primary VLAG switch is down, the secondary VLAG switch
forwards traffic to the receiver and to the primary VLAG switch over the ISL.
The primary VLAG switch blocks traffic to the receiver so the receiver does not
get double traffic. Both the VLAG switches will have multicast entries in
forward state.
If the uplink to the secondary VLAG switch is down, the primary VLAG switch

forwards traffic to the receiver and to the secondary VLAG switch over the ISL.
The secondary VLAG switch blocks traffic to the receiver so the receiver does
not get double traffic. Both the VLAG switches will have multicast entries in the
forward state.
When the multicast source is connected to VLAG ports (layer 2 domain), traffic
forwarded by the VLAG routers is managed as follows:
IPMC traffic from the access switch can be hashed to any of the VLAG switches.

Consequently, both the primary and secondary VLAG switches must
synchronize the (S,G) entries for faster failover.
 The Rendezvous Point sends (S,G) entries to either the primary or secondary
VLAG switch, depending on which provides the shortest path to the source.
However, Register‐Stop messages are only sent to the primary VLAG switch.
Based on the shortest path, one of the VLAG switches will forward traffic for a
particular (S,G) entry to the receiver.
For the VLAG multi‐tier topology, an additional L3 backup path to ISL is

supported. On the L3 backup interface, both L3 routing protocols and PIM must
be enabled.
In a VLAG with PIM topology, you must configure health check. See "Health
Check" on page 233.
When health check is configured, and the ISL is down, the primary VLAG switch
forwards traffic to the receiver. The secondary VLAG switch ports will be
errdisable state and will block traffic to the receiver.
Chapter 12: Virtual Link Aggregation Groups
233