Brocade Multi-Service IronWare Switching Configuration Guide (Supporting R05.6.00) - Manual (Page 753)

Multi-Service IronWare Switching Configuration Guide 723
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Tunnel statistics for a GRE tunnel or IPv6 manual tunnel
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Statistics polling on the MP and LP
The LP module polls the statistics once every second. For every one second, the module polls the
statistics either for 5000 entries or until the completion of a specific application. (The same polling
mechanism is also used for other applications, such as IP, MPLS, L3VPN, VLL, VPLS and IP Tunnel.)
After all the applications are polled, the system waits for 220 seconds to schedule the next polling
event. However, the LP module synchronizes statistics to the MP every 30 seconds, so 30 seconds
is the granularity of statistics.
The LP synchronizes statistics to the MP in background every 30 seconds, and the MP stores the
statistics for all tunnels for every LP module. If a LP module at either the tunnel ingress or egress,
the system uses the current stored statistics for that LP module for display (and continue to poll the
rest of working modules to get the latest statistics). This mechanism ensures that the tunnel
counters never go down (if no clear statistics command is performed on the tunnel).
When a tunnel is down, the LP does not poll the statistics for that tunnel. The LP keeps the old
counters as is until you explicitly clear them on the CLI. These counters are displayed when the
tunnel is down. When the tunnel comes back up, it resumes polling and adds the new packet
counts to the stored statistics and displays the updated statistics.
Clearing the statistics
When you issue the clear statistics tunnel [tunnel-id] command, the operation clears statistics for
either one or all of the tunnels regardless of the circumstance— whether the tunnel is up or down,
on an ingress or egress module, and so on. Refer to
“Clearing GRE tunnel and manual IPv6 tunnel
statistics” on page 724 for a description of the clear statistics tunnel command.
Tunneled packets that encounter an ACL
If a packet reaches the ACL permit or deny clauses for the inner IPv4 or IPv6 addresses when it
comes through the IP tunnel at the egress node, the packet is not counted as a receive-from-tunnel
packet. Instead, it is counted as an ACL packet. You can view ACL packets by using the show
access-list accounting command.
IPv6 ACL lookup is performed on the inner IPv6 packet at the tunnel egress. This depends on the
port register for the Layer 2 ACL or Layer 3 ACL control, which is performed in parallel.
Switchover behavior
The LP sends statistics to both the active and the standby MP modules. If an MP switches over, the
new-active MP polls the statistics again so it can display the latest statistics. The counters are
equal to or greater than the statistics before the switchover for the working modules. If any module
goes down before the switchover, the new active MP uses the stored counters to display the
statistics for that module.
Hitless operating system upgrade behavior
When a hitless operating system (OS) upgrade occurs, the tunnel statistics are saved and retrieved
after the reset of the LP is complete. The system can retrieve the old statistics and do the polling to
get the latest PRAM statistics. After the hitless upgrade, the system can display the correct packet
counters.