Active/Standby determination: Active/Standby determination is controlled by the hosts. They exchange the pertinent information through ORBIT protocol,
which includes electing a priority selection algorithm to use. This algorithm determines the factors that are taken into account
when calculating priority information. The hosts then each send a single numerical priority value to the Satellite. The Satellite
only picks the lowest-host priority value, and forwards data to that host. Independently, the hosts make the same determination,
and the traffic flows bi-directionally between the Active host and the Satellite. The hosts take a number of parameters into
account when calculating the priority value, including the user-configured priority, from the host to the Satellite, and
a tie-break of the chassis MAC for each host.
Cisco IOS XR
Software uses these parameters to calculate the priority, where each item is
more important than any of the subsequent ones. This means that the subsequent
parameters are only taken into account, if the higher-priority items are
identical across the two hosts.
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Connectivity
– Indicates whether the Host and Satellite can currently
exchange data.
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PE isolation – Indicates
that if the PE is isolated, then it defers to the other host.
-
Minimum Links – Indicates that if the number of active links is less than the configured value in bundled ICL, then it defers to the other
host. For more information, see Soft Minimum Active Links for Dual Home Mode.
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Configured Priority – This is as early as possible to allow the greatest flexibility for the operator.
Note
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The host priority switchover functionality does not function when one of the hosts is running an IOS XR release older than
6.1.x and the other host is running 6.1.x or later software releases. In such cases, you must disconnect the host running
the older IOS XR release from the satellites. After a successful disconnection, the satellites switch over to the remaining
hosts. You can also upgrade the disconnected host to the latest software release.
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Parity of the Satellite
ID – This is used as a late tie breaker to provide some load balancing
across two Hosts with numerous hub-and-spoke Satellites, in which the
even-numbered Satellites prefer one host, while the odd-numbered Satellites
prefer the other host.
On a tie-breaker
of all the previous priorities, it falls back to the Primary host, which is the
one with the lowest chassis MAC address based on byte size.
Separate records of interface counters of satellite access ports on either host: - The SDAC protocol that runs between the hosts and satellite reports only the difference in statistics to each host, that
is, the number of packets/bytes since the last update. Clearing the counters on either host clears only the local copy of
the statistics of the satellite access ports. It doesn’t update the interface counters on the satellite itself and the other
host won’t get notified that the counters have been reset on the peer. So, it’s expected that these counters may be different
on each host if you have cleared the counters at different times or if the host-to-satellite connections came up at different
times.
To clear the satellite interface counters on the host, execute the command clear counters on the host router.
To view the interface counters of satellite access ports, execute the command show interface satellite-access-port on the host router.
After clearing counters on Host 1, the statistics for satellite access ports on both hosts are different because only the
local copy of the satellite interface counters on Host 1 got reset.
On Host 1:
Router#clear counters
Clear "show interface" counters on all interfaces [confirm]
Router#show int GigabitEthernet160/0/0/0
GigabitEthernet160/0/0/0 is up, line protocol is up
Interface state transitions: 3
Hardware is GigabitEthernet/IEEE 802.3 interface(s), address is 8478.ac07.6155 (bia 8478.ac07.6155)
Internet address is 10.10.1.1/24
MTU 1514 bytes, BW 1000000 Kbit (Max: 1000000 Kbit)
reliability 255/255, txload 190/255, rxload 127/255
Encapsulation ARPA,
Full-duplex, 1000Mb/s, SX, link type is force-up
output flow control is off, input flow control is off
Carrier delay (up) is 100 msec, Carrier delay (down) is 100 msec
loopback not set,
Last link flapped 23:16:57
ARP type ARPA, ARP timeout 04:00:00
Last input 00:00:00, output 00:00:00
Last clearing of "show interface" counters 00:00:04
5 minute input rate 499313000 bits/sec, 61311 packets/sec
5 minute output rate 748970000 bits/sec, 91966 packets/sec
327104 packets input, 332990972 bytes, 0 total input drops
0 drops for unrecognized upper-level protocol
Received 0 broadcast packets, 1 multicast packets
0 runts, 0 giants, 0 throttles, 0 parity
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
490655 packets output, 499485772 bytes, 0 total output drops
Output 0 broadcast packets, 163552 multicast packets
0 output errors, 0 underruns, 0 applique, 0 resets
0 output buffer failures, 0 output buffers swapped out
0 carrier transitions
Satellite access port counters on Host 2 are not reset and so different from the values on Host 1:
On Host 2:
Router#show int GigabitEthernet160/0/0/0
GigabitEthernet160/0/0/0 is up, line protocol is up
Interface state transitions: 3
Hardware is GigabitEthernet/IEEE 802.3 interface(s), address is 8478.ac07.6155 (bia 8478.ac07.6155)
Internet address is 10.10.1.1/24
MTU 1514 bytes, BW 1000000 Kbit (Max: 1000000 Kbit)
reliability 255/255, txload 191/255, rxload 127/255
Encapsulation ARPA,
Full-duplex, 1000Mb/s, SX, link type is force-up
output flow control is off, input flow control is off
Carrier delay (up) is 100 msec, Carrier delay (down) is 100 msec
loopback not set,
Last link flapped 23:17:03
ARP type ARPA, ARP timeout 04:00:00
Last input 00:00:00, output 00:00:00
Last clearing of "show interface" counters 02:32:13
5 minute input rate 499495000 bits/sec, 61333 packets/sec
5 minute output rate 749243000 bits/sec, 92000 packets/sec
541290577 packets input, 551031306258 bytes, 0 total input drops
0 drops for unrecognized upper-level protocol
Received 0 broadcast packets, 2628 multicast packets
0 runts, 0 giants, 0 throttles, 0 parity
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
807585148 packets output, 822119157464 bytes, 0 total output drops
Output 0 broadcast packets, 269196783 multicast packets
0 output errors, 0 underruns, 0 applique, 0 resets
0 output buffer failures, 0 output buffers swapped out
0 carrier transitions