iosxr-on-box-automation
IOS XR Automation Scripts
The scripts available on-box can now leverage Python libraries, access the underlying router information to execute CLI commands, and monitor router configurations continuously. This results in setting up a seamless automation workflow by improving connectivity, access to resources, and speed of script execution. The following categories of on-box scripts are used to achieve operational simplicity:
- Configuration (Config) scripts
- Execution (Exec) scripts
- Process scripts
- Embedded Event Manager (EEM) scripts
Deploying and using EEM scripts on the router is described here.
PIM DR priority EEM script
IOS XR does not support HSRP Aware PIM, a redundancy mechanism for the Protocol Independent Multicast (PIM) protocol to interoperate with Hot Standby Router Protocol (HSRP). It allows PIM to track HSRP state and to preserve multicast traffic upon failover in a redundant network with HSRP enabled.
This workaround uses object tracking to detect PE core isolation and uses EEM policy-maps to change the configured PIM DR priorities dynamically. The new priority value is set to the value after the word priority in the policy-map name. The tracked object should have an up delay configured, to give protocols time to converge once the PE is not isolated from the core anymore.
Example usage
Required configuration:
- User and AAA configuration
The multi event trigger is optional as the Startup event is redundant. The below configuration will result in setting the priorities to 95 two times when the router boots, as the Startup event will occur before the very first Isolate event. The interfaces are down when the router boots, so just triggering on Isolate should be sufficient.
event manager action Pim
username <user>
type script script-name pim.py checksum sha256 <checksum>
!
event manager policy-map Set-Priority-95
trigger multi-event "Startup OR Isolate"
action Pim
!
event manager policy-map Set-Priority-110
trigger event Restore
action Pim
!
event manager event-trigger Isolate
type track name 1 status down
!
event manager event-trigger Restore
type track name 1 status up
!
event manager event-trigger Startup
type timer cron cron-entry "@reboot"
!
track 1
type line-protocol state
interface GigabitEthernet0/0/0/0
!
delay up 60
!
BGP graceful maintenance EEM script
CE-PE traffic can be blackholed when a PE is isolated from the core while local prefixes are still advertised. BGP Graceful Maintenance is used as a workaround for this. When activated, the affected routes are advertised again with a reduced preference. This causes neighboring routers to choose alternative routes. You can use any of the following methods to a signal reduced route preference:
- Add GSHUT community
- Reduce LOCAL_PREF value
- Prepend AS Path
Object tracking is used to detect core isolation and EEM policy-maps are used to dynamically (de)activate BGP Graceful Maintenance. The word activate or deactivate in the policy-map name determines the new state. The tracked object should have an up delay configured, to give protocols time to converge once the router is not isolated anymore.
Example usage
The event-triggers and tracked object from the above example are used here as well.
event manager action BGP
username <user>
type script script-name bgp.py checksum sha256 <checksum>
!
event manager policy-map Activate
trigger multi-event "Startup OR Isolate"
action BGP
!
event manager policy-map Deactivate
trigger event Restore
action BGP
!
Commit syslog EEM script
This EEM script implements the IOS style archive log config syslog notification for IOS XR. The syslog event trigger is used to detect a commit. A syslog message is generated for each committed configuration line.
Example usage
event manager action Log-Config
username <user>
type script script-name commit.py checksum sha256 <checksum>
!
event manager policy-map Archive
trigger event Commit
action Log-Config
!
event manager event-trigger Commit
type syslog pattern "%MGBL-CONFIG-6-DB_COMMIT : Configuration committed by user"
!
LPTS drop monitor process script
A process script differs from an EEM script because a process script runs forever and cannot interact with the CLI as it does not have a user associated with it. Deploying and using process scripts on the router is described here.
This script provides alerting functionality to LPTS. The commands used for measuring drop counts are show lpts pifib hardware police location <line card> and show lpts pifib hardware static-police location <line card>. If the LPTS drops exceed a certain threshold within a preset interval, a syslog message is generated. Different thresholds can be set for different flow types. The wildcard flow type, indicated by a star, is required. A threshold value must be specified for each flow type.
Example usage
The next example sets an interval of 60 seconds and a threshold of 1000 packets to the BGP-known flow type and a threshold of 10 packets for all others.
appmgr
process-script Lpts-Mon
executable lpts.py
run-args -i 60 -f * BGP-known -t 10 1000
!
!
script process lpts.py checksum SHA256 <checksum>
Example output
RP/0/RSP0/CPU0:Feb 25 13:59:37.362 CET: scripting_python3[67253]: %OS-SCRIPT_LOG-6-INFO : Script-LPTS: LPTS drop threshold (10) exceeded for flow type PIM-mcast-known on 0/1/CPU0, 120318 drops in last 60 seconds.
RP/0/RSP0/CPU0:Feb 25 13:59:37.945 CET: scripting_python3[67253]: %OS-SCRIPT_LOG-6-INFO : Script-LPTS: LPTS drop threshold (10) exceeded for flow type PUNT_MAC_SECURE_VIOLATION on 0/1/CPU0, 2204316 drops in last 60 seconds.
Storm control drop monitor process script
This script will monitor the drop count over a predefined time interval. If the drops exceed a certain threshold value then a syslog message will be generated. The command used for measuring drop counts is 'show l2vpn bridge-domain detail'. The threshold argument takes either a single value for BUM traffic or a list of three values to specify broadcast, multicast and unknown unicast respectively. If you don't specify a value for the thresholds the default will be 100p.
Example usage
The next example sets an interval of 60 seconds and all thresholds to 10 packets.
appmgr
process-script Storm-Ctrl-Mon
executable storm.py
run-args -i 60 -t 10
!
!
script process storm.py checksum SHA256 <checksum>
Example output
RP/0/RSP0/CPU0:Feb 25 14:00:28.782 CET: scripting_python3[66324]: %OS-SCRIPT_LOG-6-INFO : Script-Storm: Multicast traffic drop exceeded threshold 10p/60s on BG:EVC_00010_BD Bundle-Ether10100.10 Exact value: 60
RP/0/RSP0/CPU0:Feb 25 14:00:28.805 CET: scripting_python3[66324]: %OS-SCRIPT_LOG-6-INFO : Script-Storm: Multicast traffic drop exceeded threshold 10p/60s on BG:EVC_00010_BD neighbor: 10.254.255.2, ID: 36885:10 Exact value: 19
RP/0/RSP0/CPU0:Feb 25 14:01:28.795 CET: scripting_python3[66324]: %OS-SCRIPT_LOG-6-INFO : Script-Storm: Multicast traffic drop exceeded threshold 10p/60s on BG:EVC_00010_BD Bundle-Ether10100.10 Exact value: 11
RP/0/RSP0/CPU0:Feb 25 14:01:28.818 CET: scripting_python3[66324]: %OS-SCRIPT_LOG-6-INFO : Script-Storm: Multicast traffic drop is below threshold 10p/60s on BG:EVC_00010_BD neighbor: 10.254.255.2, ID: 36885:10
RP/0/RSP0/CPU0:Feb 25 14:02:28.817 CET: scripting_python3[66324]: %OS-SCRIPT_LOG-6-INFO : Script-Storm: Multicast traffic drop is below threshold 10p/60s on BG:EVC_00010_BD Bundle-Ether10100.10
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