IS-IS Microloop-Avoidance Commands
This chapter describes the IS-IS microloop-avoidance commands:
microloop-avoidance
Use this command to enable microloop avoidance using ordered FIB (oFIB) for an ISIS process.
Use the no form of this command to disable microloop avoidance for an ISIS process.
Microloop avoidance will be enabled with default hold-timer and max-fib values if it is not configured by the user:
• Default value of hold-timer is 6 seconds
• Default value for max-fib is 2 seconds
Microloop avoidance has to be enabled in conjunction with a fast reroute (FRR) mechanism such as TILFA that converts a sudden link or node failure into a non-urgent topology change by having complete repair path for all affected destinations. With microloop avoidance, the convergence will be slower compared to traditional (SPF) convergence mechanisms. So, when there is any failure of a link or a set of links that are not protected using an FRR mechanism, it is advised to use conventional SPF (faster) mode of operation to minimize packet loss during convergence/reconvergence.
Command Syntax
microloop-avoidance (level-1|level-2)
no microloop-avoidance (level-1|level-2)
Parameters
level-1
Level-1 only
level-2
Level-2 only
Defaults
N/A
Command Mode
ISIS router mode
Applicability
This command was introduced in OcNOS version 6.3.0.
Examples
#configure terminal
(config)#router isis 100
(config-router)#microloop-avoidance level-1
(config-router)#microloop-avoidance level-2
(config-router)#
#configure terminal
(config)#router isis 100
(config-router)#no microloop-avoidance level-1
(config-router)#no microloop-avoidance level-2
(config-router)#
microloop-avoidance hold-timer
Use this command to configure the hold-timer valuefor microloop avoidance.
Use the no form of this command to return to the default hold-timer value for microloop avoidance.
Hold-timer value means the time that router will wait after receiving first LSP update with a topology change, to group all related LSP updates together to process using oFIB.
Microloop avoidance has to be enabled first for the particular level before configuring the hold-timer.
Hold-timer value must be configured same across all routers in the network to get the desired results.
Command Syntax
microloop-avoidance hold-timer <1-60> (level-1|level-2)
no microloop-avoidance hold-timer (level-1|level-2)
Parameters
<1-60>
Hold-timer value in seconds
level-1
Level-1 only
level-2
Level-2 only
Defaults
Default value for hold-timer is 6 seconds
Command Mode
ISIS router mode
Applicability
This command was introduced in OcNOS version 6.3.0.
Examples
#configure terminal
(config)#router isis 100
(config-router)#microloop-avoidance hold-timer 3 level-1
(config-router)#microloop-avoidance hold-timer 3 level-2
(config-router)#
#configure terminal
(config)#router isis 100
(config-router)#no microloop-avoidance hold-timer level-1
(config-router)#no microloop-avoidance hold-timer level-2
(config-router)#
microloop-avoidance max-fib
Use this command to configure the max-fib value for microloop avoidance.
Use the no form of this command to return to the default max-fib value for microloop avoidance.
The max-fib value is a network-wide constant that reflects the maximum time required to update a FIB irrespective of the change required. This value will be further multiplied by the oFIB RANK to get the actual FIB update delay time.
Microloop avoidance has to be enabled first for the particular level before configuring max-fib.
Max-fib value must be configured same across all routers in the network to get the desired results.
Command Syntax
microloop-avoidance max-fib <1-60> (level-1|level-2)
no microloop-avoidance max-fib (level-1|level-2)
Parameters
<1-60>
Max-fib value in seconds
level-1
Level-1 only
level-2
Level-2 only
Defaults
Default value for max-fib is 2 seconds
Command Mode
ISIS router mode
Applicability
This command was introduced in OcNOS version 6.3.0.
Examples
#configure terminal
(config)#router isis 100
(config-router)#microloop-avoidance max-fib 3 level-1
(config-router)#microloop-avoidance max-fib 3 level-2
(config-router)#
#configure terminal
(config)#router isis 100
(config-router)#no microloop-avoidance max-fib level-1
(config-router)#no microloop-avoidance max-fib level-2
(config-router)#
show isis microloop-avoidance
Use this command to display microloop avoidance FSM states, timer values, and the oFIB route table.
Command Syntax
show isis microloop-avoidance (level-1|level-2|) (detail|)
Parameters
level-1
Display level-1 information only
level-2
Display level-2 information only
detail
Display detailed information for one or both levels
Command Mode
Privileged Exec mode
Applicability
This command was introduced in OcNOS version 6.3.0.
Example
PE1#sh isis microloop-avoidance
Tag 1: VRF : default
Level-1 status:
FSM State: OFIB_STABLE
Level-2 status:
FSM State: OFIB_STABLE
PE1#show isis microloop-avoidance detail
Tag 1: VRF : default
Level-1 status:
FSM State: OFIB_HOLDING_DOWN
Event type: Neighbor Down
Near end: 0000.0000.0001.00 Far end:0000.0000.0004.00
Hold-down timer running: Yes Time Remaining: 00:00:02.716
Delay timer running: No
Level-2 status:
FSM State: OFIB_STABLE
oFIB Route Table:
Destination Metric Next-Hop Interface Tag
L1 3.3.3.3/32 30 10.0.0.2 xe2 0
Src: 0000.0000.0003
L1 4.4.4.4/32 40 10.0.0.2 xe2 0
Src: 0000.0000.0004
L1 30.0.0.0/24 30 10.0.0.2 xe2 0
Src: 0000.0000.0003