Configuring Flexible Algorithm for Segment Routing Traffic Engineering
Before you begin configuring the flexible algorithm for IS-IS, make sure you:
-
Configure the device interfaces to enable IP transport.
-
Configure IS-IS protocol to enable dynamic routing protocol to exchange routing information.
-
Configure BGP protocol.
-
Configure segment routing.
To configure flexible algorithm for IS-IS:
- Define flexible algorithm on routers that you have identified
in your network. Assign
an
ID
for the flexible algorithm definition (FAD) ranging from 128
through 255.
[edit routing-options] user@host# set flex-algorithm id
Note:We recommend configuring flexible algorithm on only a few routers to provide redundancy and to avoid conflicts.
Specify the parameters of the definition. IS-IS calculates the path based on these specified parameters of the FAD.
- Map a BGP color community to the defined FAD.
By default each flexible algorithm is associated
with a value equal to the flex algorithm.
VPN can be made to resolve paths over the configured BGP color community.
[edit routing-options flex-algorithm id]user@host# set color desired color community valueNote:Changing the BGP color community for a flexible algorithm might result in traffic disruption. If you modify a BGP color community for a flexible algorithm then all routes pertaining to that flexible algorithm are removed from the RIB and added again with new colors.
- Specify the calculation type based on which the
IS-IS protocol calculates the path.
[edit routing-options flex-algorithm id definition] user@host# set (spf | strict-spf)
- Specify the metric type based on which IS-IS
calculates the path.
[edit routing-options flex-algorithm id definition] user@host# set metric-type (delay-metric | igp-metric | te-metric)
- Assign a priority level to the advertisement of
the FAD based on your requirement. Specify a
priority ranging from 0 through 255.
[edit routing-options flex-algorithm id definition] user@host# set priority priority
Note:Modifying the flexible algorithm definition could cause traffic disruptions until all the nodes converge on the new paths.
- If you have enabled RSVP traffic engineering,
you can configure admin-groups for many protocols
to color an individual link.
[edit protocols mpls]user@host# set admin-groups - Define the admin groups as per your
requirement.
[edit routing-options flex-algorithm definition admin-group]user@host# set include any admin-group user@host# set include-all admin-group user@host# set exclude admin-groupNote:For FADs with link-constraints to work, all relevant links should advertise the admin-colors in IS-IS. You must either enable RSVP on the interfaces or if you have not configured RSVP for traffic engineering, make sure you configure
set traffic-engineering advertise alwaysat the[edit protocols isis]hierarchy level.
- Map a BGP color community to the defined FAD.
By default each flexible algorithm is associated
with a value equal to the flex algorithm.
- Identify the participating routers and configure participation
on those routers. The same device can advertise a FAD and
also participate in a flexible algorithm.
[edit protocols isis source-packet-routing]user@host# set flex-algorithm id - Advertise prefix segments through policy configuration.
[edit policy-options policy-statement name term name]user@host# set from route-filter route exact user@host# set then prefix-segment algorithm id index value user@host# set then prefix-segment algorithm id node-segment - Apply the policy under the protocol IS-IS.
[edit protocols isis]user@host# set export name - To verify if your flexible algorithm configuration is working
correctly use the
show isis spring flex-algorithmcommand.