Segment
Routing—IS-IS v4 node SID
The Segment Routing—ISIS v4 node SID feature provides support for segment routing on Cisco Intermediate System-to-Intermediate System (IS-IS) networks.
- Information About Segment Routing IS-IS v4 Node SID
- How to Configure Segment Routing —IS-IS v4 Node SID
- Configuration Examples for Segment Routing —IS-IS v4 Node SID
- Additional References for Segment Routing-IS-IS v4 Node SID
- Feature Information for Segment Routing—IS-IS v4 Node SID
Information About Segment Routing IS-IS v4 Node SID
Segment Routing IS-IS v4 Node SID
Segment Routing (SR) is a technique by which the path followed by a packet is encoded in the packet itself. The path followed by a packet in segment routing is encoded in the packet itself similar to loose or strict source routing. Segment Routing relies on a small number of extensions to Cisco Intermediate System-to-Intermediate System (IS-IS) and Open Shortest Path First (OSPF) protocols.
How to Configure Segment Routing —IS-IS v4 Node SID
Configuring Segment Routing
Before configuring IS-IS to support segment routing you must first configure the segment routing feature in global configuration mode.
1.
enable
2.
configure
terminal
3. segment-routing mpls
4. connected-prefix-sid-map
5. address-family ipv4
6. 1.1.1.1/32 index 100 range 1
7. exit-address-family
DETAILED STEPS
Configuring Segment Routing on IS-IS Network
Before you configure segment routing on IS-IS network, IS-IS must be enabled on your network.
1. router isis
2. net network-entity-title
3. metric-style wide
4. segment-routing mpls
5. exit
6. show isis segment-routing
DETAILED STEPS
The following example displays output from the show isis segment-routing state command for the segment routing under IS-IS:
Device# show isis segment-routing ISIS protocol is registered with MFI ISIS MFI Client ID:0x63 Tag 1 - Segment-Routing: SR State:SR_ENABLED Number of SRGB:1 SRGB Start:16000, Range:8000, srgb_handle:0x4500AED0, srgb_state: created Address-family IPv4 unicast SR is configured Operational state:Enabled
Configuring Prefix-SID for IS-IS
This task explains how to configure prefix segment identifier (SID) index under each interface.
Segment routing must be enabled on the corresponding address family.
1. enable
2. configure terminal
3.
segment-routing
mpls
4.
connected-prefix-sid-map
5.
address-family ipv4
6. 1.1.1.1/32 index 100 range 1
7. exit
DETAILED STEPS
Configuring Prefix Attribute N-flag-clear
By default, a flag called N-flag is set by IS-IS when advertising a SID which is associated with a loopback address. If you wish to clear this flag add explicit configuration.
1.
enable
2.
configure
terminal
3. interface loopback3
4. isis prefix n-flag-clear
DETAILED STEPS
Configuring Explicit Null Attribute
To disable penultimate-hop-popping (PHP) and add explicit-Null label, explicit-null option needs to be specified. Once the option is given, IS-IS sets the E flag in the prefix-SID sub TLV.
By default, a flag called E-flag (Explicit-Null flag) is set to 0 by ISIS when advertising a Prefix SID which is associated with a loopback address. If you wish to set this flag add explicit configuration
1.
enable
2.
configure
terminal
3. segment-routing mpls
4. set-attributes
5.
address-family ipv4
6.
explicit-null
7.
exit-address-family
DETAILED STEPS
Configuration Examples for Segment Routing —IS-IS v4 Node SID
Example: Configuring Segment Routing on IS-IS Network
The following example shows how to configure prefix segment identifier (SID) index under each interface:
Device(config)#segment-routing mpls Device(config-srmpls)#connected-prefix-sid-map Device(config-srmpls-conn)#address-family ipv4 Device(config-srmpls-conn-af)#10.1.2.2/32 index 2 range 1 Device(config-srmpls-conn-af)#exit-address-family Device(config-srmpls-conn-af)#end
Example: Configuring Explicit Null Attribute
The following is an example for configuring explicit null attribute:
Device(config)# segment-routing mpls Device(config-srmpls)# set-attributes Device(config-srmpls-attr)# address-family ipv4 Device(config-srmpls-attr-af)# explicit-null Device (config-srmpls-attr-af)# exit-address-family
Additional References for Segment Routing-IS-IS v4 Node SID
Related Documents
Related Topic |
Document Title |
---|---|
Cisco IOS commands |
Cisco IOS Master Command List, All Releases http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/mcl/allreleasemcl/all-book.html |
IP Routing ISIS commands |
Cisco IOS IP Routing ISIS commands http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/mcl/allreleasemcl/all-book.html |
Technical Assistance
Description |
Link |
---|---|
The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password. |
Feature Information for Segment Routing—IS-IS v4 Node SID
Feature Name |
Releases |
Feature Information |
---|---|---|
Segment Routing—IS-IS v4 Node SID |
Cisco IOS XE Release 3.16S |
The Segment Routing—ISIS v4 node SID feature provides support for segment routing on IS-IS networks. The following commands were introduced or modified: connected-prefix-sid-map, show isis segment-routing, isis prefix n-flag-clear, explicit-null |