Related Documentation
- J, SRX Series
- Example: Configuring IS-IS for CLNS
- J, MX, SRX Series
- Example: Configuring Static Routes for CLNS
- Example: Configuring BGP and CLNS
clns-updown-compatibility
Syntax
Hierarchy Level
Release Information
Statement introduced in Junos OS Release 11.4R7.
Description
When you enable IS-IS to exchange Connectionless Network Service (CLNS) routes, Junos OS sets the reserved (R) bit in the default metric field inside type, length, and value (TLV) type-3 (ES-Neighbor) as a marker for routing loop prevention. Junos OS uses the up/down bit for marking prefixes on the Level 2-to-Level 1 boundary as being propagated Down, such that any router in that area never propagates it Up on a Level 1-to-Level 2 boundary. For detailed information about how this works in IP routing environments, see RFC 2966, Domain-wide Prefix Distribution with Two-Level IS-IS.
Some other vendors’ platforms might not support up/down bit setting in CLNS route TLVs. If one of these vendors’ platforms receives this TLV with the R bit set, the platform discards the information.
When you use the clns-updown-compatibility statement in the IS-IS configuration, the R bit is set to 0, and the issue is resolved. The clns-updown-compatibility statement causes Junos OS to use the Internal/External metric-type bit in the TLV header instead of using the R bit as the up/down bit marker. This has the advantage that older end system (ES) equipment does not receive TLV headers with the R bit set.
![]() | Caution: Not using the R bit can lead to potential routing loops. You can use the site-of-origin (SoO) extended community to prevent a looped BGP update from being injected back to IS-IS when received from a remote provider edge (PE) device. The receiving PE device can check against the SoO community, and if the value matches its own, the NLRI is not accepted. |
Required Privilege Level
routing—To view this statement in the configuration.
routing-control—To add this statement to the configuration.
Related Documentation
- J, SRX Series
- Example: Configuring IS-IS for CLNS
- J, MX, SRX Series
- Example: Configuring Static Routes for CLNS
- Example: Configuring BGP and CLNS
Published: 2013-07-22
Related Documentation
- J, SRX Series
- Example: Configuring IS-IS for CLNS
- J, MX, SRX Series
- Example: Configuring Static Routes for CLNS
- Example: Configuring BGP and CLNS