Customer observed the below errors coming continuously on their MX304 when connected via BGP to other Peers.

Router rpd[16763]: Malformed Attribute ELC(28) flag 0xc0 length 8 error 15 (Attribute is obsoleted).

Router rpd[16763]: Total incoming malformed attributes from x.x.x.x (Internal AS xxx) since last logging

Entropy Label Capability attribute (ELC) is an optional, transitive BGP path attribute that can be used to inform an LSP ingress router about an LSP egress router's ability to process entropy labels.

These logs are likely being generated because the sender is running an older version that still uses ELCv2. This syslog message is informational in nature and indicates that ELCv2 is now obsolete, with the newer ELCv3 (RCA/NHC) attributes recommended for use. This behavior is expected and does not indicate any issue.

To resolve this issue, we need to upgrade the peer router to version 23.3R1 or a later release as in the newer releases we have upgraded to ELCv3 so we would not receive these logs.