IOS-XR passes on the attribute by default. Some other routers incorrectly claim it to be malformed and reset the BGP session. IOS-XR has a configuration to discard an attribute, so it will not pass it on. It will pass the route with all its other attributes. Here is an example configuration: router bgp {asn} attribute-filter group block_elc attribute 28 discard ! neighbor {ip address} update in filtering attribute-filter group block_elc ! ! ! More info: https://www.cisco.com/c/en/us/td/docs/routers/asr9000/software/routing/comma... https://www.cisco.com/c/en/us/td/docs/routers/asr9000/software/asr9k-r7-8/ro... Kind Regards, Jakob From: Jakob Heitz (jheitz) <jheitz@cisco.com> Date: Wednesday, August 30, 2023 at 7:43 AM To: nanog@nanog.org <nanog@nanog.org> Subject: Re: JunOS/FRR/Nokia et al BGP critical issue The blog was updated. Correct link: https://blog.benjojo.co.uk/post/bgp-path-attributes-grave-error-handling The attribute was not malformed. This is the hex dump of the attribute: “E0 1C 00” It is described here. https://www.rfc-editor.org/rfc/rfc6790#section-5.2 This attribute is deprecated, but that does not prevent routers from originating it or passing it on. Kind Regards, Jakob ----------------- Original message -------------- From: Mike Lyon <mike.lyon@gmail.com> To: NANOG list <nanog@nanog.org> Ran across this article today and haven't seen posts about it so i figured I would share: https://blog.benjojo.co.uk/post/bgp-path-attributes-grave-error-handling?fbclid=IwAR13ePY43Vf3u4X8PDyCDT39DtyXczAKkv6CGXOQbcQv90Y3aIAmTkJxn7k_aem_Ad0hzj2Mh_WlbFZug-vGdlJJdXr2Xo0RFIsPwAU2GviPz6xZDib76YHwFuzU7E0_sJk&mibextid=Zxz2cZ Curious if anyone on the list is running VyOS and has experienced any problems? Cheers, Mike -- Mike Lyon mike.lyon@gmail.com http://www.linkedin.com/in/mlyon