I was updating an internal distribution router that got wedged in vtysh from 8.5 to 8.5.2 and found all my ibgp peers would not come up. Same error on the half dozen peers Jun 29 14:00:55 ibgp-4 bgpd[38150]: [HZN6M-XRM1G] %NOTIFICATION: received from neighbor xx.yy.zz.251 3/4 (UPDATE Message Error/Attribute Flags Error) 14 bytes 80 1a 0b 01 00 0b 00 00 00 00 00 00 00 01 Jun 29 14:01:00 ibgp-4 bgpd[38150]: [HZN6M-XRM1G] %NOTIFICATION: received from neighbor xx.yy.zz.251 3/4 (UPDATE Message Error/Attribute Flags Error) 14 bytes 80 1a 0b 01 00 0b 00 00 00 00 00 00 00 01 Jun 29 14:01:05 ibgp-4 bgpd[38150]: [HZN6M-XRM1G] %NOTIFICATION: sent to neighbor xx.yy.zz.251 3/4 (UPDATE Message Error/Attribute Flags Error) 14 bytes c0 1a 0b 01 0 On the older versions of frr, [NYD0B-A3BTB][EC 33554433] AIGP attribute must be flagged as "Transitive" [HZN6M-XRM1G] %NOTIFICATION: sent to neighbor xx.yy.zz.241 3/4 (UPDATE Message Error/Attribute Flags Error) 14 bytes 80 1a 0b 01 0 [GW152-RVASS][EC 33554455] bgp_process_packet: BGP UPDATE receipt failed for peer: xx.yy.zz.241 I downgraded from 8.5.2 to 8.5.1 and all was good. Also, another peer thats still running 7.x was fine with it all. Nothing special about the config. One of the untouched boxes running 8.5 neighbor THOTLAN peer-group neighbor THOTLAN remote-as 11647 neighbor THOTLAN description Core1LanEx neighbor THOTLAN update-source [dot.251] neighbor .241 peer-group HOTLAN neighbor .241 description The box the flipped out neighbor .241 bfd neighbor THOTLAN activate neighbor THOTLAN next-hop-self neighbor THOTLAN weight 111 The box I tried to upgrade from 8.5 to 8.5.2 that then went back to 8.5.1 neighbor THOTLAN peer-group neighbor THOTLAN remote-as 11647 neighbor THOTLAN update-source [dot.241] neighbor THOTLAN timers 16 50 neighbor .251 description One of the many other peers that didnt like me neighbor .251 bfd neighbor THOTLAN activate neighbor THOTLAN next-hop-self neighbor THOTLAN soft-reconfiguration inbound neighbor THOTLAN weight 109 ---Mike