I am trying to set up BGP peering with a route-server, concurrently dual-stack. BGP 4 over an IPv4 connection works fine. A separate BGP 6 over IPv6 fails: with an "[Error] No common capability". I am using quagga 0.99.20 on ubuntu 10.04.03. I don't know what the route-server is. I have tried to tell both quagga to not be strict about capabilities or not negotiate them at all. My quagga config includes: router bgp XX no bgp enforce-first-as no bgp default ipv4-unicast !! tried with and without this bgp router-id XX network XY/24 route-map SetAttr neighbor XX4 remote-as XX neighbor XX4 activate neighbor XX4 next-hop-self neighbor XX4 send-community address-family ipv6 network XY6/48 route-map SetAttr neighbor XX6 remote-as XX neighbor XX6 activate neighbor XX6 next-hop-self neighbor XX6 send-community neighbor XX6 soft-reconfiguration inbound The code, I think, that's triggering the error is: /* Check there is no common capability send Unsupported Capability error. */ if (*capability && ! CHECK_FLAG (peer->flags, PEER_FLAG_OVERRIDE_CAPABILITY)) { if (! peer->afc_nego[AFI_IP][SAFI_UNICAST] && ! peer->afc_nego[AFI_IP][SAFI_MULTICAST] && ! peer->afc_nego[AFI_IP][SAFI_MPLS_VPN] && ! peer->afc_nego[AFI_IP6][SAFI_UNICAST] && ! peer->afc_nego[AFI_IP6][SAFI_MULTICAST]) From tcpdump, my side's open message includes: Open Message (1), length: 57 Version 4, my AS XX, Holdtime 180s, ID XX4 !! XX4 is my V4 address Optional parameters, length: 28 Option Capabilities Advertisement (2), length: 6 Multiprotocol Extensions (1), length: 4 AFI IPv4 (1), SAFI Unicast (1) 0x0000: 0001 0001 Option Capabilities Advertisement (2), length: 2 Route Refresh (Cisco) (128), length: 0 Option Capabilities Advertisement (2), length: 2 Route Refresh (2), length: 0 Option Capabilities Advertisement (2), length: 6 32-Bit AS Number (65), length: 4 no decoder for Capability 65 0x0000: 0000 e0c5 Option Capabilities Advertisement (2), length: 2 Unknown (66), length: 0 no decoder for Capability 66 The route-server's response is: Open Message (1), length: 45 Version 4, my AS XX, Holdtime 240s, ID XY4 !! XY4 is his V4 address Optional parameters, length: 16 Option Capabilities Advertisement (2), length: 14 Multiprotocol Extensions (1), length: 4 AFI IPv6 (2), SAFI Unicast (1) 0x0000: 0002 0001 To which I respond: Notification Message (3), length: 27, OPEN Message Error (2), subcode Capability Message Error (7) When I add "dont-capability-negotiate" to the config, I send: Open Message (1), length: 29 Version 4, my AS 57541, Holdtime 180s, ID XX4 Optional parameters, length: 0 I get back: Open Message (1), length: 45 Version 4, my AS XX, Holdtime 240s, ID XY4 Optional parameters, length: 16 Option Capabilities Advertisement (2), length: 14 Multiprotocol Extensions (1), length: 4 AFI IPv6 (2), SAFI Unicast (1) 0x0000: 0002 0001 I respond: Notification Message (3), length: 27, OPEN Message Error (2), subcode Capability Message Error (7) I'm a developer and former rfc writer, not a network operator. thanks nanog, -- David Waitzman BBN Technologies