zebra で BGP経路を受けてみる

zebra にパッチを当てる
最初、BGP peer 自体が上がらず、随分苦労しました。
debug をかけると、BGP のセッションを上げる際の OPEN メッセージのやりとりの部分で Capability 周りのネゴでミスっているような雰囲気なのは分かったんですが・・。


2004/03/14 02:29:05 BGP: 2001:470:1f00:ffff::160 went from Active to OpenSent
2004/03/14 02:29:05 BGP: 2001:470:1f00:ffff::160 rcv message type 1, length (excl. header) 26
2004/03/14 02:29:05 BGP: 2001:470:1f00:ffff::160 rcv OPEN, version 4, remote-as 6939, holdtime 180, id 64.71.128.82
2004/03/14 02:29:05 BGP: 2001:470:1f00:ffff::160 sending OPEN, version 4, my as 65534, holdtime 180, id 210.155.223.41
2004/03/14 02:29:05 BGP: 2001:470:1f00:ffff::160 send message type 1, length (incl. header) 29
2004/03/14 02:29:05 BGP: 2001:470:1f00:ffff::160 rcv OPEN w/ OPTION parameter len: 16
2004/03/14 02:29:05 BGP: 2001:470:1f00:ffff::160 rcvd OPEN w/ optional parameter type 2 (Capability) len 6
2004/03/14 02:29:05 BGP: 2001:470:1f00:ffff::160 OPEN has CAPABILITY code: 1, length 4
2004/03/14 02:29:05 BGP: 2001:470:1f00:ffff::160 OPEN has MP_EXT CAP for afi/safi: 2/1
2004/03/14 02:29:05 BGP: 2001:470:1f00:ffff::160 rcvd OPEN w/ optional parameter type 2 (Capability) len 2
2004/03/14 02:29:05 BGP: 2001:470:1f00:ffff::160 OPEN has CAPABILITY code: 128, length 0
2004/03/14 02:29:05 BGP: 2001:470:1f00:ffff::160 OPEN has ROUTE-REFRESH capability(old) for all address-families
2004/03/14 02:29:05 BGP: 2001:470:1f00:ffff::160 rcvd OPEN w/ optional parameter type 2 (Capability) len 2
2004/03/14 02:29:05 BGP: 2001:470:1f00:ffff::160 OPEN has CAPABILITY code: 2, length 0
2004/03/14 02:29:05 BGP: 2001:470:1f00:ffff::160 OPEN has ROUTE-REFRESH capability(new) for all address-families
2004/03/14 02:29:05 BGP: 2001:470:1f00:ffff::160 went from OpenSent to OpenConfirm
2004/03/14 02:29:05 BGP: 2001:470:1f00:ffff::160 send message type 4, length (incl. header) 19
2004/03/14 02:29:05 BGP: 2001:470:1f00:ffff::160 rcv message type 3, length (excl. header) 2
2004/03/14 02:29:05 BGP: 2001:470:1f00:ffff::160 received NOTIFICATION 2/7 (OPEN Message Error/Unsupported Capability.) 0 bytes
2004/03/14 02:29:05 BGP: 2001:470:1f00:ffff::160 went from OpenConfirm to Idle

結局、いろいろ調査・トライした結果、zebra の bgpd 自体にこんなパッチを当てることで peer が上がるようになりました。


% diff -u1 bgp_packet.c.org bgp_packet.c
--- bgp_packet.c.org    Wed Nov  5 03:00:42 2003
+++ bgp_packet.c        Sun Mar 14 03:42:14 2004
@@ -761,3 +761,5 @@
   /* Set capability code. */
-  bgp_open_capability (s, peer);
+  if (CHECK_FLAG (peer->sflags, PEER_STATUS_CAPABILITY_OPEN) &&
+     ! CHECK_FLAG (peer->flags, PEER_FLAG_DONT_CAPABILITY))
+    bgp_open_capability (s, peer);

参考: [zebra 15310] Re: Zebra 0.93a has lost BGP interoperability with gated-3.6.0 (public)
※これが本質的で確実な解決策なのかどうかは分からないので試す場合は自己責任で。

【BGP peer の状態 (show bgp neighbor)】


vogue-bgpd> sh bgp n 2001:470:1f00:ffff::160
BGP neighbor is 2001:470:1f00:ffff::160, remote AS 6939, local AS 65534, external link
  BGP version 4, remote router ID 64.71.128.82
  BGP state = Established, up for 08:04:09
  Last read 00:00:08, hold time is 180, keepalive interval is 60 seconds
  Neighbor capabilities:
    Route refresh: advertised and received (old and new)
    Address family IPv6 Unicast: advertised and received
  Received 1022 messages, 0 notifications, 0 in queue
  Sent 487 messages, 0 notifications, 0 in queue
  Route refresh request: received 0, sent 0
  Minimum time between advertisement runs is 30 seconds

 For address family: IPv6 Unicast
  Inbound soft reconfiguration allowed
  Community attribute sent to this neighbor (both)
  Inbound path policy configured
  Outbound path policy configured
  Incoming update prefix filter list is *PREFIXLEN
  Outgoing update network filter list is *all-deny
  425 accepted prefixes

  Connections established 1; dropped 0
  Last reset never
Local host: 2001:470:1f00:ffff::161, Local port: 2037
Foreign host: 2001:470:1f00:ffff::160, Foreign port: 179
Nexthop: 210.155.223.41
Nexthop global: 2001:470:1f00:ffff::161
Nexthop local: ::
BGP connection: non shared network
Read thread: on  Write thread: off

マルチホームもどきをやってみる
実は、別の某社からも Full route を受けているので、マルチホームもどきの状態になっています。
bgpdのコンフィグレーションと現在の経路はBGP4+ 的に見た IPv6 Internet の姿（経路数統計・経路詳細）を参照。

※もし、ピアリング遊びをしたい方がいらっしゃいましたらご連絡ください。