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@myomyomyo

NETCON(JANOG57) Level3-1 解いてみた

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Last updated at Posted at 2026-02-14

はじめに

NETCON(JANOG57) Level3-1の問題を解いた過程を記録します。
JANOG期間が終わった週末にも問題を公開頂いてありがたい限りです！！

1. Loopbackへの到達性確認

  • LeafのLoからSpineのLoまでPingが通らない
RT-L-01#ping 10.1.254.11 source 10.1.254.21
PING 10.1.254.11 (10.1.254.11) from 10.1.254.21 : 72(100) bytes of data.

^C
--- 10.1.254.11 ping statistics ---
5 packets transmitted, 0 received, 100% packet loss, time 40ms

RT-L-01#
RT-L-01#ping 10.1.254.22 source 10.1.254.21
PING 10.1.254.22 (10.1.254.22) from 10.1.254.21 : 72(100) bytes of data.
80 bytes from 10.1.254.22: icmp_seq=1 ttl=64 time=2.22 ms
80 bytes from 10.1.254.22: icmp_seq=2 ttl=64 time=1.68 ms
80 bytes from 10.1.254.22: icmp_seq=3 ttl=64 time=1.69 ms
80 bytes from 10.1.254.22: icmp_seq=4 ttl=64 time=1.20 ms
80 bytes from 10.1.254.22: icmp_seq=5 ttl=64 time=1.29 ms

--- 10.1.254.22 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 8ms
rtt min/avg/max/mdev = 1.201/1.613/2.218/0.361 ms, ipg/ewma 2.078/1.894 ms
RT-L-01#

2.ルーティングテーブルの確認

  • SpineのLo宛経路が存在しない
RT-L-01#show ip route

Gateway of last resort is not set

 C        10.1.254.21/32 [0/0]
           via Loopback0, directly connected
 B E      10.1.254.22/32 [200/0]
           via fe80::a8c1:abff:fe30:8b16, Ethernet1

RT-L-01#

3.SpineのBGP状態を確認

  • 自分のLoアドレスを広報していない
          Network                Next Hop              Metric  AIGP       LocPref Weight  Path
 * >      10.1.254.21/32         fe80::a8c1:abff:fe86:58b%Et1 0       -          100     0       65201 i
 * >      10.1.254.22/32         fe80::a8c1:abff:fecd:b2d%Et2 0       -          100     0       65202 i
RT-S-01#

4.SpineのBGP設定を確認

  • networkコマンドで広報する設定にはなっている
  • route-mapが怪しそうと思ったけど間違っていない
  • Claudeに聞いてみるとnetworkコマンドで指定しているPrefixが間違っていると気づく
  • 修正してみたけどSV-01からPingは相変わらず通らない
RT-S-01#show run | sec bgp
router bgp 65100
   router-id 10.1.254.11
   no bgp default ipv4-unicast
   bgp default ipv4-unicast transport ipv6
   bgp listen range 10.1.254.0/24 peer-group EVPN peer-filter ALLOW-ASN
   neighbor EVPN peer group
   neighbor EVPN update-source Loopback0
   neighbor EVPN ebgp-multihop
   neighbor LEAF peer group
   neighbor LEAF bfd
   neighbor interface Et1-2 peer-group LEAF peer-filter ALLOW-ASN
   !
   address-family evpn
      neighbor EVPN activate
   !
   address-family ipv4
      neighbor LEAF activate
      neighbor LEAF route-map ACCEPT_PREFIX_LOOPBACK in
      neighbor LEAF route-map ACCEPT_PREFIX_LOOPBACK out
      neighbor LEAF next-hop address-family ipv6 originate
      network 10.1.255.11/32
RT-S-01#

5. Leafのevpn状態を確認

  • mac-ipは学習できていそう
  • EVPNのNeighborがEstablishしていないのでこれが原因ぽい
RT-L-01#show bgp evpn
BGP routing table information for VRF default
Router identifier 10.1.254.21, local AS number 65201
Route status codes: * - valid, > - active, S - Stale, E - ECMP head, e - ECMP
                    c - Contributing to ECMP, % - Pending best path selection
Origin codes: i - IGP, e - EGP, ? - incomplete
AS Path Attributes: Or-ID - Originator ID, C-LST - Cluster List, LL Nexthop - Link Local Nexthop

          Network                Next Hop              Metric  LocPref Weight  Path
 * >      RD: 10.1.254.21:1010 mac-ip aabb.cc10.1001
                                 -                     -       -       0       i
 * >      RD: 10.1.254.21:1010 imet 10.1.254.21
                                 -                     -       -       0       i
RT-L-01#
RT-L-01#show bgp evpn summary
BGP summary information for VRF default
Router identifier 10.1.254.21, local AS number 65201
Neighbor Status Codes: m - Under maintenance
  Neighbor    V AS           MsgRcvd   MsgSent  InQ OutQ  Up/Down State   PfxRcd PfxAcc PfxAdv
  10.1.254.11 4 65100              0         0    0    0 23:19:29 Idle(NoIf)
RT-L-01#

6.LeafのBGP設定を再度確認

  • SpineのConfigと見比べてみるとebgp-multihopの設定が足りていない
  • オーバーレイのBGPはeBGPのLoopback同士でネイバーを張るためmultihopの設定が必須
  • 設定を入れるとネイバーがEstablishとなった！
RT-L-01#show run | sec bgp
router bgp 65201
   router-id 10.1.254.21
   no bgp default ipv4-unicast
   bgp default ipv4-unicast transport ipv6
   neighbor EVPN peer group
   neighbor EVPN remote-as 65100
   neighbor EVPN update-source Loopback0
   neighbor EVPN ebgp-multihop
   neighbor EVPN send-community extended
   neighbor SPINE peer group
   neighbor SPINE remote-as 65100
   neighbor SPINE bfd
   neighbor 10.1.254.11 peer group EVPN
   neighbor interface Et1 peer-group SPINE
   !
   vlan 10
      rd 10.1.254.21:1010
      route-target both 10:1010
      redistribute learned
   !
   address-family evpn
      neighbor EVPN activate
   !
   address-family ipv4
      neighbor SPINE activate
      neighbor SPINE route-map ACCEPT_PREFIX_LOOPBACK in
      neighbor SPINE route-map ACCEPT_PREFIX_LOOPBACK out
      neighbor SPINE next-hop address-family ipv6 originate
      network 10.1.254.21/32
RT-L-01#
RT-L-01#show bgp evpn summary
BGP summary information for VRF default
Router identifier 10.1.254.21, local AS number 65201
Neighbor Status Codes: m - Under maintenance
  Neighbor    V AS           MsgRcvd   MsgSent  InQ OutQ  Up/Down State   PfxRcd PfxAcc PfxAdv
  10.1.254.11 4 65100             15        15    0    0 00:03:16 Estab   1      1      1
RT-L-01#

7.SV-01からSV-02へ通信流してみる

  • これで解決！と思ったもののPingは通らず...

8.もう一度Leafの状態を確認

  • EVPNでmac-ipは学習できていそう
  • ただVXLANにMACアドレスがのっていない...
  • 手詰まりだったのでClaudeに聞いてみると、SpineでExtended Communityを転送していないことが判明
RT-L-01#show bgp evpn
BGP routing table information for VRF default
Router identifier 10.1.254.21, local AS number 65201
Route status codes: * - valid, > - active, S - Stale, E - ECMP head, e - ECMP
                    c - Contributing to ECMP, % - Pending best path selection
Origin codes: i - IGP, e - EGP, ? - incomplete
AS Path Attributes: Or-ID - Originator ID, C-LST - Cluster List, LL Nexthop - Link Local Nexthop

          Network                Next Hop              Metric  LocPref Weight  Path
 * >      RD: 10.1.254.21:1010 mac-ip aabb.cc10.1001
                                 -                     -       -       0       i
 * >      RD: 10.1.254.22:1010 mac-ip aabb.cc10.1002
                                 10.1.254.22           -       100     0       65100 65202 i
 * >      RD: 10.1.254.21:1010 imet 10.1.254.21
                                 -                     -       -       0       i
 * >      RD: 10.1.254.22:1010 imet 10.1.254.22
                                 10.1.254.22           -       100     0       65100 65202 i
RT-L-01#

RT-L-01#show vxlan address-table
          Vxlan Mac Address Table
----------------------------------------------------------------------

VLAN  Mac Address     Type      Prt  VTEP             Moves   Last Move
----  -----------     ----      ---  ----             -----   ---------
Total Remote Mac Addresses for this criterion: 0
RT-L-01#

9.Spineの設定を変更

  • SpineにExtended Communityを転送する設定を投入
  • すると無事にSV-01からSV-02に通信することができた！
SV-01:~# ping 192.168.10.2
PING 192.168.10.2 (192.168.10.2) 56(84) bytes of data.
64 bytes from 192.168.10.2: icmp_seq=1 ttl=64 time=9.56 ms
64 bytes from 192.168.10.2: icmp_seq=2 ttl=64 time=4.06 ms
64 bytes from 192.168.10.2: icmp_seq=3 ttl=64 time=4.31 ms
^C
--- 192.168.10.2 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2002ms
rtt min/avg/max/mdev = 4.060/5.979/9.564/2.536 ms
SV-01:~#

10.おさらい

  • SpineにExtended Community設定が入っていない場合
  • Leafから通知するルートにはExtended Community: Route-Target-AS:10:1010 TunnelEncap:tunnelTypeVxlanの記載があるが、Spineを経由して通知されるルートにはExtended Communityの記載がない
RT-L-01#show bgp evpn detail
BGP routing table information for VRF default
Router identifier 10.1.254.21, local AS number 65201
BGP routing table entry for mac-ip aabb.cc10.1001, Route Distinguisher: 10.1.254.21:1010
 Paths: 1 available
  Local
    - from - (0.0.0.0)
      Origin IGP, metric -, localpref -, weight 0, tag 0, valid, local, best
      Extended Community: Route-Target-AS:10:1010 TunnelEncap:tunnelTypeVxlan
      VNI: 1010 ESI: 0000:0000:0000:0000:0000
BGP routing table entry for mac-ip aabb.cc10.1002, Route Distinguisher: 10.1.254.22:1010
 Paths: 1 available
  65100 65202
    10.1.254.22 from 10.1.254.11 (10.1.254.11)
      Origin IGP, metric -, localpref 100, weight 0, tag 0, valid, external, best
      VNI: 1010 ESI: 0000:0000:0000:0000:0000
BGP routing table entry for imet 10.1.254.21, Route Distinguisher: 10.1.254.21:1010
 Paths: 1 available
  Local
    - from - (0.0.0.0)
      Origin IGP, metric -, localpref -, weight 0, tag 0, valid, local, best
      Extended Community: Route-Target-AS:10:1010 TunnelEncap:tunnelTypeVxlan
      VNI: 1010
      PMSI Tunnel: Ingress Replication, MPLS Label: 1010, Leaf Information Required: false, Tunnel ID: 10.1.254.21
BGP routing table entry for imet 10.1.254.22, Route Distinguisher: 10.1.254.22:1010
 Paths: 1 available
  65100 65202
    10.1.254.22 from 10.1.254.11 (10.1.254.11)
      Origin IGP, metric -, localpref 100, weight 0, tag 0, valid, external, best
      VNI: 1010
      PMSI Tunnel: Ingress Replication, MPLS Label: 1010, Leaf Information Required: false, Tunnel ID: 10.1.254.22
RT-L-01#
  • SpineにExtended community設定を入れた場合
  • Spineを経由して通知されたルートにもExtended Communityの記載がある
RT-L-01#show bgp evpn detail
BGP routing table information for VRF default
Router identifier 10.1.254.21, local AS number 65201
BGP routing table entry for mac-ip aabb.cc10.1001, Route Distinguisher: 10.1.254.21:1010
 Paths: 1 available
  Local
    - from - (0.0.0.0)
      Origin IGP, metric -, localpref -, weight 0, tag 0, valid, local, best
      Extended Community: Route-Target-AS:10:1010 TunnelEncap:tunnelTypeVxlan
      VNI: 1010 ESI: 0000:0000:0000:0000:0000
BGP routing table entry for mac-ip aabb.cc10.1002, Route Distinguisher: 10.1.254.22:1010
 Paths: 1 available
  65100 65202
    10.1.254.22 from 10.1.254.11 (10.1.254.11)
      Origin IGP, metric -, localpref 100, weight 0, tag 0, valid, external, best
      Extended Community: Route-Target-AS:10:1010 TunnelEncap:tunnelTypeVxlan
      VNI: 1010 ESI: 0000:0000:0000:0000:0000
BGP routing table entry for imet 10.1.254.21, Route Distinguisher: 10.1.254.21:1010
 Paths: 1 available
  Local
    - from - (0.0.0.0)
      Origin IGP, metric -, localpref -, weight 0, tag 0, valid, local, best
      Extended Community: Route-Target-AS:10:1010 TunnelEncap:tunnelTypeVxlan
      VNI: 1010
      PMSI Tunnel: Ingress Replication, MPLS Label: 1010, Leaf Information Required: false, Tunnel ID: 10.1.254.21
BGP routing table entry for imet 10.1.254.22, Route Distinguisher: 10.1.254.22:1010
 Paths: 1 available
  65100 65202
    10.1.254.22 from 10.1.254.11 (10.1.254.11)
      Origin IGP, metric -, localpref 100, weight 0, tag 0, valid, external, best
      Extended Community: Route-Target-AS:10:1010 TunnelEncap:tunnelTypeVxlan
      VNI: 1010
      PMSI Tunnel: Ingress Replication, MPLS Label: 1010, Leaf Information Required: false, Tunnel ID: 10.1.254.22
RT-L-01#
  • VXLANもVTEPを通じてMACアドレスを学習できている
RT-L-01#show vxlan address-table
          Vxlan Mac Address Table
----------------------------------------------------------------------

VLAN  Mac Address     Type      Prt  VTEP             Moves   Last Move
----  -----------     ----      ---  ----             -----   ---------
  10  aabb.cc10.1002  EVPN      Vx1  10.1.254.22      1       0:00:55 ago
Total Remote Mac Addresses for this criterion: 1
RT-L-01#

参考

答え合わせとして以下の記事を参考にさせて頂きました、ありがとうございます。
JANOG57 NETCON Level3-1 問題解説 - Zenn

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