DMVPN Phase 1, 2 & 3

NOTE

Phaseによる違い

Phase 1

  • Hubの負荷が高い
  • Spokeがトンネルを張るのはHubとだけ。Spoke間はHub折り返し。
  • Spoke のtunnel 設定の中で tunnel destination にHubを指定する。
  • Spoke では tunnel mode gre multipoint は利用しない。
  • Hub はtunnel mode gre multipointにする。
  • Hub折り返しなのでHubから経路を集約して出すことができる

 

 

Phase 2

  • Spokeが常時トンネルを張るのはHubとだけ。
  • 通信の必要が生じたら、Spokeと動的にトンネルを張って通信
  • Hub とSpoke は両方 tunnel mode gre multipointにする。
  • no ip next-hop-self eigrpでのhubにnexthop修正をさせないことでSpokeがSpoke宛を解決して直接通信しようとする
  • NHを解決するために一度はHubと通信が発生する
  • Phase 1と比べてHubの負荷が軽減できるが、Spokeが個別に経路をたくさん持ってしまう

 

Phase 3

  • NHRPのショートカットスイッチングを利用(ip nhrp shortcut)
  • Spoke間が動的にトンネルを張るのはPhase 2と同じだが、HubからSpokeに向けて集約経路を広報できる(Spokeの保持経路を減らせる)
  • 集約経路のNHがHubになるので一度Hub宛に通信するが、その後はNHがSpokeになるので直接通信する

 

 

R2#show ip route | b Gate
Gateway of last resort is not set

      10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
S        10.1.4.0/24 [1/0] via 10.2.4.4
C        10.2.4.0/24 is directly connected, FastEthernet0/0
L        10.2.4.2/32 is directly connected, FastEthernet0/0
S        10.3.4.0/24 [1/0] via 10.2.4.4
D     172.16.0.0/16 [90/28288000] via 192.168.123.1, 00:01:06, Tunnel0
D     192.168.1.0/24 [90/27008000] via 192.168.123.1, 00:01:06, Tunnel0
      192.168.2.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.2.0/24 is directly connected, Loopback0
L        192.168.2.2/32 is directly connected, Loopback0
D     192.168.3.0/24 [90/28288000] via 192.168.123.3, 00:01:06, Tunnel0
      192.168.123.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.123.0/24 is directly connected, Tunnel0
L        192.168.123.2/32 is directly connected, Tunnel0
R2#
R2#trace 172.16.10.3
Type escape sequence to abort.
Tracing the route to 172.16.10.3
VRF info: (vrf in name/id, vrf out name/id)
  1 192.168.123.1 60 msec 40 msec 32 msec
  2 192.168.123.3 56 msec 60 msec 24 msec
R2#trace 172.16.10.3
Type escape sequence to abort.
Tracing the route to 172.16.10.3
VRF info: (vrf in name/id, vrf out name/id)
  1 192.168.123.3 68 msec 40 msec 32 msec
R2#show ip route | b Gate
Gateway of last resort is not set

      10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
S        10.1.4.0/24 [1/0] via 10.2.4.4
C        10.2.4.0/24 is directly connected, FastEthernet0/0
L        10.2.4.2/32 is directly connected, FastEthernet0/0
S        10.3.4.0/24 [1/0] via 10.2.4.4
      172.16.0.0/16 is variably subnetted, 2 subnets, 2 masks
D        172.16.0.0/16 [90/28288000] via 192.168.123.1, 00:01:21, Tunnel0
H        172.16.10.0/24 [250/1] via 192.168.123.3, 00:00:07, Tunnel0
D     192.168.1.0/24 [90/27008000] via 192.168.123.1, 00:01:21, Tunnel0
      192.168.2.0/24 is variably subnetted, 2 subnets, 2 masks
C        192.168.2.0/24 is directly connected, Loopback0
L        192.168.2.2/32 is directly connected, Loopback0
D     192.168.3.0/24 [90/28288000] via 192.168.123.3, 00:01:21, Tunnel0
      192.168.123.0/24 is variably subnetted, 3 subnets, 2 masks
C        192.168.123.0/24 is directly connected, Tunnel0
L        192.168.123.2/32 is directly connected, Tunnel0
H        192.168.123.3/32 is directly connected, 00:00:07, Tunnel0
R2#

 

REFERENCE

Shortcut Switching Enhancements for NHRP in DMVPN Networks

Configure Phase-3 Hierarchical DMVPN with Multi-Subnet Spokes

 

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