Всмысле стоимость очень высока для резерва? Главное чтобы выше чем у основного была, разе не так?

Схема такая:
A (Gi0/18) - DSL - (Fa0/24) B
A (Gi0/25) - FIBER - (Gi0/1) B
A (Gi0/1) - Gateway

IP адреса:
A (10.50.138.147)
B (10.50.138.249)
Gateway (10.50.138.129)

При работающих двух каналах:

A#sh spanning-tree vl 4

VLAN0004
  Spanning tree enabled protocol ieee
  Root ID    Priority    4100
             Address     64d9.89df.a200
             This bridge is the root
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    4100   (priority 4096 sys-id-ext 4)
             Address     64d9.89df.a200
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time  300 sec

Interface           Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Gi0/1               Desg FWD 4         128.1    P2p
Gi0/18              Desg FWD 19        128.18   P2p
Gi0/25              Desg FWD 4         128.25   P2p

Protocol  Address          Age (min)  Hardware Addr   Type   Interface
Internet  10.50.138.147           -   64d9.89df.a243  ARPA   Vlan4
Internet  10.50.138.129           0   ccef.4880.0481  ARPA   Vlan4
Internet  10.50.138.249           6   1c17.d388.dc41  ARPA   Vlan4

A#sh mac address-table address ccef.4880.0481
          Mac Address Table
-------------------------------------------

Vlan    Mac Address       Type        Ports
----    -----------       --------    -----
   2    ccef.4880.0481    DYNAMIC     Gi0/1
  10    ccef.4880.0481    DYNAMIC     Gi0/1
   4    ccef.4880.0481    DYNAMIC     Gi0/1
   3    ccef.4880.0481    DYNAMIC     Gi0/1
Total Mac Addresses for this criterion: 4

A#sh mac address-table address 1c17.d388.dc41
          Mac Address Table
-------------------------------------------

Vlan    Mac Address       Type        Ports
----    -----------       --------    -----
   4    1c17.d388.dc41    DYNAMIC     Gi0/25

  

B#sh spanning-tree vlan 4

VLAN0004
  Spanning tree enabled protocol ieee
  Root ID    Priority    4100
             Address     64d9.89df.a200
             Cost        4
             Port        25 (GigabitEthernet0/1)
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32772  (priority 32768 sys-id-ext 4)
             Address     1c17.d388.dc00
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time 300

Interface           Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Fa0/24              Altn BLK 19        128.24   P2p
Gi0/1               Root FWD 4         128.25   P2p

B#sh arp
Protocol  Address          Age (min)  Hardware Addr   Type   Interface
Internet  10.50.138.147           2   64d9.89df.a243  ARPA   Vlan4
Internet  10.50.138.129          67   ccef.4880.0481  ARPA   Vlan4
Internet  10.50.138.249           -   1c17.d388.dc41  ARPA   Vlan4

B#sh mac address-table address  ccef.4880.0481
          Mac Address Table
-------------------------------------------

Vlan    Mac Address       Type        Ports
----    -----------       --------    -----
   4    ccef.4880.0481    DYNAMIC     Gi0/1
Total Mac Addresses for this criterion: 1

B#sh mac address-table address  64d9.89df.a243
          Mac Address Table
-------------------------------------------

Vlan    Mac Address       Type        Ports
----    -----------       --------    -----
   4    64d9.89df.a243    DYNAMIC     Gi0/1
Total Mac Addresses for this criterion: 1

При обрыве оптики:

A#sh spanning-tree vl 4

VLAN0004
  Spanning tree enabled protocol ieee
  Root ID    Priority    4100
             Address     64d9.89df.a200
             This bridge is the root
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    4100   (priority 4096 sys-id-ext 4)
             Address     64d9.89df.a200
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time  300 sec

Interface           Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Gi0/18              Desg FWD 19        128.18   P2p

A#ping 10.50.138.129

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.50.138.129, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/3/6 ms

A#ping 10.50.138.249

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.50.138.249, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 5/6/10 ms

A#sh arp
Protocol  Address          Age (min)  Hardware Addr   Type   Interface
Internet  10.50.138.147           -   64d9.89df.a243  ARPA   Vlan4
Internet  10.50.138.129           6   ccef.4880.0481  ARPA   Vlan4
Internet  10.50.138.249          13   1c17.d388.dc41  ARPA   Vlan4

A#sh mac address-table  add 1c17.d388.dc41
          Mac Address Table
-------------------------------------------

Vlan    Mac Address       Type        Ports
----    -----------       --------    -----
   4    1c17.d388.dc41    DYNAMIC     Gi0/18
Total Mac Addresses for this criterion: 1

A#sh mac address-table  add  ccef.4880.0481
          Mac Address Table
-------------------------------------------

Vlan    Mac Address       Type        Ports
----    -----------       --------    -----
   2    ccef.4880.0481    DYNAMIC     Gi0/1
  10    ccef.4880.0481    DYNAMIC     Gi0/1
   4    ccef.4880.0481    DYNAMIC     Gi0/1
   3    ccef.4880.0481    DYNAMIC     Gi0/1
Total Mac Addresses for this criterion: 4

B#sh spanning-tree vl 4

VLAN0004
  Spanning tree enabled protocol ieee
  Root ID    Priority    4100
             Address     64d9.89df.a200
             Cost        19
             Port        24 (FastEthernet0/24)
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32772  (priority 32768 sys-id-ext 4)
             Address     1c17.d388.dc00
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time 15

Interface           Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Fa0/24              Root FWD 19        128.24   P2p

B#ping 10.50.138.147
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.50.138.147, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/7/9 ms

B#ping 10.50.138.129
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.50.138.129, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)

B#sh arp
Protocol  Address          Age (min)  Hardware Addr   Type   Interface
Internet  10.50.138.147           5   64d9.89df.a243  ARPA   Vlan4
Internet  10.50.138.129          70   ccef.4880.0481  ARPA   Vlan4
Internet  10.50.138.249           -   1c17.d388.dc41  ARPA   Vlan4

B#sh mac address-table add ccef.4880.0481
          Mac Address Table
-------------------------------------------

Vlan    Mac Address       Type        Ports
----    -----------       --------    -----
   4    ccef.4880.0481    DYNAMIC     Fa0/24
Total Mac Addresses for this criterion: 1

B#sh mac address-table add 64d9.89df.a243
          Mac Address Table
-------------------------------------------

Vlan    Mac Address       Type        Ports
----    -----------       --------    -----
   4    64d9.89df.a243    DYNAMIC     Fa0/24
Total Mac Addresses for this criterion: 1