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HSRP の Src Mac は Active = VMAC、Standby = Real MAC で Hello する

CML2 上の Cisco IOS で試したところ、HSRP v1 で Hello パケットの交換を行う際、送信元 MAC アドレスは以下になっていました。

HSRP State Src MAC Address
Active HSRP VMAC を利用する
Standby Real MAC を利用する

検証構成

CML2 上に以下の構成を作成して検証を行いました。

file

CML2 用のトポロジーは下記にアップロードしてあります。

検証環境の MAC アドレス

HSRP を構成している IOSvL2 の MAC アドレス一覧は以下の通りです。

Interface IOSvL2-1 IOSvL2-2
GigabitEthernet0/0 5254.0014.89fe 5254.0017.b51e
GigabitEthernet0/1 5254.0007.df55 5254.0006.4a86
GigabitEthernet0/2 5254.0017.e149 5254.0013.1be9
GigabitEthernet0/3 5254.0004.e87a 5254.0003.f510
Vlan10 5254.0014.800a 5254.0017.800a
Vlan10 (HSRP v1) 0000.0c07.ac0a (左と同じ)
Vlan20 5254.0014.8014 5254.0017.8014
Vlan20 (HSRP v1) 0000.0c07.ac14 (左と同じ)

HSRP の設定

HSRP は以下を設定しました。

IOSvL2-1

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interface Vlan10
 ip address 10.0.10.251 255.255.255.0
 standby 10 ip 10.0.10.254
 standby 10 timers 1 3
 standby 10 priority 110
 standby 10 preempt
 no shutdown
!
interface Vlan20
 ip address 10.0.20.251 255.255.255.0
 standby 20 ip 10.0.20.254
 standby 20 timers 1 3
 standby 20 priority 110
 standby 20 preempt
!
end

IOSvL2-2

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interface Vlan10
 ip address 10.0.10.252 255.255.255.0
 standby 10 ip 10.0.10.254
 standby 10 timers 1 3
 no shutdown
!
interface Vlan20
 ip address 10.0.20.252 255.255.255.0
 standby 20 ip 10.0.20.254
 standby 20 timers 1 3
!
end

状態確認

HSRP の状態は以下でした。

IOSvL2-1

show standby brief

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IOSvL2-1# show standby brief
                     P indicates configured to preempt.
                     |
Interface   Grp  Pri P State   Active          Standby         Virtual IP
Vl10        10   110 P Active  local           10.0.10.252     10.0.10.254
Vl20        20   110 P Active  local           10.0.20.252     10.0.20.254

show standby

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IOSvL2-1# show standby Vlan 10
Vlan10 - Group 10
  State is Active
    2 state changes, last state change 00:03:19
  Virtual IP address is 10.0.10.254
  Active virtual MAC address is 0000.0c07.ac0a (MAC In Use)
    Local virtual MAC address is 0000.0c07.ac0a (v1 default)
  Hello time 1 sec, hold time 3 sec
    Next hello sent in 0.624 secs
  Preemption enabled
  Active router is local
  Standby router is 10.0.10.252, priority 100 (expires in 3.120 sec)
  Priority 110 (configured 110)
  Group name is "hsrp-Vl10-10" (default)

show interfaces

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IOSvL2-1# show interfaces | include line protocol|Hardware
GigabitEthernet0/0 is up, line protocol is up (connected)
  Hardware is iGbE, address is 5254.0014.89fe (bia 5254.0014.89fe)
GigabitEthernet0/1 is up, line protocol is up (connected)
  Hardware is iGbE, address is 5254.0007.df55 (bia 5254.0007.df55)
GigabitEthernet0/2 is up, line protocol is up (connected)
  Hardware is iGbE, address is 5254.0017.e149 (bia 5254.0017.e149)
GigabitEthernet0/3 is up, line protocol is up (connected)
  Hardware is iGbE, address is 5254.0004.e87a (bia 5254.0004.e87a)
Vlan10 is up, line protocol is up
  Hardware is Ethernet SVI, address is 5254.0014.800a (bia 5254.0014.800a)
Vlan20 is up, line protocol is up
  Hardware is Ethernet SVI, address is 5254.0014.8014 (bia 5254.0014.8014)

IOSvL2-2

show standby brief

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IOSvL2-2# show standby brief
                     P indicates configured to preempt.
                     |
Interface   Grp  Pri P State   Active          Standby         Virtual IP
Vl10        10   100   Standby 10.0.10.251     local           10.0.10.254
Vl20        20   100   Standby 10.0.20.251     local           10.0.20.254

show standby

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IOSvL2-2# show standby Vlan 10
Vlan10 - Group 10
  State is Standby
    1 state change, last state change 00:03:07
  Virtual IP address is 10.0.10.254
  Active virtual MAC address is 0000.0c07.ac0a (MAC Not In Use)
    Local virtual MAC address is 0000.0c07.ac0a (v1 default)
  Hello time 1 sec, hold time 3 sec
    Next hello sent in 0.592 secs
  Preemption disabled
  Active router is 10.0.10.251, priority 110 (expires in 3.232 sec)
  Standby router is local
  Priority 100 (default 100)
  Group name is "hsrp-Vl10-10" (default)

show interfaces

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IOSvL2-2# show interfaces | include line protocol|Hardware
GigabitEthernet0/0 is up, line protocol is up (connected)
  Hardware is iGbE, address is 5254.0017.b51e (bia 5254.0017.b51e)
GigabitEthernet0/1 is up, line protocol is up (connected)
  Hardware is iGbE, address is 5254.0006.4a86 (bia 5254.0006.4a86)
GigabitEthernet0/2 is up, line protocol is up (connected)
  Hardware is iGbE, address is 5254.0013.1be9 (bia 5254.0013.1be9)
GigabitEthernet0/3 is up, line protocol is up (connected)
  Hardware is iGbE, address is 5254.0003.f510 (bia 5254.0003.f510)
Vlan10 is up, line protocol is up
  Hardware is Ethernet SVI, address is 5254.0017.800a (bia 5254.0017.800a)
Vlan20 is up, line protocol is up
  Hardware is Ethernet SVI, address is 5254.0017.8014 (bia 5254.0017.8014)

ARP テーブル

端末見立ての IOSv で ARP テーブルを確認すると以下でした。

IOSv-1

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IOSv-1# show ip arp
Protocol  Address          Age (min)  Hardware Addr   Type   Interface
Internet  10.0.10.111             -   5254.001f.7774  ARPA   GigabitEthernet0/0
Internet  10.0.10.254            14   0000.0c07.ac0a  ARPA   GigabitEthernet0/0

IOSv-2

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IOSv-2# show ip arp
Protocol  Address          Age (min)  Hardware Addr   Type   Interface
Internet  10.0.20.222             -   5254.0013.ec8b  ARPA   GigabitEthernet0/0
Internet  10.0.20.254            39   0000.0c07.ac14  ARPA   GigabitEthernet0/0

パケットキャプチャ

HSRP Hello パケットをキャプチャしたところ、Src / Dst MAC アドレスは以下になっていました。

IOSvL2-1 IOSvL2-2
HSRP State Active Standby
Src MAC Address 0000:0c07:ac0a 5254:0017:800a
Dst MAC Address 0100:5e00:0002 0100:5e00:0002

参考に VLAN 10 の MAC アドレスを再掲します。

Interface IOSvL2-1 IOSvL2-2
Vlan10 5254.0014.800a 5254.0017.800a
Vlan10 (HSRP v1) 0000.0c07.ac0a (左と同じ)

file

IOSvL2-1

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$ tshark -r hello-hsrp.pcap -V 'ip.src==10.0.10.251'
Frame 1: 62 bytes on wire (496 bits), 62 bytes captured (496 bits)
    Encapsulation type: Ethernet (1)
    Arrival Time: Dec 26, 2021 09:31:13.442041000 JST
    [Time shift for this packet: 0.000000000 seconds]
    Epoch Time: 1640478673.442041000 seconds
    [Time delta from previous captured frame: 0.000000000 seconds]
    [Time delta from previous displayed frame: 0.000000000 seconds]
    [Time since reference or first frame: 0.000000000 seconds]
    Frame Number: 1
    Frame Length: 62 bytes (496 bits)
    Capture Length: 62 bytes (496 bits)
    [Frame is marked: False]
    [Frame is ignored: False]
    [Protocols in frame: eth:ethertype:ip:udp:hsrp]
Ethernet II, Src: All-HSRP-routers_0a (00:00:0c:07:ac:0a), Dst: IPv4mcast_02 (01:00:5e:00:00:02)
    Destination: IPv4mcast_02 (01:00:5e:00:00:02)
        Address: IPv4mcast_02 (01:00:5e:00:00:02)
        .... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
        .... ...1 .... .... .... .... = IG bit: Group address (multicast/broadcast)
    Source: All-HSRP-routers_0a (00:00:0c:07:ac:0a)
        Address: All-HSRP-routers_0a (00:00:0c:07:ac:0a)
        .... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
        .... ...0 .... .... .... .... = IG bit: Individual address (unicast)
    Type: IPv4 (0x0800)
Internet Protocol Version 4, Src: 10.0.10.251, Dst: 224.0.0.2
    0100 .... = Version: 4
    .... 0101 = Header Length: 20 bytes (5)
    Differentiated Services Field: 0xc0 (DSCP: CS6, ECN: Not-ECT)
        1100 00.. = Differentiated Services Codepoint: Class Selector 6 (48)
        .... ..00 = Explicit Congestion Notification: Not ECN-Capable Transport (0)
    Total Length: 48
    Identification: 0x0000 (0)
    Flags: 0x00
        0... .... = Reserved bit: Not set
        .0.. .... = Don't fragment: Not set
        ..0. .... = More fragments: Not set
    ...0 0000 0000 0000 = Fragment Offset: 0
    Time to Live: 1
    Protocol: UDP (17)
    Header Checksum: 0xc400 [validation disabled]
    [Header checksum status: Unverified]
    Source Address: 10.0.10.251
    Destination Address: 224.0.0.2
User Datagram Protocol, Src Port: 1985, Dst Port: 1985
    Source Port: 1985
    Destination Port: 1985
    Length: 28
    Checksum: 0x82fc [unverified]
    [Checksum Status: Unverified]
    [Stream index: 0]
    [Timestamps]
        [Time since first frame: 0.000000000 seconds]
        [Time since previous frame: 0.000000000 seconds]
    UDP payload (20 bytes)
Cisco Hot Standby Router Protocol
    Version: 0
    Op Code: Hello (0)
    State: Active (16)
    Hellotime: Non-Default (1)
    Holdtime: Non-Default (3)
    Priority: 110
    Group: 10
    Reserved: 0
    Authentication Data: Default (cisco)
    Virtual IP Address: 10.0.10.254

IOSvL2-2

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$ tshark -r hello-hsrp.pcap -V 'ip.src==10.0.10.252'
Frame 2: 62 bytes on wire (496 bits), 62 bytes captured (496 bits)
    Encapsulation type: Ethernet (1)
    Arrival Time: Dec 26, 2021 09:31:14.157333000 JST
    [Time shift for this packet: 0.000000000 seconds]
    Epoch Time: 1640478674.157333000 seconds
    [Time delta from previous captured frame: 0.715292000 seconds]
    [Time delta from previous displayed frame: 0.000000000 seconds]
    [Time since reference or first frame: 0.715292000 seconds]
    Frame Number: 2
    Frame Length: 62 bytes (496 bits)
    Capture Length: 62 bytes (496 bits)
    [Frame is marked: False]
    [Frame is ignored: False]
    [Protocols in frame: eth:ethertype:ip:udp:hsrp]
Ethernet II, Src: RealtekU_17:80:0a (52:54:00:17:80:0a), Dst: IPv4mcast_02 (01:00:5e:00:00:02)
    Destination: IPv4mcast_02 (01:00:5e:00:00:02)
        Address: IPv4mcast_02 (01:00:5e:00:00:02)
        .... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
        .... ...1 .... .... .... .... = IG bit: Group address (multicast/broadcast)
    Source: RealtekU_17:80:0a (52:54:00:17:80:0a)
        Address: RealtekU_17:80:0a (52:54:00:17:80:0a)
        .... ..1. .... .... .... .... = LG bit: Locally administered address (this is NOT the factory default)
        .... ...0 .... .... .... .... = IG bit: Individual address (unicast)
    Type: IPv4 (0x0800)
Internet Protocol Version 4, Src: 10.0.10.252, Dst: 224.0.0.2
    0100 .... = Version: 4
    .... 0101 = Header Length: 20 bytes (5)
    Differentiated Services Field: 0xc0 (DSCP: CS6, ECN: Not-ECT)
        1100 00.. = Differentiated Services Codepoint: Class Selector 6 (48)
        .... ..00 = Explicit Congestion Notification: Not ECN-Capable Transport (0)
    Total Length: 48
    Identification: 0x0000 (0)
    Flags: 0x00
        0... .... = Reserved bit: Not set
        .0.. .... = Don't fragment: Not set
        ..0. .... = More fragments: Not set
    ...0 0000 0000 0000 = Fragment Offset: 0
    Time to Live: 1
    Protocol: UDP (17)
    Header Checksum: 0xc3ff [validation disabled]
    [Header checksum status: Unverified]
    Source Address: 10.0.10.252
    Destination Address: 224.0.0.2
User Datagram Protocol, Src Port: 1985, Dst Port: 1985
    Source Port: 1985
    Destination Port: 1985
    Length: 28
    Checksum: 0x8b05 [unverified]
    [Checksum Status: Unverified]
    [Stream index: 1]
    [Timestamps]
        [Time since first frame: 0.000000000 seconds]
        [Time since previous frame: 0.000000000 seconds]
    UDP payload (20 bytes)
Cisco Hot Standby Router Protocol
    Version: 0
    Op Code: Hello (0)
    State: Standby (8)
    Hellotime: Non-Default (1)
    Holdtime: Non-Default (3)
    Priority: 100
    Group: 10
    Reserved: 0
    Authentication Data: Default (cisco)
    Virtual IP Address: 10.0.10.254