このドキュメントでは NAT Box to Box High Availabitliy (以下、NAT B2B HA) の基本的な動作概要と確認方法を説明します。
1. NAT Box to Box 構成確認
本ドキュメントで使用する NAT B2B HA 基本構成を下記に示します。

NAT B2B HA が正しく構成されていること以下のコマンドにより確認できます。
R1#show redundancy application group 1
Group ID:1
Group Name:RG1
Administrative State: No Shutdown
Aggregate operational state : Up
My Role: ACTIVE
Peer Role: STANDBY
Peer Presence: Yes
Peer Comm: Yes
Peer Progression Started: Yes
RF Domain: btob-one
RF state: ACTIVE
Peer RF state: STANDBY HOT
R2#show redundancy application group 1
Group ID:1
Group Name:RG1
Administrative State: No Shutdown
Aggregate operational state : Up
My Role: STANDBY
Peer Role: ACTIVE
Peer Presence: Yes
Peer Comm: Yes
Peer Progression Started: Yes
RF Domain: btob-one
RF state: STANDBY HOT
Peer RF state: ACTIVE
R1#show ip nat redundancy 1
RG ID: 1 RG Name: RG1
Current State: IPNAT_HA_RG_ST_ACT_BULK_DONE
Previous State: IPNAT_HA_RG_ST_ACT_BULK_START
Recent Events: Curr: IPNAT_HA_RG_EVT_RF_ACT_STBY_HOT
Prev: IPNAT_HA_RG_EVT_ACT_BULK_SYNC_DONE
Statistics :
Static Mappings: 2, Dynamic Mappings: 0
Sync-ed Entries :
NAT Entries: 0, Door Entries: 0
Mapping ID Mismatches: 0
Forwarded Packets: 33623, Dropped Packets : 0
Redirected Packets: 0
R1#show ip nat translations redundancy 1
Pro Inside global Inside local Outside local Outside global
--- 172.16.1.50 192.168.1.100 --- ---
--- 10.255.255.50 192.168.1.200 --- ---
※ 現時点の実装では 複数の RG を使うことは推奨されませんので、 "show ip nat translations" のみでも構いません。
2. LAN to LAN の動作確認
本項では下記図のような状況における動作確認方法を示します。

Client A より LAN Server 宛てに telnet 接続を実施します。
Client A#telnet 172.16.1.100
Trying 172.16.1.100 ... Open
R1 にて該当通信のNATエントリが生成されます。
R1#show ip nat translation | i tcp
Pro Inside global Inside local Outside local Outside global
tcp 172.16.1.50:13596 192.168.1.100:13596 172.16.1.100:23 172.16.1.100:23
R1 にてNAT変換が実行されたことがわかります。
R1#show ip nat statistics | i packets
CEF Translated packets: 243, CEF Punted packets: 1
R2 にも同時に、同じNATエントリが生成されます。
R2#show ip nat translation | i tcp
Pro Inside global Inside local Outside local Outside global
tcp 172.16.1.50:13596 192.168.1.100:13596 172.16.1.100:23 172.16.1.100:23
R2 は Standby 状態ですので、通信は経由されません。
R2#show ip nat statistics | i packets
CEF Translated packets: 0, CEF Punted packets: 0
コンフィグは以下の通りです。
R1#
redundancy
application redundancy
group 1
name RG1
preempt
priority 105
control Ethernet0/1 protocol 1
data Ethernet0/1
interface Ethernet0/0
description ## To Client ##
ip address 192.168.1.1 255.255.255.0
ip nat inside
ip virtual-reassembly in
redundancy rii 100
redundancy group 1 ip 192.168.1.254 exclusive decrement 100
interface Ethernet0/1
description ## Control-Link ##
ip address 10.0.0.1 255.255.255.0
interface Ethernet1/0
ip address 172.16.1.1 255.255.255.0
ip nat outside
ip virtual-reassembly in
redundancy rii 101
redundancy group 1 ip 172.16.1.254 exclusive decrement 100
ip nat inside source static 192.168.1.100 172.16.1.50 redundancy 1 mapping-id 120
R2#
redundancy
application redundancy
group 1
name RG1
preempt
control Ethernet0/1 protocol 1
data Ethernet0/1
interface Ethernet0/0
description ## To Client ##
ip address 192.168.1.2 255.255.255.0
ip nat inside
ip virtual-reassembly in
redundancy rii 100
redundancy group 1 ip 192.168.1.254 exclusive decrement 100
interface Ethernet0/1
description ## Control-Link ##
ip address 10.0.0.2 255.255.255.0
interface Ethernet1/0
ip address 172.16.1.2 255.255.255.0
ip nat outside
ip virtual-reassembly in
redundancy rii 101
redundancy group 1 ip 172.16.1.254 exclusive decrement 100
ip nat inside source static 192.168.1.100 172.16.1.50 redundancy 1 mapping-id 120
下記ドキュメントも参考にしてください。