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The Firewall Stateful Interchassis Redundancy feature enables you to configure pairs of routers to act as backup for each
other. This feature can be configured to determine the active router based on a number of failover conditions. When a failover
occurs, the standby router seamlessly takes over and starts performing traffic forwarding services and maintaining a dynamic
routing table.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest caveats and feature information,
see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module,
and to see a list of the releases in which each feature is supported, see the feature information table.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature
Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Prerequisites for Firewall Stateful Interchassis Redundancy
The interfaces attached to the firewall must have the same redundant interface identifier (RII).
The active device and the standby device must have the same Cisco IOS XE Zone-Based Firewall configuration.
The active device and the standby device must run on an identical version of the Cisco IOS XE software. The active device
and the standby device must be connected through a switch.
Embedded Service Processor (ESP) must match on both active and standby devices.
Restrictions for Firewall
Stateful Interchassis Redundancy
LAN and MESH
scenarios are not supported.
Cisco ASR 1006 and Cisco ASR
1013 platforms with dual Embedded Services Processors (ESPs) or dual Route
Processors (RPs) in the chassis are not supported, because coexistence of
interbox high availability (HA) and intrabox HA is not supported.
Cisco ASR 1006
and Cisco ASR 1013 platforms with single ESP and single RP in the chassis
supports interchassis redundancy.
If the dual IOS
daemon (IOSd) is configured, the device will not support the firewall Stateful
Interchassis Redundancy configuration.
Information About Firewall Stateful Interchassis Redundancy
How Firewall Stateful Inter-Chassis Redundancy Works
You can configure pairs of routers to act as hot standbys for each other. This redundancy is configured on an interface basis.
Pairs of redundant interfaces are known as redundancy groups. The figure below depicts the active-standby device scenario.
It shows how the redundancy group is configured for a pair of routers that has one outgoing interface. The
Redundancy Group Configuration--Two Outgoing Interfaces figure depicts the active-active device scenario shows how two redundancy groups are configured for a pair of routers that
have two outgoing interfaces.
Note that in both cases, the redundant routers are joined by a configurable control link and a data synchronization link.
The control link is used to communicate the status of the routers. The data synchronization link is used to transfer stateful
information from Network Address Translation (NAT) and the firewall and to synchronize the stateful database for these applications.
Also, in both cases, the pairs of redundant interfaces are configured with the same unique ID number known as the RII.
The status of redundancy group members is determined through the use of hello messages sent over the control link. If either
of the routers does not respond to a hello message within a configurable amount of time, it is considered that a failure has
occurred, and a switchover is initiated. To detect a failure in milliseconds, the control links run the failover protocol
integrated with the Bidirectional Forwarding Detection (BFD) protocol. You can configure the following parameters for the
hello messages:
Active timer
Standby timer
Hellotime--The interval at which hello messages are sent
Holdtime--The amount of time before the active or the standby router is declared to be down
The hellotime defaults to 3 seconds to align with Hot Standby Router Protocol (HSRP), and the holdtime defaults to 10 seconds.
You can also configure these timers in milliseconds by using the
timers hellotime msec command.
To determine which pairs of interfaces are affected by the switchover, you must configure a unique ID number for each pair
of redundant interfaces. This ID number is known as the RII associated with the interface.
A switchover to the standby router can also occur under other circumstances. Another factor that can cause a switchover is
a priority setting that is configurable for each router. The router with the highest priority value will be the active router.
If a fault occurs on either the active or the standby router, the priority of the router is decremented by a configurable
amount known as the weight. If the priority of the active router falls below the priority of the standby router, a switchover
occurs and the standby router becomes the active router. This default behavior can be overridden by disabling the preemption
attribute for the redundancy group. You can also configure each interface to decrease the priority when the L1 state of the
interface goes down. This amount overrides the default amount configured for the redundancy group.
Each failure event that causes a modification of a redundancy group’s priority generates a syslog entry that contains a time
stamp, the redundancy group that was affected, previous priority, new priority, and a description of the failure event cause.
Another situation that will cause a switchover to occur is when the priority of a router or interface falls below a configurable
threshold level.
In general, a switchover to the standby router occurs under the following circumstances:
Power loss or reload occurs on the active router (this includes crashes).
The run-time priority of the active router goes down below that of the standby router.
The run-time priority of the active router goes down below the configured threshold value.
The redundancy group on the active router is reloaded manually using the
redundancy application reload group rg-number command.
Two consecutive hello messages missed on any monitored interface forces the interface into testing mode. When this occurs,
both units first verify the link status on the interface and then execute the following tests:
Network activity test
ARP test
Broadcast ping test
In the Firewall Stateful Inter-Chassis Redundancy feature, the redundancy group traffic is routed through the virtual IP address
that is associated with the ingress interface of the redundancy group. The traffic sent to the virtual IP address is received
by the router that has the redundancy group in the active state. During a redundancy group failover, the traffic to the virtual
IP address is automatically routed to the newly active redundancy group.
The firewall drops the traffic that arrives on the standby redundancy group in case the redundancy group traffic is routed
through the physical IP address of a standby router and the traffic reaches the standby redundancy group. However, when the
traffic arrives on the active redundancy group, the established TCP or UDP sessions are synchronized to the standby redundancy
group.
Exclusive Virtual IP Addresses and Exclusive Virtual MAC Addresses
Virtual IP (VIP) addresses and virtual MAC (VMAC) addresses are used by security applications to control interfaces that
receive traffic. An interface is paired with another interface, and these interfaces are associated with the same redundancy
group (RG). The interface that is associated with an active RG exclusively owns the VIP and VMAC. The Address Resolution Protocol
(ARP) process on the active device sends ARP replies for any ARP request for the VIP, and the Ethernet controller for the
interface is programmed to receive packets destined for the VMAC. When an RG failover occurs, the ownership of the VIP and
VMAC changes. The interface that is associated with the newly active RG sends a gratuitous ARP and programs the interface’s
Ethernet controller to accept packets destined for the VMAC.
IPv6 Support
You can assign each redundancy group (RG) on a traffic interface for both IPv4 and IPv6 virtual IP (VIP) addresses under the
same redundancy interface identifier (RII). Each RG uses a unique virtual MAC (VMAC) address per RII. For an RG, the IPv6
link-local VIP and global VIP coexist on an interface.
You can configure an IPv4 VIP, a link-local IPv6 VIP, and/or a global IPv6 VIP for each RG on a traffic interface. IPv6 link-local
VIP is mainly used when configuring static or default routes, whereas IPv6 global VIP is widely used in both LAN and WAN topologies.
You must configure a physical IP address before configuring an IPv4 VIP.
Supported Topologies
The LAN-LAN topology is supported in the Firewall Stateful Inter-Chassis Redundancy architecture:
LAN-LAN
The figure below shows the LAN-LAN topology. When a dedicated appliance-based firewall solution is used, traffic is often
directed to the correct firewall by configuring static routing in the upstream or downstream routers to an appropriate virtual
IP address. In addition, the Aggregation Services Routers (ASRs) will participate in dynamic routing with upstream or downstream
routers. The dynamic routing configuration supported on LAN facing interfaces must not introduce a dependency on routing protocol
convergence; otherwise, fast failover requirements will not be met.
For more information about the LAN-LAN configuration, see the section, Example Configuring LAN-LAN.
VRF-Aware
Interchassis Redundancy in Zone-Based Firewalls
In Cisco IOS XE
Release 3.14S, zone-based firewalls support VRF-aware interchassis redundancy.
The VPN routing and forwarding (VRF) name at the active and standby devices
must the same. The same VRF configuration must be available on both active and
standby devices.
The VRF-Aware Interchassis Redundancy in Zone-Based Firewalls feature
uses a VRF mapping mechanism that sends the VRF hash key along with box-to-box
high availability session sync messages across active and standby devices.
How to Configure Firewall Stateful Interchassis Redundancy
Configuring a Redundancy Application Group
SUMMARY STEPS
enable
configure terminal
redundancy
application redundancy
group id
name group-name
shutdown
priority value [failover threshold value]
preempt
track object-number{decrement value |
shutdown }
end
DETAILED STEPS
Command or Action
Purpose
Step 1
enable
Example:
Device> enable
Enables privileged EXEC mode.
Enter your password if prompted.
Step 2
configure terminal
Example:
Device# configure terminal
Enters global configuration mode.
Step 3
redundancy
Example:
Device(config)# redundancy
Enters redundancy configuration mode.
Step 4
application redundancy
Example:
Device(config-red)# application redundancy
Enters redundancy application configuration mode.
Step 5
group id
Example:
Device(config-red-app)# group 1
Enters redundancy application group configuration mode.
Step 6
name group-name
Example:
Device(config-red-app-grp)# name group1
(Optional) Specifies an optional alias for the protocol instance.
Step 7
shutdown
Example:
Device(config-red-app-grp)# shutdown
(Optional) Shuts down a redundancy group manually.
Example: Configuring a
Virtual IP Address and a Redundant Interface Identifier
The following
example shows how to configure the redundancy group virtual IP address for
Gigabit Ethernet interface 0/1/1:
Device# configure terminal
Device(config)# interface GigabitEthernet 0/1/1
Device(conf-if)# redundancy rii 600
Device(config-if)# redundancy group 2 ip 10.2.3.4 exclusive decrement 200
Device(config-if)# end
Example: Configuring a Control Interface and a Data Interface
Device# configure terminal
Device(config-red)# application redundancy
Device(config-red-app-grp)# group 1
Device(config-red-app-grp)# data GigabitEthernet 0/0/0
Device(config-red-app-grp)# control GigabitEthernet 0/0/2 protocol 1
Device(config-red-app-grp)# timers delay 100 reload 400
Device(config-red-app-grp)# end
Example: Configuring a
LAN-LAN Topology
The following is a
sample LAN-LAN configuration that shows how a pair of routers that have two
outgoing interfaces are configured for stateful redundancy. In this example,
GigabitEthernet 0/1/1 is the ingress interface and GigabitEthernet 0/2/1 is the
egress interface. Both interfaces are assigned to zones and a classmap is
defined to describe the traffic between zones. Interfaces are also configured
for redundancy. The “inspect” action invokes the application-level gateway
(ALG) to open a pinhole to allow traffic on other ports. A pinhole is a port
that is opened through an ALG to allow a particular application to gain
controlled access to a protected network.
The following is the
configuration on Device 1, the active device.
! Configures redundancy, control and data interfaces
redundancy
mode none
application redundancy
group 2
preempt
priority 200 failover threshold 100
control GigabitEthernet 0/0/4 protocol 2
data GigabitEthernet 0/0/3
!
protocol 2
timers hellotime ms 250 holdtime ms 750
!
! Configures a VRF
ip vrf vrf1
!
! Configures parameter maps to add parameters that control the behavior of actions and match criteria.
parameter-map type inspect pmap-udp
redundancy
redundancy delay 10
!
parameter-map type inspect pmap-tcp
redundancy
redundancy delay 10
!
! Defines class-maps to describes traffic between zones
class-map type inspect match-any cmap-udp
match protocol udp
!
class-map type inspect match-any cmap-ftp-tcp
match protocol ftp
match protocol tcp
!
! Associates class-maps with policy-maps to define actions to be applied
policy-map type inspect p1
class type inspect cmap-udp
inspect pmap-udp
!
class type inspect cmap-ftp-tcp
inspect pmap-tcp
!
! Identifies and defines network zones
zone security z-int
!
zone security z-hi
!
! Sets zone pairs for any policy other than deny all and assign policy-maps to zone-pairs by defining a service-policy
zone-pair security hi2int source z-hi destination z-int
service-policy type inspect p1
!
! Assigns interfaces to zones
interface GigabitEthernet 0/0/1
ip vrf forwarding vrf1
ip address 10.1.1.3 255.255.0.0
ip virtual-reassembly
zone-member security z-hi
negotiation auto
redundancy rii 20
redundancy group 2 ip 10.1.1.10 exclusive decrement 50
!
interface GigabitEthernet 0/0/2
ip vrf forwarding vrf1
ip address 192.0.2.2 255.255.255.240
ip virtual-reassembly
zone-member security z-int
negotiation auto
redundancy rii 21
redundancy group 2 ip 192.0.2.12 exclusive decrement 50
!
interface GigabitEthernet 0/0/4
ip address 198.51.100.17 255.255.255.240
!
interface GigabitEthernet 0/0/4
ip address 203.0.113.49 255.255.255.240
!
ip route vrf vrf1 192.0.2.0 255.255.255.240 GigabitEthernet0/0/2 10.1.1.4
ip route vrf vrf1 10.1.0.0 255.255.0.0 GigabitEthernet0/0/1 10.1.0.4
!
The following is the
configuration on Device 2, the standby device:
! Configures redundancy, control and data interfaces
redundancy
mode none
application redundancy
group 2
preempt
priority 200 failover threshold 100
control GigabitEthernet 0/0/4 protocol 2
data GigabitEthernet 0/0/3
!
protocol 2
timers hellotime ms 250 holdtime ms 750
!
! Configures a VRF
ip vrf vrf1
!
! Configures parameter maps to add parameters that control the behavior of actions and match criteria.
parameter-map type inspect pmap-udp
redundancy
redundancy delay 10
!
parameter-map type inspect pmap-tcp
redundancy
redundancy delay 10
!
! Defines class-maps to describes traffic between zones
class-map type inspect match-any cmap-udp
match protocol udp
!
class-map type inspect match-any cmap-ftp-tcp
match protocol ftp
match protocol tcp
!
! Associates class-maps with policy-maps to define actions to be applied
policy-map type inspect p1
class type inspect cmap-udp
inspect pmap-udp
!
class type inspect cmap-ftp-tcp
inspect pmap-tcp
!
! Identifies and defines network zones
zone security z-int
!
zone security z-hi
!
! Sets zone pairs for any policy other than deny all and assign policy-maps to zone-pairs by defining a service-policy
zone-pair security hi2int source z-hi destination z-int
service-policy type inspect p1
!
! Assigns interfaces to zones
interface GigabitEthernet 0/0/1
ip vrf forwarding vrf1
ip address 10.1.1.6 255.255.0.0
ip virtual-reassembly
zone-member security z-hi
negotiation auto
redundancy rii 20
redundancy group 2 ip 10.1.1.12 exclusive decrement 50
!
interface GigabitEthernet 0/0/2
ip vrf forwarding vrf1
ip address 192.0.2.5 255.255.255.240
ip virtual-reassembly
zone-member security z-int
negotiation auto
redundancy rii 21
redundancy group 2 ip 192.0.2.10 exclusive decrement 50
!
interface GigabitEthernet 0/0/4
ip address 198.51.100.21 255.255.255.240
!
interface GigabitEthernet 0/0/4
ip address 203.0.113.53 255.255.255.240
!
ip route vrf vrf1 192.0.2.0 255.255.255.240 GigabitEthernet0/0/2 10.1.1.4
ip route vrf vrf1 10.1.0.0 255.255.0.0 GigabitEthernet0/0/1 10.1.0.4
!
Additional References for Firewall Stateful Interchassis Redundancy
The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use
these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products
and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.
Feature Information for
Firewall Stateful Interchassis Redundancy
The following table provides release information about the feature or features described in this module. This table lists
only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise,
subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco
Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Table 1. Feature Information for
Firewall Stateful Interchassis Redundancy
Feature
Name
Releases
Feature
Information
Firewall
Stateful Interchassis Redundancy
Cisco IOS
XE Release 3.1(S)
The
Firewall Stateful Interchassis Redundancy feature enables you to configure
pairs of devices to act a backups for each other.
The
following commands were introduced or modified:
application redundancy ,
authentication ,control ,
data ,
debug redundancy application group config ,
debug redundancy application group faults ,
debug redundancy application group media ,
debug redundancy application group protocol ,
debug redundancy application group rii ,
debug redundancy application group transport ,
debug redundancy application group vp ,
group ,
name ,
preempt ,
priority ,
protocol ,
redundancy rii ,
redundancy group ,
track ,
timers delay ,
timers hellotime ,
show redundancy application group ,
show redundancy application transport ,
show redundancy application control-interface ,
show redundancy application faults ,
show redundancy application protocol ,
show redundancy application if-mgr ,
show redundancy application data-interface .
VRF-Aware Stateful Interchassis Redundancy in Zone-Based
Firewalls
Cisco IOS XE Release 3.14S
In Cisco IOS XE Release 3.14S, zone-based firewalls support
VRF-aware interchassis redundancy. The VPN routing and forwarding (VRF) name at
the active and standby devices must the same. The same VRF configuration must
be available on both active and standby devices.