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Application Support

Applications are either supported or unsupported by high availability.

Table 46 indicates which applications support or do not support stateful SRP switchover.

Table 46: Application Support for Stateful SRP Switchover

Application

Supported

Unsupported

Notes

Physical Layer Protocols

DS1

DS3

HDLC

SONET/SDH

SONET/SDH VT

Link-Layer Protocols

ATM

Static and dynamic interfaces, with the exception of ATM subscribers, are supported.

In this case, ATM subscribers refers to a technology on the E-series router where the ATM layer does authentication (that is, not PPP or IP subscriber manager).

ATM 1483 bulk configuration of dynamic interfaces

Bridged Ethernet

Cisco HDLC

Ethernet (with and without VLANs)

Frame Relay

PPP

PPPoE

Transparent bridging

Unicast Routing

Access Routes

BGP

Supported for IPv4 only when the graceful restart extension is enabled. Does not support graceful restart for IPv6 address families.

FTP

Static recovery support only.

IP

IPv6

IPv6 neighbor discovery

IPv6 neighbor discovery characteristics are replayed during switchover. Line modules do not flush neighbor discovery information during the switchover.

IPSec Transport

IPSec Tunnels

Completed IKE phase 1 and phase 2 negotiations supported only.

IS-IS

Supported only when the graceful restart extension is enabled.

IS-ISv6

Supported only when the graceful restart extension is enabled.

OSPFv2

 

Supported only when the graceful restart extension is enabled.

OSPFv3

Supported only when the graceful restart extension is enabled.

RIP

Static recovery support only.

Static Routes (IP and IPv6)

After all high-priority interfaces have been replayed from NVS and mirrored storage, static routes are replayed from NVS, followed by replay of low-priority interfaces from NVS and mirrored storage. This behavior enables static routes that are dependent on high-priority interfaces to be resolved quickly and installed in the IP routing table.

Telnet

Static recovery support only.

IPv4 Multicast Routing

Multicast Routing

Static recovery support only. During switchover, the system mirrors the multicast queue so that IP can use the same queue without needing to recreate a different connection.

DVMRP

Static recovery support only. DVMRP gives the restart complete indication to the IP routing table after getting a peer update (60-second time-out).

IGMP

IC IGMP deletes its interface and membership state on SRP failover (controller down). As part of SRP warm start, IGMP interfaces are reconfigured from NVS and dynamic IGMP interfaces are reconfigured from mirrored storage. IGMP hosts are queried as IP interfaces come back up, the join state is re-established, and SC IGMP state is created.

After the maximum query response time (across all interfaces) expires to allow hosts to re-establish join state, IGMP notifies MGTM that graceful restart is complete.

MGTM

On SRP failover, old mroutes are retained on the line module to preserve multicast forwarding; cache-misses to the SRP are disabled. When MGTM warm starts on the SRP, it reads the NVS configuration and enables multicast routing. When IGMP, DVMRP, and PIM have completed graceful restart and the IP route table multicast-view has completed graceful restart, old mroutes are deleted from the line module and cache-misses to the SRP are enabled. This triggers re-creation of mroutes and establishes the current multicast forwarding state.

Although cache-misses to the SRP module are disabled, forwarding is preserved for old multicast joins to downstream routers and hosts. However, forwarding for new multicast joins requested by downstream routers and hosts after SRP module switchover is not provided until cache-misses are re-enabled.

PIM

Static recovery support only. For warm start, PIM interfaces are reconfigured from NVS. A Hello message with a new Generation ID is issued as IP interfaces come up. A neighbor that receives this Hello determines that the upstream neighbor has lost state and needs to be refreshed. A VR-global configurable graceful restart timer is required for PIM to time out the re-establishment of the join state for sparse-mode interfaces. After this timer expires, PIM notifies MGTM that graceful restart is complete.

IPv6 Multicast Routing 

Multicast Routing

Static recovery support only. During switchover, the system mirrors the multicast queue so that IPv6 can use the same queue without needing to recreate a different connection.

MGTM

On SRP failover, old mroutes are retained on the line module to preserve multicast forwarding; cache-misses to the SRP are disabled. When MGTM warm starts on the SRP, it reads the NVS configuration and enables multicast routing. When MLD and PIM have completed graceful restart and the IPv6 route table multicast-view has completed graceful restart, old mroutes are deleted from the line module and cache-misses to the SRP are enabled. This triggers re-creation of mroutes and establishes the current multicast forwarding state.

Although cache-misses to the SRP module are disabled, forwarding is preserved for old multicast joins to downstream routers and hosts. However, forwarding for new multicast joins requested by downstream routers and hosts after SRP module switchover is not provided until cache-misses are re-enabled.

MLD

IC MLD deletes its interface and membership state on SRP failover (controller down). As part of SRP warm start, MLD interfaces are reconfigured from NVS and dynamic IMLD interfaces are reconfigured from mirrored storage. MLD hosts are queried as IPv6 interfaces come back, the join state is re-established, and SC MLD state is created. After the maximum query response time (across all interfaces) expires to allow hosts to re-establish join state, MLD notifies MGTMv6 that graceful restart is complete.

PIM

Static recovery support only. For warm start, PIM interfaces are reconfigured from NVS and a Hello message with a new Generation ID is issued as IPv6 interfaces come up. A neighbor that receives this Hello determines that the upstream neighbor has lost state and needs to be refreshed. A VR-global configurable graceful restart timer is required for PIM to time out the re-establishment of the join state for sparse-mode interfaces. After this timer expires, PIM notifies MGTM that graceful restart is complete.

Multiprotocol Label Switching

MPLS

MPLS is HA-unsafe during a graceful restart. It is HA-unsafe until all the configured MPLS signaling protocols have completed their graceful restart procedures and any stale forwarding elements have been flushed from the line modules.

If you force an SRP switchover while MPLS is HA-unsafe, the SRP module switches but the SRP module and the line modules undergo a cold restart.

If the primary SRP module resets while MPLS is HA-unsafe, the router undergoes a cold restart.

In addition, MPLS over IPv6 does not support HA. If it is configured, no warning or error is displayed during a warm start. MPLS is subsequently configured from NVS as it would be after a cold reboot.

BGP signaling

 

LDP signaling

To provide uninterrupted service during an SRP switchover in a scaled configuration, such as one with 32,000 Martini circuits, set the LDP graceful restart reconnect time to the maximum 300 seconds and set the LDP graceful restart recovery timer to the maximum 600 seconds. This requirement is true for all SRP switchovers, including those in the context of a unified in-service software upgrade.

LDP signaling does not support HA for IPv6.

RSVP signaling

 

Local cross-connects between layer 2 interfaces using MPLS

Policies and QoS

Policies

QoS

Static recovery support only.

Remote Access

AAA

DHCP External Server and Packet Trigger

Following a switchover, the DHCP lease (that is, time remaining) is recalculated based on when the lease started. When the release timer for a client expires, the client is deleted and the access route is removed, along with the dynamic subscriber interface if it was created. If the client requests a new lease, DHCP external server resynchronizes with the new lease time.

DHCP Packet Capture

DHCP Proxy Client

DHCP Relay Proxy

 

DHCP Relay Server

Before HA support, clients identified by the DHCP relay server were maintained on a switchover (their state was stored to NVS); DHCP relay server always had some level of HA support.

Currently, following a switchover, the DHCP lease (that is, time remaining) is reset. When the release timer for a client expires, the client requests a new lease. The E-series router DHCP relay server then synchronizes with the new state.

DHCPv4 Local Server

DHCPv6 Local Server

 

L2TP

L2TP Dialout

Local Address Pools

The internal local address server state supports only static recovery. However, the AAA application reallocates active addresses on a switchover. The resulting effect is the local address server having full HA support.

RADIUS Client

Similar to local address server, AAA recovers disrupted RADIUS communication on a switchover. The resulting effect is the RADIUS client having full HA support.

RADIUS Dynamic-Request Server

Static recovery support only.

RADIUS Initiated Disconnect

 

RADIUS Relay Server

RADIUS Route-Download Server

SRC Client

TACACS+

Static recovery support only.

Miscellaneous

DNS

 

DNSv6

If DNSv6 is configured, no warning or error is displayed during a warm start. DNSv6 is subsequently configured from NVS as it would be after a cold reboot.

J-Flow (IP flow statistics)

Line Module Redundancy

Network Address Translation

NTP

Resource Threshold Monitor

Response Time Reporter

Route Policy

Static recovery support only.

Subscriber Interfaces

IPv4 only. Subscriber interfaces are not applicable to IPv6

Tunnels (GRE and DVMRP)

VRRP

Static recovery support only.

Caution: When IP tunnels are configured on an HA-enabled router and the Service Module (SM) carrying these tunnels is reloaded, HA transitions to the pending state. HA remains in the pending state for 5 minutes after the successful reloading of the SM. This amount of time allows for IP tunnel relocation and for the tunnels to become operational again on the SM. If an SRP switchover occurs while HA is in the pending state, the router performs a cold restart.


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