Application Support for Stateful SRP Switchover

DS1

✓

–

–

HDLC

✓

–

–

SONET/SDH VT

✓

–

–

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).

Bridged Ethernet

✓

–

–

Ethernet (with and without VLANs)

✓

–

–

PPP

✓

–

–

Transparent bridging

✓

–

–

Access Routes

✓

–

–

BGP

✓

–

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

IP

✓

–

–

IPv6 neighbor discovery

✓

–

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

IPSec Tunnels

✓

–

Completed IKE phase 1 and phase 2 negotiations supported only.

IS-ISv6

✓

–

Supported only when the graceful restart extension is enabled.

OSPFv3

✓

–

Supported only when the graceful restart extension is enabled.

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.

DVMRP

✓

–

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

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.

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.

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.

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.

MPLS over IPv6 supports HA. This functionality enables BGP to support graceful restart for IPv6 labeled addresses.

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.

Local cross-connects between layer 2 interfaces using MPLS

✓

–

–

Policies

✓

–

–

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 Proxy Client

✓

–

When the standby SRP module takes over as the primary after a stateful SRP switchover operation, it continues to handle DHCP lease renewal requests from existing clients based on their states and processes state transitions without any disruption. For more information, see "Preservation of DHCP Proxy Client Bindings During Stateful SRP Switchover"

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.

DHCPv6 Local Server

✓

–

DHCPv6 now supports stateful SRP switchover (high availability).

After SRP warm switchover, the router restores the client bindings from the mirrored DHCPv6 information as it does for other applications that support stateful SRP switchover.

L2TP Dialout

–

✓

–

IPv6 Local Address Pools

✓

–

When the IPv6 local pools are configured, you can perform an HA switchover without cold booting the router because the configuration is now HA safe. The prefix assigned to the subscriber, before and after the warm restart, remains the same. The In Use prefix count also remains the same before and after the warm restart.

RADIUS Dynamic-Request Server

✓

–

Static recovery support only.

RADIUS Relay Server

✓

–

–

Service Manager

✓

–

–

TACACS+

✓

–

Static recovery support only.

DNS

✓

–

—

J-Flow (IP flow statistics)

✓

–

–

Network Address Translation

✓

–

–

Resource Threshold Monitor

✓

–

–

Route Policy

✓

–

Static recovery support only.

Tunnels (GRE and DVMRP)

✓

–

–