# Application Support for Unified ISSU

When an application supports unified ISSU, you can configure the application on the router and proceed with the unified in-service software upgrade with no adverse impact to the upgrade.

Applications that do not support unified ISSU cannot maintain state and configuration with minimal traffic loss across the upgrade. When you attempt the unified in-service software upgrade on a router that is configured with an ISSU-challenged application, the unified in-service software upgrade is halted and cannot proceed unless you remove the configuration. An application that does not support high availability cannot support unified ISSU.

Table 20 indicates which applications support or do not support a unified in-service software upgrade, as well as limitations on their behavior.

Table 20: Application Support for Unified In-Service Software Upgrades

Application | Supported | Unsupported | Notes
--- | --- | --- | ---
Physical Layer Protocols |  |  |
DS1 (E120 and E320) | – | – | –
DS1 (ERX1440) | – | – | –
DS3 | ✓ | – | –
HDLC | ✓ | – | –
SONET/SDH | ✓ | – | Unified ISSU support is provided only for non-channelized APS IOAs. Also, unified ISSU can proceed only if you have not configured APS on the OCx/STMx ATM or OCx/STMx POS line modules. If you have configured APS, a warning message is displayed and the router cannot proceed with the unified ISSU. The unified ISSU process for channelized line modules remains unchanged. E120 and E320 routers do not support APS.
SONET/SDH VT | – | ✓ | –
Link-Layer Protocols |  |  |
ARP | ✓ | – | ARP entries in the ARP cache do not time out because no ARP aging occurs during unified ISSU. When the unified ISSU is completed, the ARP cache contains the same entries as it had before the unified ISSU began.
ATM | ✓ | – | –
ATM 1483 bulk configuration of dynamic interfaces | ✓ | – | –
ATM bulk configuration of static interfaces | ✓ | – | –
Bridged Ethernet | ✓ | – | –
Cisco HDLC | ✓ | – | –
Ethernet (with and without VLANs) | ✓ | – | –
Frame Relay | – | – | –
PPP | ✓ | – | –
PPPoE | ✓ | – | –
Transparent bridging | ✓ | – | –
Unicast Routing |  |  |
Access Routes | ✓ | – | –
BGP | ✓ | – | –
FTP | ✓ | – | Although unified ISSU supports FTP in active state, no file transfer operation can be in progress while performing unified ISSU.
IP | ✓ | – | –
IPv6 | ✓ | – | IPv6 is ISSU safe and compliant.
IPSec Transport (E120 and E320) | – | ✓ | E120 and E320 routers do not support IPSec.
IPSec Transport (ERX1440) | – | – | –
IPSec Tunnels (E120 and E320) | – | ✓ | E120 and E320 routers do not support IPSec.
IPSec Tunnels (ERX1440) | – | – | –
IS-IS | ✓ | – | Support only when graceful restart is configured.
OSPF | ✓ | – | Support only when graceful restart is configured.
RIP | ✓ | – | –
Static Routes | ✓ | – | –
Telnet | ✓ | – | Authentication and command authorizations on Telnet sessions fail during the upgrade phase and Telnet sessions are dropped.
IPv4 Multicast Routing |  |  |
Multicast Routing | ✓ | – | –
ANCP (L2C) | ✓ | – | Unified ISSU can proceed if ANCP is configured. However, ANCP has no graceful restart extensions and therefore it cannot maintain its dynamic state across the upgrade. Consequently, all ANCP sessions are brought down and then restored when the upgrade is completed.
DVMRP (E120 and E320) | ✓ | – | –
DVMRP (ERX1440) | – | – | –
IGMP | ✓ | – | –
PIM | ✓ | – | –
IPv6 Multicast Routing |  |  |
Multicast Routing | – | ✓ | IPv6 routing protocols are unified ISSU safe, but do not support ISSU.
MLD | – | ✓ | IPv6 routing protocols are unified ISSU safe, but do not support ISSU.
PIM | – | ✓ | IPv6 routing protocols are unified ISSU safe, but do not support ISSU.
Multiprotocol Label Switching |  |  |
MPLS | ✓ | – | –
BGP signaling | ✓ | – | –
LDP signaling | ✓ | – | –
RSVP-TE signaling | ✓ | – | –
Local cross-connects between layer 2 interfaces using MPLS | ✓ | – | –
Policies and QoS |  |  |
Policies | ✓ | – | –
QoS | ✓ | – | –
Remote Access |  |  |
AAA | ✓ | – | The following configuration is not supported: The subscriber username and password are on an ATM circuit in Bridged Ethernet over ATM or IP over ATM configurations.
DHCP External Server and Packet Trigger | ✓ | – | –
DHCP Packet Capture | ✓ | – | Configuration of DHCP packet capture does not prevent unified ISSU from proceeding. However, the capturing of packets on the line modules is halted when the unified ISSU upgrade phase commences. Packet capture resumes automatically during the unified ISSU service restoration phase.
DHCP Proxy Client | – | ✓ | –
DHCP Relay Proxy | ✓ | – | DHCP relay proxy continues processing of DHCP release requests during the unified ISSU to maintain server-client synchronization. State is preserved across the upgrade; statistics are not preserved.
DHCP Relay Server | ✓ | – | –
DHCPv4 Local Server | ✓ | – | Forwarding outages that take place during a unified ISSU can affect DHCP lease renewal. Before you begin unified ISSU, we recommend that you configure the DHCP local server address pools with a minimum lease time of 120 minutes to ensure that leases do not expire during the upgrade.
DHCPv6 Local Server | ✓ | – | IPv6 is ISSU safe and compliant. You can upgrade ISSU when DHCPv6 local server applications are configured. However, during the ISSU upgrade, new requests for IPv6 prefixes are blocked by the DHCPv6 local server.
L2TP | ✓ | – | Unified ISSU forces an L2TP failover for all established tunnels. L2TP failover resynchronization is required for successful recovery of a tunnel and its sessions following the upgrade.
L2TP Dialout | – | ✓ | –
IPv4 Local Address Pools | ✓ | – | –
IPv6 Local Address Pools | ✓ | – | IPv6 is ISSU safe and compliant. You can upgrade ISSU when IPv6 local address pool applications are configured on the server.
Local Authentication Server | ✓ | – | –
RADIUS Client | ✓ | – | –
RADIUS Dynamic-Request Server | ✓ | – | –
RADIUS Initiated Disconnect | ✓ | – | –
RADIUS Relay Server | – | ✓ | –
RADIUS Route-Download Server | ✓ | – | –
SRC Client | ✓ | – | –
Service Manager | ✓ | – | –
Subscriber Manager | ✓ | – | –
TACACS+ | ✓ | – | –
Miscellaneous |  |  |
Bulk statistics | ✓ | – | –
Denial of Service (DoS) protection | ✓ | – | –
HTTP server | ✓ | – | –
IOA hot swap | – | ✓ | –
J-Flow (IP flow statistics) | ✓ | – | –
Line Module Redundancy | ✓ | – | You can use the active spare line module for unified ISSU operations. You do not have to revert to the primary line module. The following sets of line modules and IOAs are supported: ATM: OC3-4A, OC3/OC12/DS3-ATM POS: OC3-4P Line Modules ES2 4G LM ES2 10G Uplink LM ES2 10G LM ES2 10G ADV LM IOAs ES2-S1 GE-4 IOA ES2-S1 GE-8 IOA ES2-S3 GE-20 IOA ES2-S1 10GE IOA ES2-S2 10GE PR IOA ES2-S1 OC3-8 STM1 ATM IOA ES2-S1 OC12-2 STM4 ATM IOA ES2-S1 OC12-2 STM4 POS IOA ES2-S1 OC48 STM16 POS IOA
Mobile IP Home Agent | – | ✓ | –
Network Address Translation (NAT) | – | ✓ | You must remove the NAT license configuration as well as the NAT configuration from the router.
NTP | ✓ | – | –
Resource Threshold Monitor | ✓ | – | –
Response Time Reporter | ✓ | – | –
Route Policy | ✓ | – | –
SNMP | ✓ | – | –
Subscriber Interfaces | ✓ | – | –
Tunnels (GRE and DVMRP) | ✓ | – | –
VRRP | ✓ | – | –

#### Related Documentation

- Unexpected AAA Authentication and Authorization Behavior During Unified ISSU
- Unexpected ATM Behavior During Unified ISSU
- Unexpected DHCP Behavior During Unified ISSU
- Unexpected Denial-of-Service Protection Behavior During Unified ISSU
- Unexpected Ethernet Behavior During Unified ISSU
- Unexpected File Transfer Protocol Server Behavior During Unified ISSU
- IS-IS Effects on Graceful Restart and Network Stability During Unified ISSU
- Unexpected L2TP Failover of Established Tunnels During Unified ISSU
- Interruption in Traffic Forwarding for Layer 3 Routing Protocols During Unified ISSU
- OSPF Effects on Graceful Restart and Network Stability During Unified ISSU
- Unexpected Suspension of PIM During Unified ISSU
- Unexpected SONET and SDH Behavior During Unified ISSU
- Unexpected T3 Behavior During Unified ISSU
- Unexpected Suspension of Subscriber Login and Logouts During Unified ISSU
- Unavailability of TACACS+ Services During Unified ISSU
- Recommended Settings for Routing Protocol Timers During Unified ISSU