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

Table 48: Application Support for Unified In-Service Software Upgrades

Application | Supported | Unsupported | Notes
--- | --- | --- | ---
Physical Layer Protocols |  |  |
DS1 (E120 and E320) | ✓ | – | –
DS1 (ERX-1440) | – |  | –
DS3 | ✓ | – | –
HDLC | ✓ | – | –
SONET/SDH | ✓ | – | 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 | – | ✓ | Unified ISSU does not support IPv6.
IPSec Transport (E120 and E320) | Not applicable | Not applicable | E120 and E320 routers do not support IPSec.
IPSec Transport (ERX-1440) | – |  | –
IPSec Tunnels (E120 and E320) | Not applicable | Not applicable | E120 and E320 routers do not support IPSec.
IPSec Tunnels (ERX-1440) | – |  | –
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 (ERX-1440) | – |  | –
IGMP | ✓ | – | –
PIM | ✓ | – | –
IPv6 Multicast Routing |  |  |
Multicast Routing | – | ✓ | Unified ISSU does not support IPv6.
MLD | – | ✓ | Unified ISSU does not support IPv6.
PIM | – | ✓ | Unified ISSU does not support IPv6.
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 | – | ü | –
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 | – | ✓ | Unified ISSU does not support IPv6.
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 | – | ✓ | –
Local Address Pools | ✓ | – | –
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 are supported: ATM: OC3-4A, OC3/OC12/DS3-ATM POS: OC3-4P
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 | ✓ | – | –

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