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3
Cisco IOS XE 3S Release Notes for the Cisco ASR 903 Router
OL-26630-08
Chapter
Limitations and Restrictions
Equal Cost Multipath Limitation
•
The ASR 903 supports a maximum of 4 Equal Cost Multipath (ECMP) links.
Ethernet IM Limitations
•
The Cisco ASR 903 Router does not support the Facilities Data Link (FDL) on Ethernet interfaces.
• The Cisco ASR 903 Router does not support the mac-address command on Gigabit Ethernet
interface modules.
•
10 Gigabit Ethernet interface modules are not supported in slots 4 and 5.
• When you install a Gigabit Ethernet IM in the topmost interface module slot (slot 5), the last
interface (interface GigabitEthernet0/5/0) is not operational; the port is reserved for internal
communication.
•
When you configure the copper and SFP Gigabit Ethernet interface modules on a router with
redundant RSPs, the
speed and duplex commands are not visible in interface configuration mode
until you apply a shutdown / no shutdown to the interface.
• LACP Fast-Switchover Limitation—Cisco IOS has a default carrier-delay value of 2 seconds. When
an LACP link fails, the router does not perform a switchover until the carrier-delay timer expires.
The
carrier-delay command helps reduce this value. We recommend that you set a carrier-delay
value of greater than 0 as this value can result in slower convergence times. We also recommend that
you set an identical
carrier-delay value on all LACP member links.
MLPPP Limitations
The following limitations apply when using MLPPP on the Cisco ASR 903 Router:
•
All links in an MLPPP bundle must be on the same interface module.
•
All links in an MLPPP bundle must be of the same bandwidth.
•
The Cisco ASR 903 Router supports a maximum of 8 links per bundle
• To change the MLPPP bundle fragmentation mode between enabled and disabled, perform a
shutdown / no shutdown on the bundle.
•
LFI is not supported
• Multiclass MLP is not supported
•
The Cisco ASR 903 Router supports MLPPP statistics with the following limitations:
–
Packet counters on the bundle display the number of fragments rather than packets.
–
Control packets are accounted on the bundle.
•
If you increase the maximum transmission unit (MTU) size on an MLPPP interface to a value higher
than the maximum received reconstructed unit (MRRU) value on the peer interface, this can bring
the MLPPP tunnel down. To restore the tunnel, perform a shutdown/no shutdown on the interface.
MPLS VPN Limitation
•
MPLS VPN (L3VPN) Fragmentation does not function properly if an access interface has a higher
MTU value than a core interface. To ensure that fragmentation functions correctly, configure the
core interface MTU with a value that exceeds the access interface MTU and relevant headers.
OC-3 IM Limitations
•
SDH framing mode is supported; SONET is not supported.
•
The optical interface module is designed for OC-3 and OC-12 traffic, but OC-12 functionality is not
currently supported.