Cisco ASR 900 Series Release Notes page 155

Chapter
When you install a Gigabit Ethernet IM in the topmost interface module slot (slot 5), the last
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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
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redundant RSPs, the speed and duplex commands are not visible in interface configuration mode
until you apply a shutdown/no shutdown to the interface.
Fragmentation is not supported with Multicast traffic.
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IPv6 Limitations
The following limitation applies when using IPv6 on the Cisco ASR 903 Router:
IPv6 Neighbor Discovery (ND) cache timer expiry is 4 hours. To prevent the neighbour adjacency
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from being deleted after the timer expires:
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IS-IS Limitations
IS-IS over IPv6 is not supported on VRF instances.
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Only one IS-IS process is permitted when you configure IS-IS with the address-family ipv6 and
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bfd-all-interfaces commands.
• The IS-IS total and per-stream convergence time increases as the number of prefixes increases.
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.
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All links in an MLPPP bundle must be of the same bandwidth.
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The Cisco ASR 903 Router supports a maximum of 8 links per bundle
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To change the MLPPP bundle fragmentation mode between enabled and disabled, perform a
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shutdown/no shutdown on the bundle.
LFI is not supported
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Multiclass MLP is not supported
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The Cisco ASR 903 Router supports MLPPP statistics with the following limitations:
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If you increase the maximum transmission unit (MTU) size on an MLPPP interface to a value higher
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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
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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.
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configure hardware based BFD sessions with the neighbours, or
configure static IPv6 neighbours, or
configure the ipv6 nd cache expire timer refresh command.
Packet counters on the bundle display the number of fragments rather than packets.
Control packets are accounted on the bundle.
Cisco IOS XE 3S Release Notes for the Cisco ASR 903 Router
Limitations and Restrictions
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