Alcatel-Lucent 5620 Troubleshooting Manual page 235

However, the typical L2 or L3 interface MTU on a 5620 SAM-managed device is likely
configured to transmit smaller SNMP packets, usually in the 1500-byte range. This
causes packet fragmentation. In order to handle these fragmented packets,
intermediate devices between the 5620 SAM- managed device and 5620 SAM must be
configured to handle or forward fragmented packets. When an intermediate network
device, such as a router, cannot handle or forward fragmented packets, then packets
may be dropped and resynchronization may fail. Consider the following.
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Alcatel-Lucent 5620 Service Aware Manager, Release
3HE 05723 AAAD TQZZA Edition 01
Ensure that devices located between the managed devices, such as the
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7750 SR, and the 5620 SAM can handle an MTU size of 9216 bytes, can fragment
large SNMP packets, or can forward fragmented L2 or L3 packets
Verify the MTU packet sizes for all LAN devices.
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Verify that large packets can travel from the managed devices to the 5620 SAM
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by using CLI to ping the IP address of the 5620 SAM server, with a large packet.
Ensure that the firewalls between the managed devices and the 5620 SAM
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server are configured to allow traceroute and ping packets.
Log in to the 7750 SR or another 5620 SAM-managed device.
Run the traceroute command:
> traceroute SAM_server_IP_address ↵
A list of hops and IP addresses appears.
Ping the first hop in the route from the managed device to the 5620 SAM server:
> ping intermediate_device_IP_address size 9216 ↵
A successful response indicates that the intermediate device supports large SNMP
packets or packet fragmentation.
Repeat for all other hops until a ping fails or until a message indicates that there
is an MTU mismatch. A failed ping indicates that the intermediate device does not
support large SNMP packets or packet fragmentation.
Check the configuration of the intermediate device, and configure fragmentation
or enable a larger MTU size.
Troubleshooting Guide
7 — Troubleshooting network management LAN issues
8.0 R4 Aug 2010
7-5